James T Schwiegerling

Interests

Research

Ophthalmic instrument design, diffractive and extended depth of focus lens design, aberration theory, optimization, schematic eye modeling, image simulation, freeform optics.

Teaching

Geometrical Optics, Optical specification, fabrication and testing, Visual Optics, Computational Photography and Linear Algebra

Courses

Scholarly Contributions

Books

• Schwiegerling, J. T. (2014). Optical Specification, Fabrication and Testing.

Chapters

• Schwiegerling, J. T. (2017). Geometrical optics. In Handbook of Visual Optics. Boca Raton, Florida: Taylor & Francis.
• Schwiegerling, J. T. (2017). The human eye and its aberrations. In Handbook of Optical Engineering, 2nd Edition. Boca Raton, Florida: CRC Press.

Journals/Publications

• McCafferty, S. J., Enikov, E. T., Schwiegerling, J., & Ashley, S. M. (2018). Goldmann tonometry tear film error and partial correction with a shaped applanation surface. Clinical ophthalmology (Auckland, N.Z.), 12, 71-78.
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  The aim of the study was to quantify the isolated tear film adhesion error in a Goldmann applanation tonometer (GAT) prism and in a correcting applanation tonometry surface (CATS) prism.
• McCafferty, S., Levine, J., Schwiegerling, J., & Enikov, E. T. (2018). Goldmann and error correcting tonometry prisms compared to intracameral pressure. BMC ophthalmology, 18(1), 2.
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  Compare Goldmann applanation tonometer (GAT) prism and correcting applanation tonometry surface (CATS) prism to intracameral intraocular pressure (IOP), in vivo and in vitro.
• Amirsolaimani, B., Peyman, G., Schwiegerling, J., Bablumyan, A., & Peyghambarian, N. (2017). A new low-cost, compact, auto-phoropter for refractive assessment in developing countries. Scientific reports, 7(1), 13990.
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  Using a phoropter to measure the refractive error is one of the most commonly used methods by ophthalmologists and optometrists. Here, we demonstrate design and fabrication of a portable automatic phoropter with no need for patient's feedback. The system is based on three tunable-focus fluidic lenses and thin-film holographic optical elements to perform automatic refractive error measurement and provide a diagnostic prescription without supervision. Three separate lenses are deployed to correct the defocus and astigmatism. The refractive error is measured using a Shack-Hartmann wavefront sensor that calculates the Zernike values of an infrared wavefront emerging from the eye. Holographic optical elements steer the emerging wavefront into the wavefront sensor, while simultaneously providing an unobstructed view for the subject. The power of each lens is controlled by pumping a liquid in and out of the lens chamber using servo motor actuated diaphragm pumps. Spherical and cylindrical correction range of -10 to +10 diopters with 0.1 diopter increments is achieved in less than 15 seconds using wavefront sensor feedback to the pumps. This system can be used in rapid screening of large patient populations especially in the developing countries that lack sufficient facilities and specialist doctors.
• McCafferty, S., Levine, J., Schwiegerling, J., & Enikov, E. T. (2017). Goldmann applanation tonometry error relative to true intracameral intraocular pressure in vitro and in vivo. BMC ophthalmology, 17(1), 215.
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  Goldmann applanation tonometry (GAT) error relative to intracameral intraocular pressure (IOP) has not been examined comparatively in both human cadaver eyes and in live human eyes. Futhermore, correlations to biomechanical corneal properties and positional changes have not been examined directly to intracameral IOP and GAT IOP.
• McCafferty, S., Lim, G., Duncan, W., Enikov, E. T., Schwiegerling, J., Levine, J., & Kew, C. (2017). Goldmann tonometer error correcting prism: clinical evaluation. Clinical ophthalmology (Auckland, N.Z.), 11, 835-840.
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  Clinically evaluate a modified applanating surface Goldmann tonometer prism designed to substantially negate errors due to patient variability in biomechanics.
• Schwiegerling, J. (2017). Relating wavefront error, apodization, and the optical transfer function: general case. Journal of the Optical Society of America. A, Optics, image science, and vision, 34(5), 726-731.
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  In a previous paper, a technique was developed for decomposing the incoherent optical transfer function (OTF) into a linear combination of basis functions [J. Opt. Soc. Am. A31, 2476 (2014)JOAOD60740-323210.1364/JOSAA.31.002476]. The expansion coefficients for the OTF are directly related to wavefront error coefficients and apodization factors. This earlier work assumed rotational symmetry, so that only the on-axis wavefront error components, defocus and various orders of spherical aberration, and rotationally symmetric apodization were handled. In this paper, the technique is generalized to handle arbitrary wavefront errors and apodization. Analytic expressions for the basis functions as well as an example expansion are provided.
• Vinas, M., Dorronsoro, C., Radhakrishnan, A., Benedi-Garcia, C., LaVilla, E. A., Schwiegerling, J., & Marcos, S. (2017). Comparison of vision through surface modulated and spatial light modulated multifocal optics. Biomedical optics express, 8(4), 2055-2068.
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  Spatial-light-modulators (SLM) are increasingly used as active elements in adaptive optics (AO) systems to simulate optical corrections, in particular multifocal presbyopic corrections. In this study, we compared vision with lathe-manufactured multi-zone (2-4) multifocal, angularly and radially, segmented surfaces and through the same corrections simulated with a SLM in a custom-developed two-active-element AO visual simulator. We found that perceived visual quality measured through real manufactured surfaces and SLM-simulated phase maps corresponded highly. Optical simulations predicted differences in perceived visual quality across different designs at Far distance, but showed some discrepancies at intermediate and near.
• Mahamat, A. H., Narducci, F. A., & Schwiegerling, J. (2016). Design and optimization of a volume-phase holographic grating for simultaneous use with red, green, and blue light using unpolarized light. Applied optics, 55(7), 1618-24.
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  Volume-phase holographic (VPH) gratings have been designed for use in many areas of science and technology, such as optical communication, optical imaging, and astronomy. In this paper, the design of a volume-phase holographic grating, simultaneously optimized to operate in the red, green, and blue wavelengths, is presented along with a study of its fabrication tolerances. The grating is optimized to produce 98% efficiency at λ=532  nm and at least 75% efficiency in the region between 400 and 700 nm, when the incident light is unpolarized. The optimization is done for recording in dichromated gelatin with a thickness of 12 μm, an average refractive index of 1.5, and a refractive index modulation of 0.022.
• McCafferty, S., Lim, G., Duncan, W., Enikov, E., & Schwiegerling, J. (2016). Goldmann Tonometer Prism with an Optimized Error Correcting Applanation Surface. Translational vision science & technology, 5(5), 4.
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  We evaluate solutions for an applanating surface modification to the Goldmann tonometer prism, which substantially negates the errors due to patient variability in biomechanics.
• Schwiegerling, J. (2016). Relating wavefront error, apodization, and the optical transfer function: on-axis case: reply. Journal of the Optical Society of America. A, Optics, image science, and vision, 33(8), 1626-7.
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  Efficient coding enables rapid calculation of basis functions for a linear expansion of the optical transfer function.
• Werner, L., Stover, J. C., Schwiegerling, J., & Das, K. K. (2016). Effects of Intraocular Lens Opacification on Light Scatter, Stray Light, and Overall Optical Quality/Performance. Investigative ophthalmology & visual science, 57(7), 3239-47.
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  To evaluate light scatter and stray light in intraocular lenses (IOLs) explanted because of postoperative opacification (13 calcified hydrophilic acrylic, 1 calcified silicone, and 4 polymethylmethacrylate [PMMA] lenses with snowflake degeneration), as well as effect of opacification on other optical quality/performance indicators, in comparison with controls.
• Werner, L., Stover, J. C., Schwiegerling, J., & Das, K. K. (2016). Light scattering, straylight, and optical quality in hydrophobic acrylic intraocular lenses with subsurface nanoglistenings. Journal of cataract and refractive surgery, 42(1), 148-56.
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  To evaluate forward light scattering and straylight in single-piece hydrophobic acrylic intraocular lenses (IOLs) (Acrysof) removed from cadaver eyes and design- and power-matched controls, as well as the effect of subsurface nanoglistenings on other optical quality and performance indicators.
• McCafferty, S. J., & Schwiegerling, J. T. (2015). Deformable Surface Accommodating Intraocular Lens: Second Generation Prototype Design Methodology and Testing. Translational vision science & technology, 4(2), 17.
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  Present an analysis methodology for developing and evaluating accommodating intraocular lenses incorporating a deformable interface.
• Miller, J. M., Harvey, E. M., & Schwiegerling, J. (2015). Higher-order aberrations and best-corrected visual acuity in Native American children with a high prevalence of astigmatism. Journal of AAPOS : the official publication of the American Association for Pediatric Ophthalmology and Strabismus / American Association for Pediatric Ophthalmology and Strabismus, 19(4), 352-7.e1.
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  To determine whether higher-order aberrations (HOAs) in children from a highly astigmatic population differ from population norms and whether HOAs are associated with astigmatism and reduced best-corrected visual acuity.
• Steinert, R. F., Schwiegerling, J., Lang, A., Roy, A., Holliday, K., Barragán Garza, E., & Chayet, A. S. (2015). Range of refractive independence and mechanism of action of a corneal shape-changing hydrogel inlay: results and theory. Journal of cataract and refractive surgery, 41(8), 1568-79.
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  To demonstrate the independence of visual performance over a range of preoperative refraction and age in presbyopes implanted with a corneal shape-changing inlay (Raindrop Near Vision Inlay).
• Cole, S. C., Werner, L., Schwiegerling, J., & Crandall, A. (2014). Visual aberrations in a multifocal intraocular lens with injection-related scratches. Journal of cataract and refractive surgery, 40(11), 1913-8.
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  We describe the case of a 70-year-old woman who had phacoemulsification and implantation of a single-piece hydrophobic acrylic multifocal intraocular lens (IOL). Following surgery, the patient experienced blurring, positive dysphotopsia, impaired night vision, and glare. After 2 years, optic damage likely related to the IOL injection procedure was noted. The IOL was successfully exchanged. The uncorrected distance visual acuity was 20/20, and the patient reported no further visual aberrations. Gross and microscopic examination revealed large linear scratches on the central part of the optic. Scheimpflug photography with densitometry analysis of the area of the anterior scratches revealed extremely high levels of surface backlight scattering (227 computer-compatible tape units). Modulation transfer function and Badal images of the explanted IOL and of a control IOL did not differ significantly. This report suggests that severe defects/damage such as those described would likely be clinically significant in IOLs with specialized optics and warrant immediate removal/exchange of a damaged multifocal IOL.
• Schwiegerling, J. (2014). Relating wavefront error, apodization, and the optical transfer function: on-axis case. Journal of the Optical Society of America. A, Optics, image science, and vision, 31(11), 2476-83.
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  The incoherent optical transfer function (OTF) describes contrast degradation and phase shifts of sinusoidal objects of all spatial frequencies and orientations. The OTF is calculated as either an autocorrelation of the pupil function or the Fourier transform of the point spread function. Even with fast algorithms, these calculations can be slow for a densely sampled pupil. Here, a linear expansion of the OTF is developed in which the expansion coefficients are related to the wavefront error and apodization coefficients. The advantage of such a representation is that the OTF can be quickly generated from parameters of the optical system.
• Schwiegerling, J. T. (2014). Photostress Testing Device for Diagnosing Retinal Disease. Photonics.
• Das, K. K., Stover, J. C., Schwiegerling, J., & Karakelle, M. (2013). Technique for measuring forward light scatter in intraocular lenses. Journal of Cataract and Refractive Surgery, 39(5), 770-778.
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  PMID: 23395325;Abstract: Purpose: To develop a technique for measuring the forward light scattering of intraocular lenses (IOLs). Setting: The Scatter Works, Tucson, Arizona, USA. Design: Evaluation of diagnostic technique. Methods: A scatterometer with laser sources of 488 nm and 633 nm was used to directly measure the forward-scattered light of IOLs. These sources illuminated balanced salt solution-immersed IOLs within a cylindrical wet cell. The wet cell was placed at the center of rotation of a goniometer arm. On the end of the arm was a detector that measured the amount of laser light scattered from the IOL as a function of incident-beam angle. The measurements provided a profile of the scatter distribution for regions outside the directly transmitted beam. Forward and back light scatter was measured in new and artificially aged IOLs. Results: Forward light scatter was increased in artificially aged IOLs compared with that in new unaged IOLs. The artificially aged IOLs developed sub-wavelength-diameter water nanoglistenings in the bulk material just below the surface. The measured scatter profiles were consistent with these subsurface droplets, suggesting Rayleigh-type scatter in the aged IOLs. The amount of light scatter from nanoglistenings does not appear to be sufficient to impair vision. Although the severely aged IOLs showed increased scatter, the level of increase was within 1 standard deviation of what is found in the normal population. Conclusion: A technique was developed enabling quantification of forward-scattered and back-scattered light from IOLs. Financial Disclosure: Drs. Das and Karakelle are employees of Alcon Laboratories, Inc. Dr. Stover has received consultant fees and Dr. Schwiegerling research funding from Alcon Laboratories, Inc. © 2013 ASCRS and ESCRS.
• Harvey, E. M., Miller, J. M., & Schwiegerling, J. (2013). Utility of an open field Shack-Hartmann aberrometer for measurement of refractive error in infants and young children. Journal of AAPOS : the official publication of the American Association for Pediatric Ophthalmology and Strabismus / American Association for Pediatric Ophthalmology and Strabismus, 17(5), 494-500.
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  To assess the utility of an open-field Shack-Hartmann aberrometer for measurement of refractive error without cycloplegia in infants and young children.
• Harvey, E. M., Miller, J. M., & Schwiegerling, J. (2013). Utility of an open field Shack-Hartmann aberrometer for measurement of refractive error in infants and young children. Journal of AAPOS, 17(5), 494-500.
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  PMID: 24160970;PMCID: PMC3881277;Abstract: Purpose To assess the utility of an open-field Shack-Hartmann aberrometer for measurement of refractive error without cycloplegia in infants and young children. Method Data included 2698 subject encounters with Native American infants and children aged 6 months to
• Harvey, E. M., Miller, J. M., Schwiegerling, J., Sherrill, D., Messer, D. H., & Dobson, V. (2013). Developmental changes in anterior corneal astigmatism in Tohono O'odham Native American infants and children. Ophthalmic Epidemiology, 20(2), 102-108.
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  PMID: 23510314;Abstract: Purpose: To describe change in corneal astigmatism in infants and children of a Native American tribe with a high prevalence of astigmatism. Methods: Longitudinal measurements of corneal astigmatism were obtained in 960 Tohono O'odham children aged 6 months to
• Harvey, E. M., Miller, J. M., Schwiegerling, J., Sherrill, D., Messer, D. H., & Dobson, V. (2013). Developmental changes in anterior corneal astigmatism in Tohono O'odham Native American infants and children. Ophthalmic epidemiology, 20(2), 102-8.
