A two-dimensional model simulating the pupil image in eccentric photorefraction

Abstract

Eccentric photorefraction and Purkinje image analyses of video can be used to estimate refractive state and eye position simultaneously (Schaeffel, Wilhelm, & Zrenner, 1993). They are used in screening and visual development studies (Choi et al., 2000). They are also helpful in understanding atypical development, but little is known about the effect of a number of variables (e.g. the impact of spectacle power and vertex distance). A two-dimensional model was built in Zemax to simulate eccentric photorefraction using sequential ray tracing. The two sub-models were: a forward version with appropriate light sources to create the retinal image and a backward version to create the camera image using the retinal image as the source (Chen, Tan, & Lewis, 2003). The slope of the luminance distribution across the pupil image was plotted against refractive state (±15D) and trial lens power (±8D) for a number of conditions. As shown previously (Roorda, Campbell, & Bobier, 1997), the results demonstrated slope saturation for significant refractive errors (>+4 & <−6D) and significant effects of pupil size. Refractive correction resulted in slope changes of up to 40% due to image magnification effects.

Meeting abstract presented at the 2016 OSA Fall Vision Meeting