Kevin Baker

How keratoconus influences optical performance of the eye

Using a statistical description of keratoconus (KC) topography, schematic eye models of various KC conditions are constructed to study their optical influence on visual performance. The cone shape, protruding height and extent, and distance from the visual zone are independently investigated with the three-dimensional optical eye-modeling and ray-tracing techniques. The subsequent spherical equivalent (SE), cylinder, together with residual high-order ocular aberrations, are examined and related to each separated variable. The results show that myopic nature of SE is greatly dominated by the location of the cone. The cylinder is determined by the cone shape when the cone is inside the visual zone. It is dominated by the cone location when the cone is away from visual axis. The least myopic meridian always falls on the cone direction, and the high-order aberrations strongly relate to the cone dimension. This study investigates KC cone effect on optical quality and provides comprehension of clinical observations.

Simulation of realistic retinoscopic measurement

Realistic simulation of ophthalmic measurements on normal and diseased eyes is presented. We use clinical data of ametropic and keratoconus patients to construct anatomically accurate three-dimensional eye models and simulate the measurement of a streak retinoscope with all the optical elements. The results show the clinical observations including the anomalous motion in high myopia and the scissors reflex in keratoconus. The demonstrated technique can be applied to other ophthalmic instruments and to other and more extensively abnormal eye conditions. It provides promising features for medical training and for evaluating and developing ocular instruments.

Simulation of keratoconus observation in photorefraction

In the recent years, keratoconus (KC) has increasingly gained attention due to its treatment options and to the popularity of keratorefractive surgery. This paper investigates the potential of identification of KC using photorefraction (PR), an optical technique that is similar to objective retinoscopy and is commonly used for large-scale ocular screening. Using personalized eye models of both KC and pre-LASIK patients, computer simulations were performed to achieve visualization of this ophthalmic measurement. The simulations are validated by comparing results to two sets of experimental measurements. These PR images show distinguishable differences between KC eyes and eyes that are either normal or ametropic. The simulation technique with personalized modeling can be extended to other ophthalmic instrument developments. It makes possible investigation with the least number of real human subjects. The application is also of great interest in medical training.