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  ABSTRACT Purpose: To describe change in corneal astigmatism in infants and children of a Native American tribe with a high prevalence of astigmatism.
• Savidis, N., Peyman, G., Peyghambarian, N., & Schwiegerling, J. (2013). Nonmechanical zoom system through pressure-controlled tunable fluidic lenses. Applied Optics, 52(12), 2858-2865.
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  PMID: 23669698;Abstract: We have developed a variable-power zoom system that incorporates fluidic lenses and has no moving parts. The designed system applies two single-chamber plano-convex fluid singlets, each with their own distinct design, as well as a conventional refractive lens. In this paper, we combine the two fluid elements to form a variable-power telescope, while the fixed lens enables image formation. In this configuration, the image plane location is fixed. By synchronizing the powers of the two fluidic lenses, we produce a varying magnification zoom system. The design of each lens and the coupled system is analyzed. The coupled device experimentally produced a magnification range of 0.1× to 10× zoom or a 20× zoom magnification range with no moving parts. Furthermore, we expand on optical performance and capabilities of our system with fluidic lenses relative to traditional zoom lenses. ©2013 Optical Society of America.
• Schwiegerling, J. T. (2013). Eye axes and their relevance to alignment of corneal refractive procedures. Journal of Refractive Surgery, 29(8), 515-516.
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  PMID: 23909777;
• Schwiegerling, J., & Schwiegerling, J. T. (0). Modal reconstruction methods with Zernike polynomials. Journal of refractive surgery (Thorofare, N.J. : 1995), 21(5).
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  To compare the advantages and disadvantages of different techniques for fitting Zernike polynomials to surfaces.
• Schwiegerling, J., & Schwiegerling, J. T. (0). Theoretical limits to visual performance. Survey of ophthalmology, 45(2).
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  Wavefront sensors and scanning laser technology are enabling the correction of the aberrations of the eye. The effects of aberrations on visual performance are reviewed, and the theoretical limit of visual performance is predicted to understand the ultimate endpoint of these new technologies. A schematic eye model that incorporates diffraction, chromatic aberration, photopic response, the Stiles-Crawford effect, and pupil size is ray-traced to determine its limiting optical properties. These properties are compared to the detection requirements of the retina and brain to determine the theoretical limit of foveal vision. The theoretical limits on foveal vision are found to be between 20/12 and 20/5, depending on pupil diameter. It is concluded that emerging refractive surgery technologies may provide substantial increases in visual performance.
• Schwiegerling, J., Savidis, N., Peyman, G., Peyghambarian, N., & Schwiegerling, J. T. (2013). Nonmechanical zoom system through pressure-controlled tunable fluidic lenses. Applied optics, 52(12).
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  We have developed a variable-power zoom system that incorporates fluidic lenses and has no moving parts. The designed system applies two single-chamber plano-convex fluid singlets, each with their own distinct design, as well as a conventional refractive lens. In this paper, we combine the two fluid elements to form a variable-power telescope, while the fixed lens enables image formation. In this configuration, the image plane location is fixed. By synchronizing the powers of the two fluidic lenses, we produce a varying magnification zoom system. The design of each lens and the coupled system is analyzed. The coupled device experimentally produced a magnification range of 0.1× to 10× zoom or a 20× zoom magnification range with no moving parts. Furthermore, we expand on optical performance and capabilities of our system with fluidic lenses relative to traditional zoom lenses.
• Davison, J. A., Patel, A. S., Cunha, J. P., Schwiegerling, J., & Muftuoglu, O. (2012). Reply to letter from Mainster M.A. and Turner P.L. titled "blue light's benefits vs blue-blocking intraocular lens chromophores". Graefe's Archive for Clinical and Experimental Ophthalmology, 250(8), 1247-1248.
• McCafferty, S. J., Schwiegerling, J. T., & Enikov, E. T. (2012). Corneal surface asphericity, roughness, and transverse contraction after uniform scanning excimer laser ablation. Investigative ophthalmology & visual science, 53(3), 1296-305.
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  To examine the interaction between the excimer laser and residual tissue.
• McCafferty, S. J., Schwiegerling, J. T., & Enikov, E. T. (2012). Thermal load from a CO2 laser radiant energy source induces changes in corneal surface asphericity, roughness, and transverse contraction. Investigative ophthalmology & visual science, 53(7), 4279-88.
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  We examined corneal surface response to an isolated thermal load.
• Schwiegerling, J. (2012). Tolerancing considerations for visual systems. Proceedings of SPIE - The International Society for Optical Engineering, 8491.
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  Abstract: In designing optical systems where the eye serves as the final detector, assumptions are typically made regarding the optical quality of the eye system. Often, the aberrations of the eye are ignored or minimal adjustments are built into the system under design to handle variations in defocus found within the human population. In general, the eye contains aberrations that vary randomly from person to person. In this investigation, a general technique for creating a random set of aberrations consistent with the statistics of the human eye is developed. These aberrations in turn can be applied to a schematic eye model and their effect on the combined visual instrument/eye system can be determined. Repeated application of different aberration patterns allows for tolerance analysis of performance metrics such of the modulation transfer function (MTF). © 2012 SPIE.
• Schwiegerling, J., Birch, G. C., Tyo, J. S., & Schwiegerling, J. T. (2012). Depth measurements through controlled aberrations of projected patterns. Optics express, 20(6).
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  Three-dimensional displays have become increasingly present in consumer markets. However, the ability to capture three-dimensional images in space confined environments and without major modifications to current cameras is uncommon. Our goal is to create a simple modification to a conventional camera that allows for three dimensional reconstruction. We require such an imaging system have imaging and illumination paths coincident. Furthermore, we require that any three-dimensional modification to a camera also permits full resolution 2D image capture.Here we present a method of extracting depth information with a single camera and aberrated projected pattern. A commercial digital camera is used in conjunction with a projector system with astigmatic focus to capture images of a scene. By using an astigmatic projected pattern we can create two different focus depths for horizontal and vertical features of a projected pattern, thereby encoding depth. By designing an aberrated projected pattern, we are able to exploit this differential focus in post-processing designed to exploit the projected pattern and optical system. We are able to correlate the distance of an object at a particular transverse position from the camera to ratios of particular wavelet coefficients.We present our information regarding construction, calibration, and images produced by this system. The nature of linking a projected pattern design and image processing algorithms will be discussed.
• Davison, J. A., Patel, A. S., Cunha, J. P., Schwiegerling, J., & Muftuoglu, O. (2011). Recent studies provide an updated clinical perspective on blue light-filtering IOLs. Graefe's Archive for Clinical and Experimental Ophthalmology, 249(7), 957-968.
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  PMID: 21584764;PMCID: PMC3124647;Abstract: Background: Recent reviews of blue light-filtering intraocular lenses (IOLs) have stated their potential risks for scotopic vision and circadian photoentrainment. Some authors have challenged the rationale for retinal photoprotection that these IOLs might provide. Our objective is to address these issues by providing an updated clinical perspective based on the results of the most recent studies. Methods: This article evaluates the currently available published papers assessing the potential risks and benefits of blue light-filtering IOLs. It summarizes the results of seven clinical and two computational studies on photoreception, and several studies related to retinal photoprotection, all of which were not available in the previous reviews. These results provide a clinical risk/benefit analysis for an updated review for these IOLs. Results: Most clinical studies comparing IOLs with and without the blue light-filtering feature have found no difference in clinical performance for; visual acuity, contrast sensitivity, color vision, or glare. For blue light-filtering IOLs, three comparative clinical studies have shown improved contrast sensitivity and glare reduction; but one study, while it showed satisfactory overall color perception, demonstrated some compromise in mesopic comparative blue color discrimination. Comparative results of two recent clinical studies have also shown improved performance for simulated driving under glare conditions and reduced glare disability, better heterochromatic contrast threshold, and faster recovery from photostress for blue light-filtering IOLs. Two computational and five clinical studies found no difference in performance between IOLs with or without blue light-filtration for scotopic vision performance and photo entrainment of the circadian rhythm. The rationale for protection of the pseudophakic retina against phototoxicity is discussed with supporting results of the most recent computational, in-vitro, animal, clinical, and epidemiological investigations. Conclusions: This analysis provides an updated clinical perspective which suggests the selection of blue light-filtering IOLs for patients of any age, but especially for pediatric and presbyopic lens exchange patients with a longer pseudophakic life. Without clinically substantiated potential risks, these patients should experience the benefit of overall better quality of vision, reduced glare disability at least in some conditions, and better protection against retinal phototoxicity and its associated potential risk for AMD. © 2011 The Author(s).
• Davison, J. A., Patel, A. S., Cunha, J. P., Schwiegerling, J., & Muftuoglu, O. (2011). Recent studies provide an updated clinical perspective on blue light-filtering IOLs. Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv für klinische und experimentelle Ophthalmologie, 249(7), 957-68.
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  Recent reviews of blue light-filtering intraocular lenses (IOLs) have stated their potential risks for scotopic vision and circadian photoentrainment. Some authors have challenged the rationale for retinal photoprotection that these IOLs might provide. Our objective is to address these issues by providing an updated clinical perspective based on the results of the most recent studies.
• Harvey, E. M., Dobson, V., Miller, J. M., Schwiegerling, J., Clifford-Donaldson, C. E., Green, T. K., & Messer, D. H. (2011). Prevalence of corneal astigmatism in Tohono O'odham Native American children 6 months to 8 years of age. Investigative Ophthalmology and Visual Science, 52(7), 4350-4355.
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  PMID: 21460261;PMCID: PMC3175958;Abstract: Purpose. To describe the prevalence of corneal astigmatism in infants and young children who are members of a Native American tribe with a high prevalence of refractive astigmatism. Methods. The prevalence of corneal astigmatism was assessed by obtaining infant keratometer (IK4) measurements from 1235 Tohono O'odham children, aged 6 months to 8 years. Results. The prevalence of corneal astigmatism >2.00 D was lower in the 1- to
• Harvey, E. M., Dobson, V., Miller, J. M., Schwiegerling, J., Clifford-Donaldson, C. E., Green, T. K., & Messer, D. H. (2011). Prevalence of corneal astigmatism in Tohono O'odham Native American children 6 months to 8 years of age. Investigative ophthalmology & visual science, 52(7), 4350-5.
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  To describe the prevalence of corneal astigmatism in infants and young children who are members of a Native American tribe with a high prevalence of refractive astigmatism.
• Harvey, E. M., Miller, J. M., Schwiegerling, J., Clifford-Donaldson, C. E., Green, T. K., Messer, D. H., & Dobson, V. (2011). Accuracy and validity of IK4 handheld video keratometer measurements in children. Journal of AAPOS, 15(4), 407-409.
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  PMID: 21907130;PMCID: PMC3172570;Abstract: The infant keratometer (IK4) is a custom handheld instrument that was designed specifically to allow measurement of corneal astigmatism in infants as young as 6 months of age. In this study, accuracy of IK4 measurements with the use of standard toric surfaces was within 0.25 D. Validity measurements obtained in 860 children aged 3-7 years demonstrated slightly greater astigmatism measurements in the IK4 than in the Retinomax K+. Measurement success was 98% when the IK4 was used. The IK4 may prove to be clinically useful for screening children as young as 3 years of age at high risk for corneal astigmatism. Copyright © 2011 Published by Elsevier Inc. on behalf of American Association for Pediatric Ophthalmology and Strabismus.
• Schwiegerling, J. (2011). Introduction to the 12th International Congress of Wavefront & Presbyopic Refractive Corrections. Journal of Refractive Surgery, 27(11), 832-.
• Schwiegerling, J. (2011). Scaling pseudo-zernike expansion coefficients to different pupil sizes. Optics Letters, 36(16), 3076-3078.
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  PMID: 21847165;Abstract: Orthogonal polynomials are routinely used to represent complex surfaces over a specified domain. In optics, Zernike polynomials have found wide application in optical testing, wavefront sensing, and aberration theory. This set is orthogonal over the continuous unit circle matching the typical shape of optical components and pupils. A variety of techniques has been developed to scale Zernike expansion coefficients to concentric circular subregions to mimic, for example, stopping down the aperture size of an optical system. Here, similar techniques are used to rescale the expansion coefficients to new pupil sizes for a related orthogonal set: the pseudo-Zernike polynomials. © 2011 Optical Society of America.
• Schwiegerling, J., & Schwiegerling, J. T. (2011). Scaling pseudo-Zernike expansion coefficients to different pupil sizes. Optics letters, 36(16).
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  Orthogonal polynomials are routinely used to represent complex surfaces over a specified domain. In optics, Zernike polynomials have found wide application in optical testing, wavefront sensing, and aberration theory. This set is orthogonal over the continuous unit circle matching the typical shape of optical components and pupils. A variety of techniques has been developed to scale Zernike expansion coefficients to concentric circular subregions to mimic, for example, stopping down the aperture size of an optical system. Here, similar techniques are used to rescale the expansion coefficients to new pupil sizes for a related orthogonal set: the pseudo-Zernike polynomials.
• Valley, P., Savidis, N., Schwiegerling, J., Dodge, M. R., Peyman, G., & Peyghambarian, N. (2011). Adjustable hybrid diffractive/refractive achromatic lens. Optics Express, 19(8), 7468-7479.
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  PMID: 21503055;PMCID: PMC3368326;Abstract: We demonstrate a variable focal length achromatic lens that consists of a flat liquid crystal diffractive lens and a pressure-controlled fluidic refractive lens. The diffractive lens is composed of a flat binary Fresnel zone structure and a thin liquid crystal layer, producing high efficiency and millisecond switching times while applying a low ac voltage input. The focusing power of the diffractive lens is adjusted by electrically modifying the sub-zones and re-establishing phase wrapping points. The refractive lens includes a fluid chamber with a flat glass surface and an opposing elastic polydimethylsiloxane (PDMS) membrane surface. Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position. Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at selected focal lengths. Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats. © 2011 Optical Society of America.
• Valley, P., Savidis, N., Schwiegerling, J., Dodge, M. R., Peyman, G., & Peyghambarian, N. (2011). Adjustable hybrid diffractive/refractive achromatic lens. Optics express, 19(8), 7468-79.
