Polychromatic modelling of the human eye containing a GRIN lens

Abstract

The ingenuity and complexity of the human eye have attracted the interest of many researchers. In this thesis, we take a closer look at the polychromatic nature of the human eye, with special attention paid to the gradient refractive index (GRIN) nature of the human crystalline lens. The first chapter begins by providing an introduction into eye modelling; both schematically and physically, and finishes with information on the chromatic aberrations of the human eye. The focus of the second and third chapters is modelling chromatic aberration of the eye under various conditions. We first look at the change in longitudinal chromatic aberration (LCA) with ageing and the influence of different GRIN distributions on the transverse chromatic aberration (TCA) of the eye. The effect of choosing different dispersion profiles for the GRIN lens is also investigated, as well as the change in LCA with accommodation. Chapter three considers the built-in GRIN distribution of Zemax and this is used to extend our modelling capabilities. The LCA and TCA across the field are compared to experimental studies and the impact of tilting and decentering the GRIN lens on the TCA is also investigated. Finally, an analytical method to optimise the GRIN distribution and dispersion is shown. The method is then used to create a personalised eye model. The fourth chapter of the thesis begins by looking at contact lens correction for a personalised eye model. A method is then given for determining the deformable mirror shape of an open-loop, non-pupil conjugated adaptive optics system, which is capable of simulating a contact lens. The quality of the simulation is assessed in both the monochromatic and polychromatic case. The fifth chapter presents an opto-mechanical artificial eye that can be used for examining multi-wavelength ophthalmic instruments. Standard off-the-shelf lenses and a refractive index matching fluid were used in the creation of the artificial eye. A Hartmann-Shack aberrometer operating at three distinct wavelengths was used in the initial testing. Following this, off-axis chromatic aberrations were analysed by imaging through the artificial eye at two discrete wavelengths.