The Effects of Lens Grin Profiles on Phakometric Measurements

The in vivo dimensions and shape of the posterior crystalline lens surface in eyes are often calculated based on information taken from the image of that surface as viewed through the lens and the cornea. It is therefore necessary to choose a schematic eye model that successfully describes the optical properties of the interior of the lens in order to accurately determine the dimensions of its posterior surface. For simplicity the schematic eye models often assume that the refractive index of the lens is constant, although it is known to have a gradient of refractive index1. Evaluation of the resulting errors in calculations of the posterior lens surface dimensions have not previously been published. It will be shown that the gradient can have a profound effect on the image of the posterior lens surface of the lens in the Cichlid fish. The purpose of this paper is to investigate the effects of simplistic models on the calculations of the position, radius of curvature, and shape of the posterior lens surface in humans.