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  We demonstrate a variable focal length achromatic lens that consists of a flat liquid crystal diffractive lens and a pressure-controlled fluidic refractive lens. The diffractive lens is composed of a flat binary Fresnel zone structure and a thin liquid crystal layer, producing high efficiency and millisecond switching times while applying a low ac voltage input. The focusing power of the diffractive lens is adjusted by electrically modifying the sub-zones and re-establishing phase wrapping points. The refractive lens includes a fluid chamber with a flat glass surface and an opposing elastic polydimethylsiloxane (PDMS) membrane surface. Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position. Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at selected focal lengths. Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats.
• Marks, R., Mathine, D. L., Peyman, G., Schwiegerling, J., & Peyghambarian, N. (2010). Adjustable adaptive compact fluidic phoropter with no mechanical translation of lenses. Optics Letters, 35(5), 739-741.
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  PMID: 20195337;PMCID: PMC2845967;Abstract: We demonstrate a compact optical phoroptor consisting of adjustable astigmatic and defocus lenses. The lenses are fluidically controlled and allow for an arbitrary refractive error to be corrected without mechanically moving lenses. Shack-Hartmann measurements were used to characterize the optical properties of the individual lenses. The lenses were then assembled into the phoropter and controlled with three separate fluid controls. The phoroptor was verified by correcting the vision of a model eye with an induced refraction error. © 2010 Optical Society of America.
• Marks, R., Mathine, D. L., Peyman, G., Schwiegerling, J., & Peyghambarian, N. (2010). Adjustable adaptive compact fluidic phoropter with no mechanical translation of lenses. Optics letters, 35(5), 739-41.
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  We demonstrate a compact optical phoroptor consisting of adjustable astigmatic and defocus lenses. The lenses are fluidically controlled and allow for an arbitrary refractive error to be corrected without mechanically moving lenses. Shack-Hartmann measurements were used to characterize the optical properties of the individual lenses. The lenses were then assembled into the phoropter and controlled with three separate fluid controls. The phoroptor was verified by correcting the vision of a model eye with an induced refraction error.
• Schwiegerling, J. (2010). Introduction to the 11th International Congress of Wavefront & Presbyopic Refractive Corrections. Journal of Refractive Surgery, 26(10), 771-.
• Schwiegerling, J. (2010). Predicting clinical visual acuity of presbyopia treatments. Journal of Refractive Surgery, 26(1), 66-70.
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  PMID: 20199016;Abstract: PURPOSE: To predict the potential clinical visual acuity of different presbyopia treatments. METHODS: The defocus transfer function (DTF) is a mathematical technique for simultaneously illustrating the optical transfer function for all levels of defocus. Through-focus clinical visual acuity measurements were superimposed onto the DTF to determine the corresponding retinal contrast and map out a modulation threshold curve. The process is performed for an apodized diffractive and a zonal refractive intraocular lens, as well as an opaque annular ring implant that extends depth of focus. RESULTS: Clinical visual acuity measurements appear to track contours on the DTF. The elevation of these contours changes as a function of spatial frequency, with the general trend being that for higher spatial frequencies, more retinal contrast is needed to achieve a given level of visual acuity. The presence of these contours suggests a minimum level of retinal contrast is needed to achieve a given visual acuity, and if this threshold is exceeded, the presbyopia treatment can provide the corresponding acuity clinically. CONCLUSIONS: The DTF provides a global view of ocular performance for all object distances. The disparate technologies investigated all gave similar modulation threshold curves. These results suggest that the modulation threshold curve can be used to predict potential visual acuity of other multifocal lens designs and methods for treating presbyopia. Copyright ©SLACK Incorporated.
• Schwiegerling, J. (2010). Reply. Journal of Refractive Surgery, 26(8), 545-546.
• Schwiegerling, J., & DeHoog, E. (2010). Problems testing diffractive intraocular lenses with Shack-Hartmann sensors. Applied optics, 49(16), D62-8.
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  Shack-Hartmann wavefront sensors have found widespread application for testing ocular aberrations. These sensors provide an accurate map of the wavefront emerging from an eye in most cases. However, there is a growing class of patients with diffractive intraocular lenses that will potentially be measured incorrectly with Shack-Hartmann devices. We explore the pitfalls of measuring diffractive lenses with this technology.
• Schwiegerling, J., & Dehoog, E. (2010). Problems testing diffractive intraocular lenses with Shack-Hartmann sensors. Applied Optics, 49(16), D62-D68.
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  PMID: 20517360;Abstract: Shack-Hartmann wavefront sensors have found widespread application for testing ocular aberrations. These sensors provide an accurate map of the wavefront emerging from an eye in most cases. However, there is a growing class of patients with diffractive intraocular lenses that will potentially be measured incorrectly with Shack-Hartmann devices. We explore the pitfalls of measuring diffractive lenses with this technology. © 2010 Optical Society of America.
• Schwiegerling, J., & Schwiegerling, J. T. (2010). Predicting clinical visual acuity of presbyopia treatments. Journal of refractive surgery (Thorofare, N.J. : 1995), 26(1).
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  To predict the potential clinical visual acuity of different presbyopia treatments.
• Valley, P., Dodge, M. R., Schwiegerling, J., Mathine, D., Peyman, G., & Peyghambarian, N. (2010). Flat liquid crystal diffractive lenses with variable focus and magnification. Proceedings of SPIE - The International Society for Optical Engineering, 7786.
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  Abstract: Non-mechanical variable lenses are important for creating compact imaging devices. Various methods employing dielectrically actuated lenses, membrane lenses, and/or liquid crystal lenses were previously proposed1-4. Here we present tunable-focus flat liquid crystal diffractive lenses (LCDL) employing binary Fresnel zone electrodes fabricated on Indium-Tin-Oxide using conventional micro-photolithography. The phase levels can be adjusted by varying the effective refractive index of a nematic liquid crystal sandwiched between the electrodes and a reference substrate. Using a proper voltage distribution across various electrodes the focal length can be changed. Electrodes are shunted such that the correct phase retardation step sequence is achieved. If the number of 2π zone boundaries is increased by a factor of m the focal length is changed from f to f/m based on the digitized Fresnel zone equation: f = rm2/2mλ, where rm is mth zone radius, and λ is the wavelength. The lenses operate at very low voltage levels (±2.5V ac input), exhibit fast switching times (20-150 ms), can have large apertures (>10 mm), and small form factor, and are robust and insensitive to vibrations, gravity, and capillary effects that limit membrane and dielectrically actuated lenses. Several tests were performed on the LCDL including diffraction efficiency measurement, switching dynamics, and hybrid imaging with a refractive lens. Negative focal lengths are achieved by adjusting the voltages across electrodes. Using these lenses in combination, magnification can be changed and zoom lenses can be formed. The promising results make LCDL a good candidate for non-mechanical auto-focus and zoom lenses. © 2010 SPIE.
• Valley, P., Dodge, M. R., Schwiegerling, J., Peyman, G., & Peyghambarian, N. (2010). Nonmechanical bifocal zoom telescope. Optics Letters, 35(15), 2582-2584.
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  PMID: 20680065;Abstract: We report on a novel zoom lens with no moving parts in the form of a switchable Galilean telescope. This zoom telescope consists of two flat liquid-crystal diffractive lenses with apertures of 10 mm that can each take on the focal lengths of -50 and +100 cm, with a spacing of 50 cm and, hence, a zoom ratio of 4x. The lenses are driven using a low-voltage ac source with 1.6 V and exhibit millisecond switching times. The spectral characteristic of this diffractive zoom system is evaluated for light sources of various bandwidths. Potential applications for this technology include a zoom lens with no moving parts for camera phones and medical imaging devices. © 2010 Optical Society of America.
• Valley, P., Mathine, D. L., Dodge, M. R., Schwiegerling, J., Peyman, G., & Peyghambarian, N. (2010). Tunable-focus flat liquid-crystal diffractive lens. Optics Letters, 35(3), 336-338.
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  PMID: 20125713;Abstract: We demonstrate an innovative variable-focus flat liquid-crystal diffractive lens (LCDL) with 95% diffraction efficiency and millisecond switching times using a ±2.4 V ac input. This lens is based on the electrical modulation of a 3μm layer of nematic liquid-crystal sandwiched between a Fresnel zone electrode structure and a reference substrate. Each zone is divided into 12 subzones to digitize the phase profiles and define the phase wrapping points. The focusing power can rapidly be switched by electrically changing the number of subzones and re-establishing the wrapping points. Potential applications include zooms with no moving parts and autofocus lenses for compact imaging devices. © 2010 Optical Society of America.
• Valley, P., Mathine, D. L., Dodge, M. R., Schwiegerling, J., Peyman, G., & Peyghambarian, N. (2010). Tunable-focus flat liquid-crystal diffractive lens. Optics letters, 35(3), 336-8.
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  We demonstrate an innovative variable-focus flat liquid-crystal diffractive lens (LCDL) with 95% diffraction efficiency and millisecond switching times using a +/-2.4 V ac input. This lens is based on the electrical modulation of a 3 mum layer of nematic liquid-crystal sandwiched between a Fresnel zone electrode structure and a reference substrate. Each zone is divided into 12 subzones to digitize the phase profiles and define the phase wrapping points. The focusing power can rapidly be switched by electrically changing the number of subzones and re-establishing the wrapping points. Potential applications include zooms with no moving parts and autofocus lenses for compact imaging devices.
• Valley, P., Reza Dodge, M., Schwiegerling, J., Peyman, G., & Peyghambarian, N. (2010). Nonmechanical bifocal zoom telescope. Optics letters, 35(15), 2582-4.
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  We report on a novel zoom lens with no moving parts in the form of a switchable Galilean telescope. This zoom telescope consists of two flat liquid-crystal diffractive lenses with apertures of 10mm that can each take on the focal lengths of -50 and +100cm, with a spacing of 50cm and, hence, a zoom ratio of 4x. The lenses are driven using a low-voltage ac source with 1.6V and exhibit millisecond switching times. The spectral characteristic of this diffractive zoom system is evaluated for light sources of various bandwidths. Potential applications for this technology include a zoom lens with no moving parts for camera phones and medical imaging devices.
• DeHoog, E., & Schwiegerling, J. (2009). Fundus camera systems: A comparative analysis. Applied Optics, 48(2), 221-228.
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  PMID: 19137032;PMCID: PMC2845292;Abstract: Retinal photography requires the use of a complex optical system, called a fundus camera, capable of illuminating and imaging the retina simultaneously. The patent literature shows two design forms but does not provide the specifics necessary for a thorough analysis of the designs to be performed. We have constructed our own designs based on the patent literature in optical design software and compared them for illumination efficiency, image quality, ability to accommodate for patient refractive error, and manufacturing tolerances, a comparison lacking in the existing literature. © 2009 Optical Society of America.
• Marks, R., Mathine, D. L., Peyman, G., Schwiegerling, J., & Peyghambarian, N. (2009). Adjustable fluidic lenses for ophthalmic corrections. Optics Letters, 34(4), 515-517.
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  PMID: 19373359;PMCID: PMC2845295;Abstract: We report on two fluidic lenses that have been developed for ophthalmic applications. The lenses use a circular aperture to demonstrate optical powers between -20 and +20 D and a rectangular aperture to demonstrate astigmatism with values ranging from 0 to 8 D. Measurements of image quality were made with the fluidic lens using a model eye. Both lenses were variable and controllable by adjusting the fluid volume of the lens. To the best of our knowledge this is the first demonstration of a continuously variable lens for control of astigmatism. © 2009 Optical Society of America.
• Marks, R., Mathine, D. L., Peyman, G., Schwiegerling, J., & Peyghambarian, N. (2009). Adjustable fluidic lenses for ophthalmic corrections. Optics letters, 34(4), 515-7.
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  We report on two fluidic lenses that have been developed for ophthalmic applications. The lenses use a circular aperture to demonstrate optical powers between -20 and +20 D and a rectangular aperture to demonstrate astigmatism with values ranging from 0 to 8 D. Measurements of image quality were made with the fluidic lens using a model eye. Both lenses were variable and controllable by adjusting the fluid volume of the lens. To the best of our knowledge this is the first demonstration of a continuously variable lens for control of astigmatism.
• Marks, R., Mathine, D. L., Schwiegerling, J., Peyman, G., & Peyghambarian, N. (2009). Astigmatism and defocus wavefront correction via Zernike modes produced with fluidic lenses. Applied Optics, 48(19), 3580-3587.
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  PMID: 19571912;PMCID: PMC2846177;Abstract: Fluidic lenses have been developed for ophthalmic applications with continuously varying optical powers for second order Zernike modes. Continuously varying corrections for both myopic and hyperopic defocus have been demonstrated over a range of three diopters using a fluidic lens with a circular retaining aperture. Likewise, a six diopter range of astigmatism has been continuously corrected using fluidic lenses with rectangular apertures. Imaging results have been characterized using a model eye. © 2009 Optical Society of America.
• Marks, R., Mathine, D. L., Schwiegerling, J., Peyman, G., & Peyghambarian, N. (2009). Astigmatism and defocus wavefront correction via Zernike modes produced with fluidic lenses. Applied optics, 48(19), 3580-7.
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  Fluidic lenses have been developed for ophthalmic applications with continuously varying optical powers for second order Zernike modes. Continuously varying corrections for both myopic and hyperopic defocus have been demonstrated over a range of three diopters using a fluidic lens with a circular retaining aperture. Likewise, a six diopter range of astigmatism has been continuously corrected using fluidic lenses with rectangular apertures. Imaging results have been characterized using a model eye.
• Peng, W. u., DeHoog, E., & Schwiegerling, J. (2009). Systematic error of a large dynamic range aberrometer. Applied Optics, 48(32), 6376-6380.
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  PMID: 19904339;Abstract: Shack-Hartmann aberrometers are routinely used for measuring ocular aberrations. In one configuration, the intermediate images of the Shack-Hartmann spots formed by the lenslet array are relayed by an imaging lens onto a sensor. A systematic introduction of spherical aberration that is strongly related to the power error (defocus) of the incident wavefront is observed in this configuration. We found that the largest component of this error is induced by the pupil aberration of the imaging relay lens. Some simulations and experimental results are demonstrated. © 2009 Optical Society of America.
• Peng, W. u., Liu, S., Dehoog, E., & Schwiegerling, J. (2009). Systematic errors analysis for a large dynamic range aberrometer based on aberration theory. Applied Optics, 48(32), 6324-6331.
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  PMID: 19904333;Abstract: In Ref. [1], it was demonstrated that the significant systematic errors of a type of large dynamic range aberrometer are strongly related to the power error (defocus) in the input wavefront. In this paper, a generalized theoretical analysis based on vector aberration theory is presented, and local shift errors of the SH spot pattern as a function of the lenslet position and the local wavefront tilt over the corresponding lenslet are derived. Three special cases, a spherical wavefront, a crossed cylindrical wavefront, and a cylindrical wavefront, are analyzed and the possibly affected Zernike terms in the wavefront reconstruction are investigated. The simulation and experimental results are illustrated to verify the theoretical predictions. © 2009 Optical Society of America.
