CWhatUC: a visual acuity simulator

Garcia, Daniel D.; Barsky, Brian A.; Klein, Stanley A.

doi:10.1117/12.309444

Cited by 8 publications

(3 citation statements)

References 12 publications

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“…Our model of the cornea is the same one used in our earlier work; 15 we again ignore the contribution of the lens and consider the cornea to be a uniform material with index of refraction (n) of 1.3375.…”

Section: Wavefront Coherence Areamentioning

confidence: 99%

“…Next, we determine where the light for that point will focus using Snell's law and Coddington's equations. 16,17 However, instead of calculating the focus from the mean of the principle refractive curvatures as we did in our earlier work, 15 here we use the maximum. We will discuss the rationale in the next section when we describe the cylinder correction.…”

Section: Wavefront Coherence Areamentioning

confidence: 99%

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Wavefront coherence area for predicting visual acuity of post-PRK and post-PARK refractive surgery patients

et al. 1999

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Many current corneal topography instruments (called videokeratographs) provide an "acuity index" based on corneal smoothness to analyze expected visual acuity. However, post-refractive surgery patients often exhibit better acuity than is predicted by such indices. One reason for this is that visual acuity may not necessarily be determined by overall corneal smoothness but rather by having some part of the cornea able to focus light coherently onto the fovea.We present a new method of representing visual acuity by measuring the wavefront aberration, using principles from both ray and wave optics. For each point P on the cornea, we measure the size of the associated coherence area whose optical path length (OPL), from a reference plane to P's focus, is within a certain tolerance of the OPL for P.We measured the topographies and vision of 62 eyes of patients who had undergone the corneal refractive surgery procedures of photorefractive keratectomy (PRK) and photorefractive astigmatic keratectomy (PARK). In addition to high contrast visual acuity, our vision tests included low contrast and low luminance to test the contribution of the PRK transition zone. We found our metric for visual acuity to be better than all other metrics at predicting the acuity of low contrast and low luminance. However, high contrast visual acuity was poorly predicted by all of the indices we studied, including our own.The indices provided by current videokeratographs sometimes fail for corneas whose shape differs from simple ellipsoidal models. This is the case with post-PRK and post-PARK refractive surgery patients. Our alternative representation that displays the coherence area of the wavefront has considerable advantages, and promises to be a better predictor of low contrast and low luminance visual acuity than current shape measures.

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Section: Wavefront Coherence Areamentioning

confidence: 99%

Section: Wavefront Coherence Areamentioning

confidence: 99%

Wavefront coherence area for predicting visual acuity of post-PRK and post-PARK refractive surgery patients

et al. 1999

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“…[44][45][46] Others carried out investigations using RRT based on measured corneal topography data. [47][48][49][50] Sarver et al also used corneal topography data and are principally capable of calculating optical components with their Visual Optics Lab* program. 51 Only few authors did RRT calculations including a gradient-index model of the human crystalline lens.…”

Section: Introductionmentioning

confidence: 99%

The Individual Virtual Eye: a Computer Model for Advanced Intraocular Lens Calculation

Einighammer

Oltrup

Bende

et al. 2009

Journal of Optometry

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PURPOSE:To describe the individual virtual eye, a computer model of a human eye with respect to its optical properties. It is based on measurements of an individual person and one of its major application is calculating intraocular lenses (IOLs) for cataract surgery. METHODS: The model is constructed from an eye's geometry, including axial length and topographic measurements of the anterior corneal surface. All optical components of a pseudophakic eye are modeled with computer scientific methods. A spline-based interpolation method efficiently includes data from corneal topographic measurements. The geometrical optical properties, such as the wavefront aberration, are simulated with real ray-tracing using Snell's law. Optical components can be calculated using computer scientific optimization procedures. The geometry of customized aspheric IOLs was calculated for 32 eyes and the resulting wavefront aberration was investigated. RESULTS: The more complex the calculated IOL is, the lower the residual wavefront error is. Spherical IOLs are only able to correct for the defocus, while toric IOLs also eliminate astigmatism. Spherical aberration is additionally reduced by aspheric and toric aspheric IOLs. The efficient implementation of time-critical numerical ray-tracing and optimization procedures allows for short calculation times, which may lead to a practicable method integrated in some device. CONCLUSIONS: The individual virtual eye allows for simulations and calculations regarding geometrical optics for individual persons. This leads to clinical applications like IOL calculation, with the potential to overcome the limitations of those current calculation methods that are based on paraxial optics, exemplary shown by calculating customized aspheric IOLs. (J Optom 2009;2:70-82 ©2009 Spanish Council of Optometry) KEY WORDS: real ray-tracing; Snell's law; corneal topography; wavefront aberration; intraocular lens calculation. RESUMEN OBJETIVO:Describir el ojo virtual individualizado, que es un modelo computacional de ojo humano con respecto a sus propiedades ópticas. Está basado en las medidas realizadas en cada persona, de manera individual. Una de sus principales aplicaciones es el cálculo de lentes intraoculares (LIO) para cirugía de cataratas. MÉTODOS:El modelo está construido a partir de datos de geometría ocular; en particular, la longitud axial y las medidas topográficas de la cara anterior de la córnea. Todos los componentes ópticos de un ojo pseudofáquico se modelan por medio de métodos computacionales científicos. El método de interpolación por splines permite incluir de manera eficiente los datos obtenidos en las medidas de topografía corneal. Las propiedades relacionadas con la óptica geométrica, como el patrón de aberración del frente de onda, se obtienen a partir de la simulación de un trazado de rayos reales, el cual emplea la ley de Snell. Los componentes ópticos se pueden calcular empleando procedimientos computacionales de optimización. Para 32 ojos distintos, se calculó la geometría de la c...

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12.1: Invited Paper: An Overview of Vision Realistic Rendering and Vision Correcting Displays

Barsky

2015

Symp Digest of Tech Papers

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Vision-realistic rendering is the computer generation of synthetic images that incorporate the characteristics of a par-ticular individual's entire optical system. Specifically, we simulate the scanned foveal image from wavefront data of actual human subjects.The concept of a vision correcting display involves digitally modifying the content of a display using measurements of the optical aberrations of the viewer's eye so that the display can be seen in sharp focus by the user without requiring the use of eyeglasses or contact lenses. Given the measurements of the optical aberrations of a user's eye, a vision correcting display will present a transformed image that when viewed by this individual will appear in sharp focus. Vision correction could be provided in some cases where spectacles are ineffective.

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CWhatUC: a visual acuity simulator

Cited by 8 publications

References 12 publications

Wavefront coherence area for predicting visual acuity of post-PRK and post-PARK refractive surgery patients

Wavefront coherence area for predicting visual acuity of post-PRK and post-PARK refractive surgery patients

The Individual Virtual Eye: a Computer Model for Advanced Intraocular Lens Calculation

12.1: Invited Paper: An Overview of Vision Realistic Rendering and Vision Correcting Displays

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