OPTICS OF THE HARBOR PORPOISE EYE IN WATER

A two-dimensional ray-tracing model for the harbor porpoise eye is con structed from new measurements, mainly on two enucleated eyes, and fro m data found in the literature. Model calculations show that the cryst alline lens has too much refractive power to focus light on the retina . The cornea has a high refractive index and acts as a diverging lens of considerable refractive power. The cornea corrects the eye to near emmetropia for axial and temporal (caudal) directions of view. The eye is approximately 5-D myopic for nasal (frontal) directions of view. T he iris serves a dual role as a stop: the iris determines the shapes o f bundles of light that enter the lens and the iris blocks light that leaves the lens anterior to its equator.