• Schwiegerling, J. (2009). Blue light-filtering intraocular lenses and scotopic sensitivity. Journal of Cataract and Refractive Surgery, 35(11), 2032-.
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  PMID: 19878847;
• Schwiegerling, J. (2009). Statistical generation of normal and post-refractive surgery wavefronts. Clinical and Experimental Optometry, 92(3), 223-226.
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  PMID: 19371266;Abstract: Background: Wavefront sensors provide detailed information regarding the aberration structure of large populations of patients. Knowledge of the statistical distribution of the aberrations has several applications, including the development of ophthalmic devices. The statistical distribution aids in defining the required performance range of the device. Another application would be customised schematic eye models that incorporate likely patterns of aberrations found in a given subject population. These models can then be used to find the statistical distribution of image quality metrics based on metrics such as MTF and retinal spot size. Methods: Myopic and post-refractive surgical patient populations were analysed to determine the statistical properties of their ocular aberrations. A matrix method is developed that can be used to generate aberration coefficients that are consistent with each population. Results: Generated wavefronts have statistical properties similar to the respective populations and incorporate the correlations between aberration coefficients. Conclusion: The matrix techniques illustrated here can be used to generate wavefronts that are consistent with various populations of interest to the ophthalmic community. Generation of wavefronts enables techniques such as Monte Carlo simulations to be performed that aid in the development of ophthalmic instrumentation and visual performance metrics. © 2009 Optometrists Association Australia.
• Schwiegerling, J., & Paleta-Toxqui, C. (2009). Minimal movement zoom lens. Applied Optics, 48(10), 1932-1935.
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  PMID: 19340148;Abstract: We make a novel telescope design using a pair of Alvarez lenses. Previous examples using these types of lenses were single elements used just to provide a change in power. Consequently, the location of the object and/or image plane must move. In this effort, we combine two elements to form a telescope. In this manner, we can fix the location of the object and image plane and simply change magnification. We describe the shapes of the Alvarez lenses used, as well as the advantages, the disadvantages, and the differences between a telescope using Alvarez lenses and a traditional telescope. © 2009 Optical Society of America.
• Schwiegerling, J., & Schwiegerling, J. T. (2009). Statistical generation of normal and post-refractive surgery wavefronts. Clinical & experimental optometry : journal of the Australian Optometrical Association, 92(3).
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  Wavefront sensors provide detailed information regarding the aberration structure of large populations of patients. Knowledge of the statistical distribution of the aberrations has several applications, including the development of ophthalmic devices. The statistical distribution aids in defining the required performance range of the device. Another application would be customised schematic eye models that incorporate likely patterns of aberrations found in a given subject population. These models can then be used to find the statistical distribution of image quality metrics based on metrics such as MTF and retinal spot size.
• Schwiegerling, J., DeHoog, E., & Schwiegerling, J. T. (2009). Fundus camera systems: a comparative analysis. Applied optics, 48(2).
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  Retinal photography requires the use of a complex optical system, called a fundus camera, capable of illuminating and imaging the retina simultaneously. The patent literature shows two design forms but does not provide the specifics necessary for a thorough analysis of the designs to be performed. We have constructed our own designs based on the patent literature in optical design software and compared them for illumination efficiency, image quality, ability to accommodate for patient refractive error, and manufacturing tolerances, a comparison lacking in the existing literature.
• Schwiegerling, J., DeHoog, E., Luo, H., Oka, K., Dereniak, E., & Schwiegerling, J. T. (2009). Snapshot polarimeter fundus camera. Applied optics, 48(9).
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  A snapshot imaging polarimeter utilizing Savart plates is integrated into a fundus camera for retinal imaging. Acquired retinal images can be processed to reconstruct Stokes vector images, giving insight into the polarization properties of the retina. Results for images from a normal healthy retina and retinas with pathology are examined and compared.
• Schwiegerling, J., Wu, P., DeHoog, E., & Schwiegerling, J. T. (2009). Systematic error of a large dynamic range aberrometer. Applied optics, 48(32).
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  Shack-Hartmann aberrometers are routinely used for measuring ocular aberrations. In one configuration, the intermediate images of the Shack-Hartmann spots formed by the lenslet array are relayed by an imaging lens onto a sensor. A systematic introduction of spherical aberration that is strongly related to the power error (defocus) of the incident wavefront is observed in this configuration. We found that the largest component of this error is induced by the pupil aberration of the imaging relay lens. Some simulations and experimental results are demonstrated.
• Schwiegerling, J., Wu, P., Liu, S., DeHoog, E., & Schwiegerling, J. T. (2009). Systematic errors analysis for a large dynamic range aberrometer based on aberration theory. Applied optics, 48(32).
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  In Ref. 1, it was demonstrated that the significant systematic errors of a type of large dynamic range aberrometer are strongly related to the power error (defocus) in the input wavefront. In this paper, a generalized theoretical analysis based on vector aberration theory is presented, and local shift errors of the SH spot pattern as a function of the lenslet position and the local wavefront tilt over the corresponding lenslet are derived. Three special cases, a spherical wavefront, a crossed cylindrical wavefront, and a cylindrical wavefront, are analyzed and the possibly affected Zernike terms in the wavefront reconstruction are investigated. The simulation and experimental results are illustrated to verify the theoretical predictions.
• Choi, J., & Schwiegerling, J. (2008). Optical performance measurement and night driving simulation of ReSTOR, ReZoom, and tecnis multifocal intraocular lenses in a model eye. Journal of Refractive Surgery, 24(3), 218-222.
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  PMID: 18416255;Abstract: PURPOSE: To measure the optical properties of multifocal intraocular lenses (IOLs) for different pupil sizes. METHODS: An artificial eye was fabricated that had both the average spherical aberration and chromatic aberration levels found in the human eye. This model eye contained a saline-filled wet cell into which various IOLs can be mounted. Pupil sizes of 3 and 6 mm were explored with the system. Using the model eye, the following IOLs were examined: Alcon ReSTOR apodized diffractive, AMO ReZoom zonal refractive, and Tecnis ZM900 full-aperture diffractive. The modulation transfer function (MTF) for the lenses was calculated. The model eye was also used as a portable device to photograph nighttime driving scenes. RESULTS: For 3-mm pupils, the apodized and full-aperture diffractive IOLs balance contrast between near and distance vision, whereas the zonal refractive IOL performs poorly for near vision. For 6-mm pupils, the apodized diffractive shifts performance from near vision to distance vision, whereas the zonal refractive and full-aperture diffractive IOLs continue to balance performance between distance and near. Subjectively, the night driving photographs showed much more stray light artifacts for the zonal refractive and the full-aperture and apodized diffractive IOLs. CONCLUSIONS: Under dark conditions, the shift of optical performance of the apodized diffractive lens towards distance vision reduces artifacts that appear under night driving conditions. These artifacts remain for the zonal refractive and full-aperture diffractive lenses.
• DeHoog, E., & Schwiegerling, J. (2008). Optimal parameters for retinal illumination and imaging in fundus cameras. Applied Optics, 47(36), 6769-6777.
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  PMID: 19104528;Abstract: A fundus camera is a complex optical system for imaging the retina of the eye. Designing a fundus camera requires the combination of an imaging system and an illumination system to share common optics. This combination of systems results in the need to find an optimal balance between imaging and illuminating the retina. We present a series of parameters and methods used to optimize the illumination system of a fundus camera while maintaining excellent image quality. © 2008 Optical Society of America.
• Jain, P., & Schwiegerling, J. (2008). RGB Shack-Hartmann wavefront sensor. Journal of Modern Optics, 55(4-5), 737-748.
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  Abstract: The Shack-Hartmann wavefront sensor is the most widely used instrument to measure the optical aberrations of the human eye. Traditional Shack-Hartmann wavefront sensors measure the ocular aberrations at a single wavelength, which is usually in the near infrared region of the spectrum. A modified Shack-Hartmann wavefront sensor that simultaneously measures aberrations at three visible wavelengths is discussed. The modified instrument provides a measurement of the longitudinal chromatic aberration of the eye in addition to the monochromatic aberrations provided by the conventional device. Human subjects testing results and the comparison of measured LCA with clinical values are presented.
• Schwiegerling, J., & Choi, J. (2008). Application of the polychromatic defocus transfer function to multifocal lenses. Journal of Refractive Surgery, 24(9), 965-969.
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  PMID: 19044242;Abstract: PURPOSE: To model the performance of multifocal lenses in polychromatic lighting. METHODS: The defocus transfer function (DTF) is a mathematical technique for illustrating the optical transfer function for all levels of defocus at a given wavelength. A polychromatic version of the DTF is developed that accounts for changes in cutoff frequency, reduction in diffraction efficiency, ocular chromatic aberration, and photoreceptor spectral sensitivity. The differences between the monochromatic and polychromatic DTF are illustrated with a diffractive multifocal intraocular lens. RESULTS: Polychromatic analysis shows an increase in depth of field of diffractive lenses relative to assessment at a single wavelength. CONCLUSIONS: The polychromatic DTF is a useful tool for analyzing presbyopia treatments under "white-light" viewing conditions and provides feedback to lens designers on anticipated performance.
• Schwiegerling, J., Choi, J., & Schwiegerling, J. T. (2008). Optical performance measurement and night driving simulation of ReSTOR, ReZoom, and Tecnis multifocal intraocular lenses in a model eye. Journal of refractive surgery (Thorofare, N.J. : 1995), 24(3).
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  To measure the optical properties of multifocal intraocular lenses (IOLs) for different pupil sizes.
• Schwiegerling, J., DeHoog, E., & Schwiegerling, J. T. (2008). Optimal parameters for retinal illumination and imaging in fundus cameras. Applied optics, 47(36).
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  A fundus camera is a complex optical system for imaging the retina of the eye. Designing a fundus camera requires the combination of an imaging system and an illumination system to share common optics. This combination of systems results in the need to find an optimal balance between imaging and illuminating the retina. We present a series of parameters and methods used to optimize the illumination system of a fundus camera while maintaining excellent image quality.
• Schwiegerling, J. (2007). Analysis of the optical performance of presbyopia treatments with the defocus transfer function. Journal of Refractive Surgery, 23(9), 965-971.
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  PMID: 18041255;Abstract: PURPOSE: A variety of techniques for treating presbyopia are available. However, these techniques are often disparate in the mechanisms used to cope with the lack of accommodation. Multizone-refractive, diffractive, and apodized intraocular lens technologies are currently being used. This article evaluates the optical performance of these markedly different technologies in a simple and comparable manner. METHODS: The Defocus Transfer Function is a mathematical technique for illustrating the Optical Transfer Function for all levels of defocus. By calculating the Defocus Transfer Function, the simulated performance of presbyopia correction technologies on distance, intermediate, and near vision, can be evaluated simultaneously. Simulations of an opaque annular ring, a zonal refractive lens, a full-aperture diffractive lens, and an apodized diffractive lens are analyzed at pupil sizes of 3, 4, and 6 mm with this technique. RESULTS: The opaque annulus begins to act like a Fresnel amplitude zone plate for small pupils. The diffractive lens technologies had sharp optical performance at two distinct foci with a shift in performance from balanced to distance-biased for the apodized diffractive lens. The zonal refractive lens exhibited a multifocal effect. However, the optical performance of this technology fell below that of the diffractive lenses. CONCLUSIONS: The Defocus Transfer Function is a useful tool for analyzing presbyopia treatments. Different strategies for creating simultaneous vision or extended depth of field are easily compared. It may also be possible to reverse this technique to create an ideal pupil function that meets a desired multifocal performance specification.
• Schwiegerling, J., & Schwiegerling, J. T. (2007). Analysis of the optical performance of presbyopia treatments with the defocus transfer function. Journal of refractive surgery (Thorofare, N.J. : 1995), 23(9).
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  A variety of techniques for treating presbyopia are available. However, these techniques are often disparate in the mechanisms used to cope with the lack of accommodation. Multizone-refractive, diffractive, and apodized intraocular lens technologies are currently being used. This article evaluates the optical performance of these markedly different technologies in a simple and comparable manner.
• Bagwell, B. E., Wick, D. V., & Schwiegerling, J. (2006). Multi-spectral foveated imaging system. IEEE Aerospace Conference Proceedings, 2006.
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  Abstract: The development of sensors that are smaller, lighter weight and require less bandwidth is critical for the success of space-based and airborne imaging systems. One solution to this problem is foveated imaging, wherein a liquid crystal spatial light modulator is used to selectively enhance resolution in a wide field-of-view imaging system. Selective enhancement decreases the bulk and complexity of the optical train, while simultaneously reducing data transmission and processing requirements. This enhancement is done modulo 2π, as such it is inherently a monochromatic correction. In this paper, we propose to overcome that limitation by introducing a switchable polarization interference filter, obtaining near diffraction limited performance over the instantaneous field-of-view (IFOV) at the wavelength(s) of interest.
• Bagwell, B. E., Wick, D. V., Batchko, R., Mansell, J. D., Martinez, T., Restaino, S. R., Payne, D. M., Harriman, J., Serati, S., Sharp, G., & Schwiegerling, J. (2006). Liquid crystal based active optics. Proceedings of SPIE - The International Society for Optical Engineering, 6289.
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  Abstract: Liquid crystal spatial light modulators, lenses, and bandpass filters are becoming increasingly capable as material and electronics development continues to improve device performance and reduce fabrication costs. These devices are being utilized in a number of imaging applications in order to improve the performance and flexibility of the system while simultaneously reducing the size and weight compared to a conventional lens. We will present recent progress at Sandia National Laboratories in developing foveated imaging, active optical (aka nonmechanical) zoom, and enhanced multispectral imaging systems using liquid crystal devices.
• Beverage, J. L., & Schwiegerling, J. (2006). A Shack-Hartmann-based autorefractor. Journal of Refractive Surgery, 22(9), 932-937.
