Magnitude and rate of accommodation in diving and nondiving birds.

Accommodation was measured in a variety of waterfowl by projecting parallel low power helium-neon laser beams through the pupils of excised eyes placed in saline. The posterior globe was removed, allowing the beams, refracted only by the lens, to focus well behind the eye. Electrical stimulation of the ciliary muscle results in accommodative movement of the focal point toward the eye. Study of video recordings show that diving ducks (Mergus cucullatus and Bucephala clangala) can accommodate the 70-80 D needed to focus light on the retina when the eye is in water. Diving and nondiving species are compared in amount and rate of accommodation.