Wavefront guided corneal refractive surgeries, as well as implants and procedures to restore near-vision in presbyopic patients, require a knowledge of the optical, biometric and imaging properties of the lens. The optical properties of the human crystalline lens are determined by its shape and its refractive index gradient. These properties change with accommodation, which is the eye's ability to focus on near objects by changing the shape of the crystalline lens. The general goal of this study is to better understand the relationship between the refractive index gradient, the shape, specifically curvature and asphericity, of the human crystalline lens and its imaging properties, including paraxial optics as well as third and higher order aberrations. The working hypothesis is that when the shape of the lens changes during accommodation, there is a resulting change in both the asphericity and refractive index gradient that helps maintain the imaging quality produced by the lens. To demonstrate this hypothesis optical instrumentation will be developed to measure the shape, power and aberrations of ex vivo lenses during simulated accommodation in a lens stretching device developed in Dr. Parel's laboratory at Bascom Palmer Eye Institute. The results will be used to develop a higher-order dynamic optical model of the lens during accommodation.
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