Visual Acuity Modeling Using Optical Raytracing of Schematic Eyes

We developed a methodology to predict changes in visual performance that result from changes in the optical properties of the eye. 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. Visual acuity predictions were compared to clinically found Snellen visual acuities and were found to be highly correlated (r2 = .909). This modeling technique shows promise as a means of evaluating clinical and surgical procedures before undertaking clinical trials.