Abstract

Specializations were found in the cornea, ciliary body, lens, retina and optic nerve of the Tursiops eye. Light and interference contrast microscopy disclosed cornea thickness nearly 2 x human. Zonular insertions on the lens capsule are more complex than in human, but specific stains disclosed no significant accommodative musculature in the area of the ciliary body. Golgi stain disclosed both "rod" and "cone" receptor types in the retinal outer layer. Complex specializations of the amacrine cells provide "feedback" pathways across the plexiform layers. Most unusual are giant ganglion cells and their giant axons as seen in optic nerve cross section. These provide for unusually rapid communication between the eye and brain. This research was supported by National Science Foundation grant BNS 75-20147-AOI.

Notes

General comparison of dolphin's eye versus the terrestrial eye:

The dolphin eye is larger and has a larger cornea.

Angle of eye - has a fragile attachment of the ciliary body to the cornea.

Position of optic nerve - light coming into the eye directly through the center of the pupil falls
directly on the optic nerve rather than to the side as in the human. Thus, the dolphin likely cannot
see objects which are directly in front of the cornea.

Fundic vessels - similar to the cat.

Retina

• dolphins have rods and cones which suggest color vision.

• giant ganglion cells and giant axons are present. 

• multipolar cells exist in the fiber layer of the retina.

• two extra feedback loops exist in the retina, consisting of amacrine cell extensions and ganglion cells with processes which communicate.