CWhatUC: Software tools for predicting, visualizing and simulating corneal visual acuity.

摘要

The cornea is the transparent tissue covering the front of the eye, and performs about two-thirds of the refraction, or bending of light into the eye. Thus, subtle variations in its shape significantly affect a patient's visual acuity. Clinicians need to know the shape and refractive contribution of the cornea for several reasons: corneal refractive surgery, contact lens fitting and diagnosis of eye conditions. Instruments that measure the cornea's topography are called corneal topographers (CTs), and they have recently become a quite common tool for clinicians. These devices typically shine rings of light onto the cornea and capture the reflection pattern with a video camera. The raw data is extracted from the CT and a spline surface representation is constructed from these reflection patterns. All of our visualization and analysis is performed on these corneal surface representations.; In this work, we present CWhatUC, a set of software tools for the prediction, visualization and simulation of corneal visual acuity.; Prediction. We present a new method of representing visual acuity by measuring the wavefront aberration, using principles from both ray and wave optics. 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). 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 the indices we studied, including our own.; Visualization. Our proposed scientific visualizations can be clustered into two classes: corneal representations and retinal representations. Corneal representations are meant to reveal how well the cornea focuses parallel light onto the fovea of the eye by providing a pseudo-colored display of various error metrics. Retinal representations simulate how parallel incoming rays of light fall onto the retina, revealing aberrations and glare to the clinician.; We generated analytical models of common corneal shapes (with and without degenerative corneal conditions) and gathered a representative set of corneas from patients. We then rendered and analyzed all our visualizations against all of the corneas to illustrate how each representation contributes to the understanding of visual acuity.; Simulation. By measuring the light distribution of the cornea to a single point source of light, we capture the ""impulse response"" (in circuit terms) of the patient's visual system. We then convolve this with a scene to derive a very good first approximation of what the patient actually sees. We show demonstrations on a standard eye chart as well as a typical outdoor scene.; Only in recent years has the accurate reconstruction of the corneal shape been possible. With over half a million Americans a year choosing to undergo elective laser refractive eye surgery, the availability of accurate and revealing visualizations of corneal shape and acuity is crucial. CWhatUC represents a significant contribution to the tools available to clinicians, and to the emerging collaborative fields of computer graphics and vision science.