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  PMID: 17124892;Abstract: PURPOSE: Autorefractors are typically based on either the optometer or the Scheiner principles, or a combination of the two techniques. These devices have dominated the market for objective assessment of refractive error for >30 years. The purpose of this investigation is to test a Shack-Hartmann-based system as an alternative to these systems. METHODS: Fourteen subjects with varying levels of refractive error were measured with a Topcon autorefractor and a Shack-Hartmann-based autorefractor. Fourier transform techniques were used to extract sphere, cylinder, and axis information from the Shack-Hartrnann images, avoiding the need for image processing. The deviation of the refractive error from a subjective refraction was used as a means of comparing the two devices. RESULTS: The two devices performed similarly on this group of subjects. The mean difference in refraction between the two devices was nearly zero, suggesting that the likelihood and magnitude of errors for the two devices are equivalent. CONCLUSIONS: The Shack-Hartmann-based autoretractor shows promise as an afternative to conventional optometer or Scheiner-based technologies. However, issues with extending the myopic range of the device still need to be resolved.
• Guoqiang, L. i., Mathine, D. L., Valley, P., Äyräs, P., Haddock, J. N., Giridhar, M. S., Williby, G., Schwiegerling, J., Meredith, G. R., Kippelen, B., Honkanen, S., & Peyghambarian, N. (2006). Switchable electro-optic diffractive lens with high efficiency for ophthalmic applications. Proceedings of the National Academy of Sciences of the United States of America, 103(16), 6100-6104.
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  PMID: 16597675;PMCID: PMC1458838;Abstract: Presbyopia is an age-related loss of accommodation of the human eye that manifests itself as inability to shift focus from distant to near objects. Assuming no refractive error, presbyopes have clear vision of distant objects; they require reading glasses for viewing near objects. Area-divided bifocal lenses are one example of a treatment for this problem. However, the field of view is limited in such eyeglasses, requiring the user to gaze down to accomplish near-vision tasks and in some cases causing dizziness and discomfort. Here, we report on previously undescribed switchable, flat, liquid-crystal diffractive lenses that can adaptively change their focusing power. The operation of these spectacle lenses is based on electrical control of the refractive index of a 5-μm-thick layer of nematic liquid crystal using a circular array of photolithographically defined transparent electrodes. It operates with high transmission, low voltage (
• Guoqiang, L. i., Mathine, D., Valley, P., Äyräs, P., Haddock, J., Giridhar, M., Schwiegerling, J., Meredith, G., Kippelen, B., Honkanen, S., & Peyghambarian, N. (2006). Switchable diffractive lens for vision correction. Optics and Photonics News, 17(12), 28-.
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  Abstract: New switchable, flat, thin liquid crystal diffractive lenses have been introduced that offer stringent requirements including high light efficiency, relatively large aperture, fast switching time, low driving voltage, and power-failure-safe configuration. Lenses with eight phase levels, 10 mm diameters, and focal length of 1m and 0.5m have been demonstrated at 555nm. The lens operate with high transmission, low voltage, fast response, a diffraction efficiency exceeding 90%, small aberrations, and a power-failure-safe configuration. Negative focusing powers can also be obtained with the same lenses by changing the sign of the slope of the applied voltages. These represent a significant advance in the state-of-the-art in liquid crystal diffractive lens for vision care and other applications and also have the potential of revolutionizing the field of presbyopia correction.
• Guoqiang, L. i., Valley, P., Ayräs, P., Haddock, J., Giridhar, M. S., Mathine, D., Schwiegerling, J., Meredith, G., Kippelen, B., Honkanen, S., & Peyghambarian, N. (2006). High-efficiency switchable diffractive lens. Proceedings of SPIE - The International Society for Optical Engineering, 6310.
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  Abstract: We demonstrate that, by using circular array of electrode pattern and applying multi-level phase modulation in each zone, a high-efficiency switchable electro-optic diffractive lens using liquid crystal as the active medium can be produced as a switchable eyewear. The lens is flat and the thickness of the liquid crystal is 5 μm. Two different designs are presented. In one design, all the patterned electrodes are distributed in one layer with a 1-μm gap between the electrodes. In the other design, the odd- and even-numbered electrodes are separately patterned in two layers without any lateral gaps between the electrodes. In both cases, vias are made for interconnection between the electrodes and the conductive wires. With the one-layer electrode design, both 1-diopter and 2-diopter 8-level lenses are demonstrated with an aperture of 10 mm. With the two-layer electrode design, a 2-diopter, 15-mm, 4-level lens is demonstrated. The diffraction efficiency of the 8-level lens can be higher than 90%. The ON- and OFF-state of the electrically controlled lens allow near- and distance-vision respectively for presbyopic eyes. The focusing power of the lens can be adjusted to be either positive or negative. The focusing power of the 8-level lens can be adjusted for near-, intermediate-, and distance vision. The lens is compact and easy to operate with fast response time, low voltages and low power dissipation. This is the first demonstration of the switchable lenses that almost meet the requirements for spectacle lens.
• Peyghambarian, N., Li, G., Mathine, D., Valley, P., Schwiegerling, J., Honkanen, S., Äyräs, P., Haddock, J. N., Malalahalli, G., & Kippelen, B. (2006). Electro-optic adaptive lens as a new eyewear. Molecular Crystals and Liquid Crystals, 454(1), 157/[559]-166/[568].
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  Abstract: Adaptive lens with the capability of changing the focusing power has important applications in 3D imaging, optical information processing, and ophthalmology. We demonstrate a switchable electroactive lens with very high diffraction efficiencies using a circular array of electrode pattern filled with liquid crystal as the active medium to be used as an adaptive eyewear. Electrically adjustable lens allows the focal length to be voltage controlled without bulky and inefficient mechanical movement. Binary Fresnel zone plates using liquid crystal as active material have been demonstrated for imaging applications, but the diffraction efficiency is low. The lens is flat and the thickness of the liquid crystal is 5 m. Diffraction efficiencies exceeding 90% has been achieved for an 8-level diffractive lens. The lens can be operated as both positive and negative lens. Design, modeling, fabrication, and characterization of the lens is presented. Using nematic liquid crystal, the lens is polarization dependent and two crossed lenses are integrated to form a complete lens. The ON- and OFF-state of the electrically controlled lens allow near- and distance-vision respectively for presbyopia eyes.
• Sarver, E. J., Schwiegerling, J., & Applegate, R. A. (2006). Extracting wavefront error from Shack-Hartmann images using spatial demodulation. Journal of Refractive Surgery, 22(9), 949-953.
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  PMID: 17124895;PMCID: PMC1851688;Abstract: PURPOSE: To determine whether the spatial demodulation processing of Shack-Hartmann images is suitable for extracting wavefront gradients for ocular wavefront sensors. METHODS: We developed a custom software program to implement the spatial demodulation technique. To test the algorithm's performance, we generated simulated spot images and obtained an eye examination image. We generated a collection of simulated aberrated spot images corresponding to: astigmatic wavefront (-5.00 -2.00 × 17), highly aberrated defocus (±20.00 diopters [D]), high-resolution defocus (-0.01 D), and third-order aberrations (trefoil and coma). The eye examination image and its measured Zernike coefficients were obtained from a Shack-Hartmann ocular aberrations system. We evaluated the output from the algorithm in terms of comparing the results to the known Zernike coefficients (for the simulated images) or the previously measured Zernike coefficients (for the eye examination image). RESULTS: The spatial demodulation algorithm was able to correctly recover the aberrations to better than 1/100 (0.01) D for the simulated spot images. The processing of the eye examination image yielded results within approximately 1/4 (0.25) D to the values provided by the Shack-Hartmann system. CONCLUSIONS: From the set of simulated images and the eye examination image used to test the spatial demodulation technique, it appears that the method is suitable for application in ocular wavefrant aberrations Shack-Hartmann systems. The method appears capable of accurately processing high levels of aberrations (±20.00 D) as well as providing high resolution as evidenced by finding the -0.01 D defocus. The method may be especially well suited for processing highly aberrated wavefronts.
• Schwiegerling, J. (2006). Blue-light-absorbing lenses and their effect on scotopic vision. Journal of Cataract and Refractive Surgery, 32(1), 141-144.
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  PMID: 16516793;Abstract: PURPOSE: To correct assumptions about material transmission and provide a more realistic assessment of the optical properties of intraocular lenses (IOLs) made from AcrySof Natural material (Alcon). SETTING: University of Arizona Department of Ophthalmology, Tucson, Arizona, USA. METHODS: The transmission characteristics of conventional and AcrySof Natural IOL materials immersed in a balanced salt solution were examined to determine the differences in scotopic vision. The removal of the crystalline lens during cataract surgery and its effect on scotopic vision were also analyzed. RESULTS: When only considering the IOL properties, the AcrySof Natural lens decreased light entering the eye under scotopic by 14.6%, much lower than previously reported. Furthermore, when removal of the crystalline lens was taken into consideration, the AcrySof Natural material actually increased the amount of light entering the eye by 52% under these same conditions. CONCLUSIONS: Previous discrepancies in the transmission characteristics of IOL materials have led to an underestimation of the performance of the AcrySof Natural material under scotopic conditions. Accounting for both transmission and the crystalline lens demonstrates an increase in light levels entering the eye with the AcrySof Natural material when compared to young phakic subjects. © 2006 ASCRS and ESCRS.
• Schwiegerling, J. (2006). Recent developments in pseudophakic dysphotopsia. Current Opinion in Ophthalmology, 17(1), 27-30.
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  PMID: 16436921;Abstract: Purpose of review: Photic phenomena associated with intraocular lenses can degrade visual performance following intraocular lens implantation. Postoperative dysphotopsia introduces glare, halos, starbursts and shadows in a small number of patients. Understanding the optical mechanisms behind the introduction of these artifacts can lead to improved lens design and a reduction in the deleterious effects of stray light. This review looks at the improvement efforts of recent years to illustrate the systematic hunt for lens problems. Recent findings: Improvements in edge designs have diminished the effects of positive dysphotopsia. However, negative dysphotopsia remains poorly understood and a variety of lens designs and materials can cause negative dysphotopsia. In other efforts, a testing procedure has been developed to improve understanding of the visual percept of a patient suffering dysphotopsia. This test should enlighten practitioners to the deficits their patients face and provide clues to the root causes of the problems. Summary: Intraocular lenses can introduce stray light artifacts into the eye. These artifacts manifest themselves as glare, halos, starbursts and shadows. While positive dysphotopsia (glare, halos and starbursts) has been largely attributed to edge effects of the implant, negative dysphotopsia remains somewhat mysterious and appears to be more related to the patient's anatomical structure than to specific lens designs or materials. © 2006 Lippincott Williams & Wilkins.
• Schwiegerling, J. (2006). Reply: Blue-blocking intraocular lenses and pseudophakic scotopic sensitivity. Journal of Cataract and Refractive Surgery, 32(9), 1404-1405.
• Schwiegerling, J., & Schwiegerling, J. T. (2006). Recent developments in pseudophakic dysphotopsia. Current opinion in ophthalmology, 17(1).
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  Photic phenomena associated with intraocular lenses can degrade visual performance following intraocular lens implantation. Postoperative dysphotopsia introduces glare, halos, starbursts and shadows in a small number of patients. Understanding the optical mechanisms behind the introduction of these artifacts can lead to improved lens design and a reduction in the deleterious effects of stray light. This review looks at the improvement efforts of recent years to illustrate the systematic hunt for lens problems.
• Andrews, J., Teare, S., Restaino, S., Wilcox, C., Wick, D., Xiao, H., & Schwiegerling, J. (2005). Dynamic aberration control testbed for the characterization of multiple wavefront sensors. Proceedings of SPIE - The International Society for Optical Engineering, 6018.
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  Abstract: An optical testbed has been developed for the comparative analysis of wavefront sensors based on a modified Mach Zender interferometer design. This system provides simultaneous measurements of the wavefront sensors on the same camera by using a common aberrator. The initial application for this testbed was to evaluate a Shack-Hartmann and Phase Diversity wavefront sensors referenced to a Mach-Zender interferometer. This testbed has the added benefit of being able to train the deformable mirror against the spatial light modulator and evaluate its ability to compensate the spatial light modulator. In the paper we present some results from the wavefront sensors along with preliminary results from the wavefront corrective elements in the optical testbed.
• Andrews, J., Teare, S., Restaino, S., Wilcox, C., Wick, D., Xiao, H., & Schwiegerling, J. (2005). Optical testbed for comparative analysis of wavefront sensors. Proceedings of SPIE - The International Society for Optical Engineering, 5892, 1-7.
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  Abstract: An optical testbed has been developed for the comparative analysis of wavefront sensors based on a modified Mach Zender interferometer design. This system provides simultaneous measurements of the wavefront sensors on the same camera by using a common aberrator. The initial application for this testbed was to evaluate a Shack-Hartmann and Phase Diversity wavefront sensors referenced to a Mach-Zender interferometer. In the current configuration of the testbed, aberrations are controlled using a liquid crystal spatial light modulator, and corrected using a deformable mirror. This testbed has the added benefit of being able to train the deformable mirror against the spatial light modulator and evaluate its ability to compensate the spatial light modulator. In the paper we present results from the wavefront sensors in the optical testbed.
• Schwiegerling, J. (2005). Modal reconstruction methods with zernike polynomials. Journal of Refractive Surgery, 21(5), S552-S557.
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  PMID: 16209460;Abstract: PURPOSE: To compare the advantages and disadvantages of different techniques for fitting Zemike polynomials to surfaces. METHODS: Two different methods, Orthogonal Projection and Gram-Schmidt orthogonalization, are compared in terms of speed and performance at fitting a complex object. RESULTS: Orthogonal Projection provides an extremely rapid fitting of a surface, but leaves residual high frequency noise. The Gram-Schmidt technique provides a more accurate fit of the original object, but consumes much more computing time. Orthogonal Projection, and its associated noise, may be tolerated in classifying corneal topography. CONCLUSIONS: Orthogonal Projection has a distinct advantage in calculation time over other methods for fitting surfaces. This advantage may be exploited in cases where accurate surface fitting is not necessary, but only general features need to be extracted for classification. If fit accuracy is needed, then slower fitting techniques, such as Gram-Schmidt, should be used.
• Schwiegerling, J. (2004). Gaussian weighting of ocular wave-front measurements. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 21(11), 2065-2072.
