A physiological model to measure optical and biophysical changes during avian accommodation

Abstract

A model was developed to directly measure optical and biophysical changes to the intact crystalline lens during ciliary nerve-induced accommodation. Lenticular optics during accommodation was analysed as a function of chicken age and i nametropic chicken eyes. Biophysical changes to the anterior segment of accommodating ametropic chicken eyes were assessed using the ultrasound biomicroscope. Resting state lenticular focal lengths increased as a function of age, presumably in association with growth rate of the eyes. The amount of lenticular accommodation decreased as a function of age . The optical quality in lenses from hatchlings was poor, regardless of accommodative state, suggesting that the lens was not fully developed. In general, spherical aberration was greater with accommodation for all age groups. Lenticular focal lengths were shorter and accommodation-associated changes in focal length were smaller for form-deprived myopic eyes compared to their controls. Induction of hyperopia with +15 D spectacle lenses resulted in attenuated, but opposite effects, with lenticular focal lengths longer and accommodative changes slightly greater for treated eyes than for their controls. Lenticular spherical aberration increased with accommodation in both form-deprived and lens-treated birds, but induction of ametropia had no effect on lenticular spherical aberration in general. Accommodation was associated with a decrease in anterior chamber depth and a bulging of the lens. Changes related to induction of myopia were subtle, while changes to hyperopic eyes were often undetectable, limited by the level of resolution of the biomicroscope.