Abstract

We measured the mechanical properties of excised chicken eyes to test the possibility of a role of the intraocular pressure for corneal accommodation. It was found that the full range of corneal accommodation (~8 diopters) can be produced by small changes (~4 Torr) in intraocular pressure. We measured the speed of natural accommodation in the intact chick and found it to be ~10 times faster than human accommodation (50-80 diopters/s vs 4-6 diopters/s). A calculation of the aqueous outflow necessary to produce such a fast response in corneal accommodation showed that a model based solely on pressure changes is insufficient. Furthermore, we examined the off-axis refractive state in normal chicks both at rest and during accommodation. It was found that the refractive state is constant across the horizontal meridian but is more myopic in the lower visual field in most but not all individuals. During accommodation, the relative difference in refractive state is preserved in the different sectors of the visual field: accommodation is radially symmetrical.

© 1988 Optical Society of America