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  PMID: 15535364;Abstract: The measurement of ocular wave-front error gives insight into the optical performance of the eye and possibly a means for assessing visual performance. The visual system responds not only to the quality of the optical image formed on the retina but also to the processing that occurs in the retina and the brain. To develop a metric of visual performance based on wave-front error measurements, these latter processes must somehow be incorporated. In representing the wave-front error in terms of Zernike polynomials, it appears that terms with lower angular frequency have a greater deleterious effect on visual performance than higher- angular-frequency terms. A technique for weighting the pupil function of the eye with a Gaussian filter is demonstrated. It is further demonstrated that the variance of the Gaussian-weighted wave-front error is well correlated with visual performance. © 2004 Optical Society of America.
• Schwiegerling, J. (2004). Wavefront-Guided Lasik. Optics and Photonics News, 15(2), 26-29.
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  Abstract: The wavefront guided laser assisted in situ keratomileusis (LASIK) technique is discussed. In the technique aberration patterns are measured pre-operatively and a customized ablation pattern is generated. The monochromatic aberrations of the eyes are corrected, and a diffraction limited performance resulting in an acuity better than 20/10 is achieved. A summary of the clinical trials for the products offered by the three companies that have received an approval for the technology is also presented.
• Schwiegerling, J., & Schwiegerling, J. T. (2004). Gaussian weighting of ocular wave-front measurements. Journal of the Optical Society of America. A, Optics, image science, and vision, 21(11).
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  The measurement of ocular wave-front error gives insight into the optical performance of the eye and possibly a means for assessing visual performance. The visual system responds not only to the quality of the optical image formed on the retina but also to the processing that occurs in the retina and the brain. To develop a metric of visual performance based on wave-front error measurements, these latter processes must somehow be incorporated. In representing the wave-front error in terms of Zernike polynomials, it appears that terms with lower angular frequency have a greater deleterious effect on visual performance than higher-angular-frequency terms. A technique for weighting the pupil function of the eye with a Gaussian filter is demonstrated. It is further demonstrated that the variance of the Gaussian-weighted wave-front error is well correlated with visual performance.
• Straub, J., & Schwiegerling, J. (2003). Surgical and healing changes to ocular aberrations following refractive surgery. Proceedings of SPIE - The International Society for Optical Engineering, 4951, 139-149.
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  Abstract: The surgery and healing changes in manifest refraction, spherical aberration, and pupil diameter for a large number of subjects that underwent LASIK refractive surgery were analyzed. The surgery dramatically decreases refractive errors and the correction was maintained throughout the healing process. On the other hand, LASIK refractive surgery dramatically increases the amount of spherical aberration in the human eye. The results show that corrections of large aberration made with customized refractive surgery will be sustained through the healing process.
• Miller, J. M., Anwaruddin, R., Straub, J., & Schwiegerling, J. (2002). Higher order aberrations in normal, dilated, intraocular lens, and laser in situ keratomileusis corneas. Journal of Refractive Surgery, 18(5), S579-S583.
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  PMID: 12361161;Abstract: PURPOSE: To compare repeated measures of Zernike polynomial higher-order aberrations in 29 normal, 13 dilated normal, 11 intraocular lens (IOL), 11 laser in situ keratomileusis (LASIK), and one refractive keratectomy (RK)/IOL subject. METHODS: At least three Shack-Hartmann images were obtained from each subject, and higher order (uncorrectable by spectacles) Zernike representation was determined. For each subject, confidence intervals for each Zernike coefficient were determined as a function of pupil size. Significant (P
• Schwiegerling, J. (2002). LASIK and beyond. Optics and Photonics News, 13(1), 30-33.
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  Abstract: The applications of laser-assisted in situ keratomileuis - LASIK for reducing refractive error in the eye is discussed. In this process a device called microkeratome is used to shave a thin, hinged flap in the cornea. Pulses from an excimer laser operating at a wavelength of 193 nm are then delivered to this tissue to modify its shape.
• Schwiegerling, J. (2002). Scaling Zernike expansion coefficients to different pupil sizes. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 19(10), 1937-1945.
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  PMID: 12365613;Abstract: Recent developments in technologies to correct aberrations in the eye have fostered extensive research in wave-front sensing of the eye, resulting in many reports of Zernike expansions of wave-front errors of the eye. For different reports of Zernike expansions, to be compared, the same pupil diameter is required. Since no standard pupil size has been established for reporting these results, a technique for converting Zernike expansion coefficients from one pupil size to another is needed. This investigation derives relationships between the Zernike expansion coefficients for two different pupil sizes. © 2002 Optical Society of America.
• Schwiegerling, J., & Schwiegerling, J. T. (2002). Scaling Zernike expansion coefficients to different pupil sizes. Journal of the Optical Society of America. A, Optics, image science, and vision, 19(10).
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  Recent developments in technologies to correct aberrations in the eye have fostered extensive research in wave-front sensing of the eye, resulting in many reports of Zernike expansions of wave-front errors of the eye. For different reports of Zernike expansions, to be compared, the same pupil diameter is required. Since no standard pupil size has been established for reporting these results, a technique for converting Zernike expansion coefficients from one pupil size to another is needed. This investigation derives relationships between the Zernike expansion coefficients for two different pupil sizes.
• Schwiegerling, J., Snyder, R. W., & Lee, J. H. (2002). Wavefront and topography: Keratome-induced corneal changes demonstrate that both are needed for custom ablation. Journal of Refractive Surgery, 18(5), S584-S588.
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  PMID: 12361162;Abstract: PURPOSE: To examine the effects of laser in situ keratomileusis (LASIK) flap incision and healing on the shape of the cornea and the wavefront error of the eye. METHODS: Four weeks prior to bilateral LASIK, study subjects had a flap cut using a keratome in one eye. The fellow eye remained untouched as a control. Corneal topography and wavefront errors were measured at 1 day, 1, and 4 weeks after the flap was created. After 4 weeks, the flap was lifted and LASIK was performed. The control eye also had LASIK at this time. RESULTS: Differences in corneal shape and wavefront error consistent with a mild hyperopic shift were seen as a result of the keratome incision. CONCLUSION: Cutting the flap in LASIK causes subtle changes to corneal shape and the optics of the eye that may affect customized treatments. Additional work is needed to quantify these changes so that their effect can be incorporated into future treatments.
• Thibos, L. N., Applegate, R. A., Schwiegerling, J. T., & Webb, R. (2002). Standards for reporting the optical aberrations of eyes. Journal of Refractive Surgery, 18(5), S652-S660.
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  PMID: 12361175;Abstract: In response to a perceived need in the vision community, an OSA taskforce was formed at the 1999 topical meeting on vision science and its applications (VSIA-99) and charged with developing consensus recommendations on definitions, conventions, and standards for reporting of optical aberrations of human eyes. Progress reports were presented at the 1999 OSA annual meeting and at VSIA-2000 by the chairs of three taskforce subcommittees on (1) reference axes, (2) describing functions, and (3) model eyes.
• Miller, J. M., Schwiegerling, J., Leising-Hall, H., & Surachatkumtonekul, T. (2001). Detection of improper fixation in MTI photoscreening images. Journal of AAPOS, 5(1), 35-43.
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  PMID: 11182671;Abstract: Purpose: To determine the effect of fixation shift on photoscreening crescents, the ability of human interpreters to detect fixation shift, and the potential improvement by image processing. Methods: MTI photoscreening (Medical Technologies & Innovations, Inc, Lancaster, PA) images, measured at 11 positions of gaze, were obtained from 10 subjects (9 with refractive error warranting spectacle correction). Photographs were taken with subjects fixating at 20, 15, 10, and 5 cm to the left and the right of the camera fixation target (1 m distant); 5 cm above and below the camera fixation target; and on-axis. Photographs were inspected by 11 experienced raters, who indicated if the subject appeared to be looking directly at the camera. The photographs were digitized, enlarged, contrast enhanced, and measured by 3 raters. For each photograph, distance from the corneal light reflex to the nasal limbus was measured and a measure of asymmetry computed. Results: Raters could reliably detect off-axis fixation greater than 10 cm away from the intended fixation target. Raters correctly identified on-axis subject viewing 73% of the time. Crescents became larger when the fixation shifted off-axis for both the myopic and hyperopic subjects. Image analysis correctly classified 10 of 10 on-axis measurements and 34 of 39 off-axis measurements. Conclusion: Direct inspection of photoscreening images by trained raters can result in the failure to detect small but relevant errors of fixation. These fixation shifts can cause crescents to become larger than expected, resulting in false-positive classification. Image analysis offers a potential improvement in the detection of off-axis fixation in MTI photoscreening images.
• MacRae, S. M., Schwiegerling, J., & Snyder, R. (2000). Customized corneal ion and super vision. Journal of Refractive Surgery, 16(2 SUPPL.), S230-S235.
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  Abstract: PURPOSE: To review the early development of new technologies that are becoming available through customized corneal ablation techniques. METHODS: The authors describe the early development of two diagnostic methods to perform customized corneal ablation as well as a variety of new treatment modalities in development. RESULTS and CONCLUSION: Results using the wavefront sensors indicate that these techniques have the potential to be more sensitive than traditional refraction and keratometry. Subtle defects such as coma and spherical aberration can be detected and treated. A whole series of new technologies are being incorporated to treat patients with customized corneal ablation.
• Schwiegerling, J. (2000). Theoretical limits to visual performance. Survey of Ophthalmology, 45(2), 139-146.
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  PMID: 11033040;Abstract: Wavefront sensors and scanning laser technology are enabling the correction of the aberrations of the eye. The effects of aberrations on visual performance are reviewed, and the theoretical limit of visual performance is predicted to understand the ultimate endpoint of these new technologies. A schematic eye model that incorporates diffraction, chromatic aberration, photopic response, the Stiles-Crawford effect, and pupil size is ray-traced to determine its limiting optical properties. These properties are compared to the detection requirements of the retina and brain to determine the theoretical limit of foveal vision. The theoretical limits on foveal vision are found to be between 20/12 and 20/5, depending on pupil diameter. It is concluded that emerging refractive surgery technologies may provide substantial increases in visual performance. Copyright (C) 2000 Elsevier Science Inc.
• Schwiegerling, J., & Snyder, R. W. (2000). Corneal ablation patterns to correct for spherical aberration in photorefractive keratectomy. Journal of Cataract and Refractive Surgery, 26(2), 214-221.
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  PMID: 10683788;Abstract: Purpose: To determine the spherical aberration introduced by photorefractive keratectomy (PRK) and customize ablation patterns to compensate for this aberration and improve post-PRK visual performance. Setting: Department of Ophthalmology, University of Arizona, Tucson, Arizona, USA. Methods: Presurgical and postsurgical corneal topography of 16 patients who had PRK with the Summit OmniMed laser were obtained. The data were applied to a schematic eye model, and exact ray tracing was used to determine the introduction of spherical aberration from the procedure. Optimization routines were used to determine the ideal ablation pattern. Results: The magnitude of the spherical aberration introduced into the eyes after PRK increased with the level of attempted correction. The theoretical ideal ablation pattern requires additional flattening of the ablation periphery to avoid the introduction of spherical aberration. Conclusions: Current PRK ablations introduce spherical aberration into the eye. Modifying the existing ablation algorithms to compensate for spherical aberration may boost postoperative visual performance. (C) 2000 ASCRS and ESCRS.
• Schwiegerling, J., & Snyder, R. W. (2000). Eye movement during laser in situ keratomileusis. Journal of Cataract and Refractive Surgery, 26(3), 345-351.
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  PMID: 10713227;Abstract: Purpose: To measure eye motion in patients having laser in situ keratomileusis (LASIK) using a video technique and determine centration and variance of the eye position during surgery. Setting: Laser refractive surgery center. Methods: The procedure was videotaped in 5 consecutive eyes having LASIK performed by a single surgeon with the VISX Star S2 excimer laser. Following surgery, video images of the eyes were digitized and stored in a computer for processing. Digitized images were obtained at a rate of 25 images per second during the laser procedure. The pupil margin and a visual landmark, such as a scleral blood vessel, were identified in the initial image of each eye. Custom software was used to track the location of the landmark and the pupil center in subsequent images. Results: Three of the 5 eyes were well centered on average. The remaining 2 eyes were decentered inferiorly by approximately 0.25 mm. The standard deviation in all eyes was approximately 0.10 mm. Conclusions: With these techniques, the position of the entrance pupil center relative to the excimer laser axis could be determined. Although the system is not fast enough to be used during surgery, it does allow quantification of centration and intraoperative motion after surgery. (C) 2000 ASCRS and ESCRS.
• Snyder, R. W., Siekert, R. W., Schwiegerling, J., Donnenfeld, E., & Thompson, P. (2000). Acular as a single agent for use as an antimiotic and anti-inflammatory in cataract surgery. Journal of Cataract and Refractive Surgery, 26(8), 1225-1227.
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  PMID: 11008052;Abstract: Purpose: To assess the safety and effectiveness of ketorolac tromethamine 0.5% (Acular®) as a cost-efficient single agent to prevent intraoperative miosis and postoperative inflammation in cataract surgery. Methods: Both eyes of 26 patients were randomized to receive Acular preoperatively and postoperatively or flurbiprofen sodium (Ocufen®) preoperatively and prednisolone acetate 1% (Pred Forte®) postoperatively. Time scheduled between procedures was from 2 weeks to 1 month. Pupil dilation was measured preoperatively, intraoperatively, and at the end of surgery. Cell and flare were measured 1 day, 1 week, and 1 month postoperatively. Results: A comparison of the Acular and the Ocufen/Pred Forte groups (n=22) showed no statistically significant differences in dilation (preoperative versus postpostoperative) or cell and flare postoperatively. Conclusion: Using Acular as a single agent was as effective as the combination of preoperative Ocufen and postoperative Pred Forte in preventing intraoperative miosis and postoperative inflammation in cataract surgery. The use of Acular as a single agent could save the expense of using separate anti-inflammatory and antimiotic preparations preoperatively and postoperatively, enhancing convenience for the surgeon and surgical facility. (C) 2000 ASCRS and ESCRS.
• Thibos, L. N., Applegate, R. A., Schwiegerling, J. T., & Webb, R. (2000). Report from the VSIA taskforce on standards for reporting optical aberrations of the eye. Journal of Refractive Surgery, 16(5), S654-S655.
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  PMID: 11019893;
• MacRae, S., Schwiegerling, J., & Snyder, R. W. (1999). Customized and low spherical aberration corneal ablation design. Journal of Refractive Surgery, 15(2 SUPPL.), S246-S248.
