Photon Trajectory in the Human Cornea
  In this article, we follow the trajectory of a photon in the human cornea. Prior to experimental evidence of the cornea's gradient refractive index (GRIN) nature, schematic eye models used a constant or average as the corneal refractive index. A few recent models respect the intra-corneal GRIN, but are based on the paraxial approximation, and thereby have limited validity in peripheral visual field analysis and non-paraxial photon tracking. Here, we introduce the Trajectron algorithm. It uses a closed form solution of the ray equation of constant axial GRIN media, and evaluates over piece-wise constant GRIN. Using Trajectron, we present the first quantitative demonstration of non-paraxial intra-corneal light-bending phenomena. This demonstration has significant implications in the development of refractive surgery algorithms. 
Stephen G. Odaibo
physics.optics q-bio.TO