Corneal transmittance evaluation through different numerical and geometrical approximations

Abstract

Corneal analysis is usually done under two main considerations. First one consists of ignoring the second surface of the element, thus considering the cornea as a single diopter which isolates water from an aqueous medium with an equivalent keratometric index. Second approach consists of considering exact ray tracing and obtaining dot impact maps. Alternatively, differences of optical paths are measured over ray trajectories and thus the transmittance function is calculated. Main problems that may produce such approximations are that the second corneal surface is not taken into account, thus the model has not biological correspondence. From the second approach, ray distribution at the output plane is not uniformly sampled and rearrangement of emerging rays is needed. In this work we analyze the validity of both approximations by comparing those models with a realistic cornea. We propose a solution to overcome resampling at the output plane. We also propose several approximations over the optical path evaluation that may simplify calculation complexity. We will show that minimizing absolute differences in the optical path evaluation is not a good metrics to obtaining the best fitting corneal model.