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  PMID: 10202734;Abstract: PURPOSE: The purpose of this study was to use the Arizona Eye Model to help guide customization of corneal excimer ablation and reduce spherical aberration. METHODS: Myopic eyes were treated with the Nidek EC-5000 excimer laser with a 5.5-mm diameter optic ablation zone and a 7.0-mm diameter transition ablation zone. We analyzed preoperative and postoperative corneal topographies using height mapping. From this data, refractive error profiles and maps were constructed using the Arizona Eye Model. The first group of patients had refractions between -2.00 and -5.00 D. Data was obtained by subtracting postoperative topography from preoperative topography. We then plotted the ideal ablation pattern if no additional spherical aberration was introduced when compared to preoperative topographies. RESULTS: We found that in the central 4 mm, the ablation pattern was highly acceptable, with negligible spherical aberration. As the ablation moved out toward 6 mm, there was increasing spherical aberration. Newer ablation designs require more flattening in the midperiphery of the cornea. These flatter peripheral designs require more blending in the periphery and larger transition zones. CONCLUSION: The use of computerized corneal topography in eye modeling is helpful in designing new ablation patterns to reduce optical and spherical aberration. Ablation zone design is critical to maximizing optical and biologic tolerance.
• Schwiegerling, J., & Snyder, R. W. (1999). Visual performance modeling following RK, PRK, and LASIK demonstrates the need for improved treatment algorithms. Ophthalmic Practice, 17(2), 66-70.
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  Abstract: Refractive surgery has emerged as a means of correcting refractive error. A variety of techniques have been developed for modifying the dioptric power of the cornea, with varying degrees of success. Perhaps the most widespread techniques in use today are radial keratotomy (RK), photorefractive keratectomy (PRK), and laser in situ keratomileusis (LASIK). The goal of these procedures has been to reduce spherical and cylindrical refractive error. However, little attention has been devoted to visual distortions introduced by these procedures. Postoperative patients often complain about glare, halos, and difficulty seeing low contrast objects in dim lighting, even though they have 6/6 (20/20) vision. A fundamental understanding of the assessment of visual performance and the mechanisms behind these visual problems is useful for proper patient education and optimizing surgical techniques to alleviate the problems.
• Schwiegerling, J., & Snyder, R. W. (1998). Custom photorefractive keratectomy ablations for the correction of spherical and cylindrical refractive error and higher-order aberration. Journal of the Optical Society of America A: Optics and Image Science, and Vision, 15(9), 2572-2579.
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  PMID: 9729870;Abstract: Photorefractive keratectomy is an evolving refractive procedure for correcting myopia, hyperopia, and astigmatism. Earlier descriptions of the patterns required for this surgery are based on paraxial optics. In this investigation the required pattern is generalized to account for spherical refractive error (defocus), axial astigmatism of arbitrary orientation, and fourth-order aberrations of the eye. The patterns described in this study can be used to customize photorefractive keratectomy and to provide corrections that account for aberration content as well as paraxial values. Furthermore, a description of the pattern along the boundary of the optical zone is given, which may prove useful in designing blending zones. An example of the use of these techniques is given for a schematic eye model. © 1998 Optical Society of America.
• Schwiegerling, J. (1997). Cone dimensions in keratoconus using Zernike polynomials. Optometry and Vision Science, 74(11), 963-969.
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  PMID: 9403892;Abstract: Purpose. To determine the physical dimensions and location of the cone in keratoconic corneas from videokeratoscopic height data. Methods. Corneal height data from keratoconus patients are obtained with a commercial videokeratoscope and decomposed into the set of orthogonal Zernike polynomials. The low-order Zernike terms are removed from the height data to expose the cone. The location of the peak of the cone and the cone's height and lateral dimensions are measured from the residual height data. This technique is compared to previous dioptric power-based methods of locating the cone. Results. The corneal protrusion due to keratoconus takes on a variety of shapes and locations. These dimensions are easily measured with the Zernike decomposition technique and provide more detailed and accurate information regarding the cone than dioptric power data. Conclusions. The proposed method for quantifying cone dimensions and locale in keratoconic corneas provides practical and detailed information which may be useful in tracking the progression of the disease, contact lens fitting, and surgical planning.
• Schwiegerling, J., & Greivenkamp, J. E. (1997). Using corneal height maps and polynomial decomposition to determine corneal aberrations. Optometry and Vision Science, 74(11), 906-916.
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  PMID: 9403887;Abstract: Purpose. To review the use of corneal videokeratoscopic height data, elaborate on the advantages and disadvantages of such data, describe techniques for overcoming the limitations of height data, and demonstrate its use in quantifying the optical properties and aberrations of the cornea. Methods. The steep sag of the cornea hides fine variations in corneal height that arise naturally or due to disease or surgery. The dynamic range, or ratio of the overall sag to the feature height, is the primary limitation of videokeratoscopic height data. Techniques for removing single or multiple reference surfaces are described in detail, and applications of the methodology to wavefront and raytracing analysis of corneal aberrations arising from radial keratotomy (RK), photorefractive keratectomy (PRK), and keratoconus are described. Results. Removing a single reference surface from the raw corneal height data begins to reveal subtle variations in corneal height. However, expansion of surface height data into a complete set of basis functions provides a sophisticated method for extracting high-order corneal variations. Choosing an orthogonal basis set provides a robust least- squares fit and forms unique expansions of the surface. The resulting coefficients are uncorrelated and form a simple measure of the optical quality. Conclusion. Videokeratoscopic height data are useful for analyzing and quantifying corneal deformity arising from disease or refractive surgery and they provide a sophisticated alternative or complement to dioptric power maps.
• Schwiegerling, J., & Schwiegerling, J. T. (1997). Cone dimensions in keratoconus using Zernike polynomials. Optometry and vision science : official publication of the American Academy of Optometry, 74(11).
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  To determine the physical dimensions and location of the cone in keratoconic corneas from videokeratoscopic height data.
• Greivenkamp, J. E., Mellinger, M. D., Snyder, R. W., Schwiegerling, J. T., Lowman, A. E., & Miller, J. M. (1996). Comparison of three videokeratoscopes in measurement of toric test surfaces. Journal of Refractive Surgery, 12(2), 229-239.
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  PMID: 8653525;Abstract: PURPOSE: We compared the accuracy of the Computed Anatomy TMS-1 (1.41), the EyeSys Laboratories Corneal Analysis System (2.1), and the Visioptic EH- 270 (3.0) videokeratoscopes in measuring toric surfaces. These non- rotationally symmetric aspheric surfaces served as models of corneal astigmatism. METHODS: Precision diamond-turned toric surfaces modeling 0.00 diopter (D) to 7.00 D of astigmatism were fabricated. A three-dimensional contact profiler was developed to calibrate the aspheric surfaces. Videokeratoscopic data taken at 'best focus' were compared to the theoretical shape to quantify device measurement errors. RESULTS: The Computed Anatomy system measurement accuracy shows no statistically significant correlation between measurement error and surface toricity (r20.96, p
• Hall, H. L., Miller, J. M., Greivenkamp, J. E., & Schwiegerling, J. T. (1996). Prediction of identification difficulty of sloan letters based on spatial frequency content. Investigative Ophthalmology and Visual Science, 37(3), S1076.
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  Abstract: Purpose. Standardization of visual acuity optotypes is crucial to the accurate measurement of visual acuity. The currently used charts have been developed based on subjective measures and clinical calibration. Sloan (AJO 1959) observed that there is a difference in rate of identification of each letter at threshold visual acuity. We propose a set of quantitative measures to predict the identification difficulty of visual acuity optotypes based on their spatial frequency content that we expect to aid in the development of future optotypes to test for specific deficiencies. Methods. The magnitude of the two-dimensional Fourier transform of the Sloan letters (in order of ease of recognition) ZNHRVKDCOS was calculated. Each spectrum was integrated over 45 degree wedges oriented at 90, 45, 0 and -45 degrees between the spatial frequencies of 1.5 and 30 cycles/degree. The following quantitative measures were chosen: the ratio of the integrated volume under the Fourier transform in the 90 and 0 degree wedges (horizontal vs. vertical information); the ratio of the 45 to the -45 degree wedges (symmetry in the diagonal directions); the ratio of the sum of the 90 and 0 degree wedges to the sum of the 45 and -45 degree (vertical and horizontal vs. oblique information); and the circular symmetry of the transform (curves in the object). Results. Multiple linear regression on these 4 parameters yielded a prediction for the reported difficulty of identification with r2 = 0.91 and p = 0.008 and ease of detection order of ZNHVRDKSCO. Conclusions. Analysis of the spatial frequency content of optotypes is useful in predicting their detectability at visual acuity threshold.
• Schwiegerling, J. T., Greivenkamp, J. E., & Miller, J. M. (1996). Keratoconus detection from videokeratoscopic height data. Investigative Ophthalmology and Visual Science, 37(3), S558.
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  Abstract: Purpose. Current videokeratoscopic-based keratoconus detection schemes primarily look for asymmetries in the dioptric power of the cornea. Recently, Hubbe and Foulks (Ophthalmology. 1994;101:1745-1748) have shown that poor fixation of normal patients can produce similar dioptric power asymmetries resulting in a false detection of keratoconus. A technique to detect keratoconus in the presence of corneal misalignment is investigated. Methods. Corneal height data for 61 myopic and 17 keratoconus patients is obtained with a TMS-1 videokeratoscope (Computed Anatomy, New York, NY). A 6 mm diameter zone from each set of height data is expanded into the orthogonal set of Zernike polynomials. Expansion terms representing a planar tilt fit the misalignment of the cornea, while the higher-order coma-like terms fit the cone. The magnitude of the first coma-like Zernike term and the spherical equivalent power obtained from the expansion coefficients are compared between the myopic and keratoconus groups. Results. The net "coma" coefficient is 0.0076 ± 0.0046 for the keratoconus group and is 0.0013 ± 0.0008 for the myopic group. These values differ significantly (p
• Schwiegerling, J., & Greivenkamp, J. E. (1996). Keratoconus detection based on videokeratoscopic height data. Optometry and Vision Science, 73(12), 721-728.
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  PMID: 9002087;Abstract: Purpose. To develop a videokeratoscopic-based keratoconus detection scheme that avoids the ambiguity of dioptric power definitions and videokeratoscope design. Methods. Corneal height data obtained with a commercial videokoratoscope are decomposed into the set of orthogonal Zernike polynomials. Expansion coefficients of a 'normal' group and a keratoconus group are compared to find significant differences. Elevated Zernike terms are used to detect the disease in these populations. The performance of this detection scheme is compared to other videokeratoscopic keratoconus indices. Results. Two low-order Zernike polynomial terms are identified as being elevated in keratoconus patients and combined to form a new detection index. This index performed at least as well as keratoconus detection schemes based on the inferior-superior (I-S) value, the steepest radial axes (SRAX), and the Surface Asymmetry Index (SAI) for the samples studied. Conclusion. The proposed Zernike scheme offers a potentially viable algorithm for detecting keratoconus that avoids the ambiguities of dioptric power definitions and is independent of videokeratoscope design.
• Schwiegerling, J., Greivenkamp, J. E., Miller, J. M., Snyder, R. W., & Palmer, M. L. (1996). Optical modeling of radial keratotomy incision patterns. American Journal of Ophthalmology, 122(6), 808-817.
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  PMID: 8956635;Abstract: PURPOSE: To determine the optical effects of higher-order corneal shape variations resulting from radial keratotomy. METHODS: Videokeratoscopic height data were obtained postoperatively from several patients who had undergone radial keratotomy. For each of clear central zone sizes 3.00 mm, 4.00 mm, and 4.75 mm, two patients were chosen randomly from the larger study group. Data obtained 2 weeks postoperatively from these six patients were decomposed into the Zernike polynomials, and the low-order expansion terms were removed to disclose corneal height variations (the radial keratotomy artifact). The artifact was applied to a schematic eye model, and exact ray- tracing was used to evaluate visual performance, which was defined as a function of pupil diameter, optical zone (central clear zone) size, and radial keratotomy artifact centration. RESULTS: The radial keratotomy artifact degrades visual performance at midspatial frequencies more than it does at high spatial frequencies. This effect is most pronounced for smaller optical zones and for a pupil diameter of 4 min. Visual performance remains nearly constant for small decentration (0.5 mm or less) of the radial keratotomy optical zone from the corneal apex. CONCLUSIONS: Residual refractive error, corneal asphericity, and the radial keratotomy artifact all affect visual performance after radial keratotomy. Isolated effects of the radial keratotomy artifact degrade visual performance, with the level of degradation dependent on pupil size, optical zone size, and centration of the procedure. More research is necessary to combine the radial keratotomy artifact with changes in corneal asphericity and to further quantify the optical effects of radial keratotomy.
• Greivenkamp, J. E., Schwiegerling, J., Miller, J. M., & Mellinger, M. D. (1995). Visual acuity modeling using optical raytracing of schematic eyes. American Journal of Ophthalmology, 120(2), 227-240.
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  PMID: 7639307;Abstract: PURPOSE: We developed a methodology to predict changes in visual performance that result from changes in the optical properties of the eye. METHODS: Exact raytracing of schematic eyes was used to calculate the point spread function and the modulation transfer function of the visual system. The Stiles-Crawford effect, photopic response, diffraction, and the retinal contrast sensitivity are included in the model. Visual acuity was predicted by examining the modulation of the resultant retinal image of a bar target and by determining when the modulation falls below a threshold value. Visual acuity was predicted for refractive errors ranging from 0 to 5 diopters and for pupil diameters ranging from 0.5 to 8 mm. RESULTS: Visual acuity predictions were compared to clinically found Snellen visual acuities and were found to be highly correlated (r2 = .909). CONCLUSIONS: This modeling technique shows promise as a means of evaluating clinical and surgical procedures before undertaking clinical trials.
• Schwiegerling, J., Greivenkamp, J. E., & Miller, J. M. (1995). Representation of videokeratoscopic height data with Zernike polynomials.. Journal of the Optical Society of America. A, Optics, image science, and vision, 12(10), 2105-2113.
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  PMID: 7500201;Abstract: Videokeratoscopic data are generally displayed as a color-coded map of corneal refractive power, corneal curvature, or surface height. Although the merits of the refractive power and curvature methods have been extensively debated, the display of corneal surface height demands further investigation. A significant drawback to viewing corneal surface height is that the spherical and cylindrical components of the cornea obscure small variations in the surface. To overcome this drawback, a methodology for decomposing corneal height data into a unique set of Zernike polynomials is presented. Repeatedly removing the low-order Zernike terms reveals the hidden height variations. Examples of the decomposition-and-display technique are shown for cases of astigmatism, keratoconus, and radial keratotomy.

Proceedings Publications

• Schwiegerling, J. T. (2018, August). Optimizing trefoil phase plates design for color wavefront coding. In SPIE Optics and Photonics, 10745, 1074515.
• Schwiegerling, J. T. (2018, August). Using light fields to simulate the performance of optical systems. In SPIE Optics and Phototomics, 10743, 1074308.
• Schwiegerling, J. T. (2018, May). Image simulation using decomposition of the point spread function. In SPIE Optical System Design, 10690, 1069006.
• Amirsolaimani, B., Peyghambarian, N. N., Schwiegerling, J. T., Bablumyan, A., Savidis, N., & Peyman, G. (2017, August). An automatic holographic adaptive phoropter. In SPIE Nanoscience and engineering 2017, 10352, 1035208.
• Schwiegerling, J. T. (2017, August). Linear decomposition of the optical transfer function for annular pupils. In SPIE Optics & Photonics, 10375, 103750F.
• Schwiegerling, J. T. (2017, August). Review of Zernike polynomials and their use in describing the impact of misalignment in optical systems. In SPIE Optics & Photonics, 10377, 103770D.
• Schwiegerling, J. T. (2017, June). Optical transfer function expansion of quadratic pupils. In International Optical Design Conference, 10590, 1059005.
• Schwiegerling, J. T. (2014, August). History of the Shack Hartmann wavefront sensor and its impact in ophthalmic optics. In SPIE Optics & Photonics.
• Schwiegerling, J. T. (2014, August). Plenoptic camera image simulation for reconstruction algorithm verification. In SPIE Optics & Photonics.

Presentations

• Schwiegerling, J. T. (2017, February). Binocular Combination of Multifocal IOLs. Wavefront & Presbyopic Refractive Corrections. San Jose, CA: Wavefront Congress.
• Schwiegerling, J. T. (2017, May). Realistic Three-Dimensional Scene Visualization Through Presbyopia Treatment Modalities. ARVO Annual Meeting. Baltimore, MD: Association for Research in Vision and Ophthalmology.
• Schwiegerling, J. T. (2017, October). Computer Simulations. Presbyopia 2017. Lisbon, Portugal: International Society of Presbyopia.

Poster Presentations

• Schwiegerling, J. T. (2017, October). Realistic Scenes Through Different Presbyopia Treatment Modalities. American Academy of Optometry Annual Meeting. Chicago: American Academy of Optometry.
• Harvey, E. M., Miller, J. M., Schwiegerling, J. T., Sherrill, D. L., Messer, D. H., & Twelker, J. D. (2012, May). Longitudinal Change in Corneal Astigmatism in Tohono O'odham Infants and Toddlers. Annual Meeting of Association for Research in Vision and Ophthalmology. Ft. Lauderdale, FL: Association for Research in Vision and Ophthalmology.
• Miller, J. M., Schwiegerling, J. T., Harvey, E. M., Sherrill, D. L., Messer, D. H., Twelker, J. D., Miller, J. M., Schwiegerling, J. T., Harvey, E. M., Sherrill, D. L., Messer, D. H., & Twelker, J. D. (2012, May). Data Reduction Strategies for Aberration Measurements in Tohono O'odham Infants and Children. Annual Meeting of Association for Research in Vision and Ophthalmology. Ft. Lauderdale, FL: Association for Research in Vision and Ophthalmology.

Others

• Schwiegerling, J. T. (2015, January). Plenoptic Imaging. McGraw-Hill Yearbook of Science and Technology.
• Das, K. K., Stover, J. C., Schwiegerling, J., & Karakelle, M. (2013, May). Technique for measuring forward light scatter in intraocular lenses. Journal of cataract and refractive surgery.
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  To develop a technique for measuring the forward light scattering of intraocular lenses (IOLs).
• Schwiegerling, J. T. (2013, Aug). Eye axes and their relevance to alignment of corneal refractive procedures. Journal of refractive surgery (Thorofare, N.J. : 1995).
• Harvey, E. M., Miller, J. M., Schwiegerling, J., Clifford-Donaldson, C. E., Green, T. K., Messer, D. H., & Dobson, V. (2011, Aug). Accuracy and validity of IK4 handheld video keratometer measurements in children. Journal of AAPOS : the official publication of the American Association for Pediatric Ophthalmology and Strabismus / American Association for Pediatric Ophthalmology and Strabismus.
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  The infant keratometer (IK4) is a custom handheld instrument that was designed specifically to allow measurement of corneal astigmatism in infants as young as 6 months of age. In this study, accuracy of IK4 measurements with the use of standard toric surfaces was within 0.25 D. Validity measurements obtained in 860 children aged 3-7 years demonstrated slightly greater astigmatism measurements in the IK4 than in the Retinomax K+. Measurement success was 98% when the IK4 was used. The IK4 may prove to be clinically useful for screening children as young as 3 years of age at high risk for corneal astigmatism.
• Schwiegerling, J. (2009, Nov). Blue light-filtering intraocular lenses and scotopic sensitivity. Journal of cataract and refractive surgery.