Date of Award

Fall 1983

Document Type


Degree Name

Master of Science (MS)


Ocean & Earth Sciences



Committee Director

Donald R. Johnson

Committee Member

Geore Ofelt

Committee Member

Ronald Johnson

Call Number for Print

Special Collections LD4331.O35R55


The objective of this study has been to develop an hypothesis explaining comparable aerial and underwater visual acuity of the bottlenose dolphin, Tursiops truncatus. This objective was accomplished by integrating the findings of other dolphin researchers working in the fields of comparative psychology, histology and ophthalmology. Their combined results enabled the formulation of a schematic dolphin eye. It is proposed that a dolphin lens, similar to the spherical lens of teleost fish with a rigid core of uniformly high refractive index and a margin of radially decreasing refractive index, could function as a bifocal lens and compensate for the eye's air-water transitions. Limited by the iris and oblique viewing directions in air, light would be focused by the cornea and lens margin onto a retinal area of densely packed photoreceptors capable of high visual resolution. In water, the cornea becomes optically insignificant and light from more axial viewing directions would be focused by the lens margin and core onto the same area of the retina. The behavioral findings indicate that the dolphin has evolved a passive optical system with a fixed best focus at infinity in air and between one and two meters in water. The dolphin eye is highly adapted to the oceanic environment in many respects: 1.) its streamlined, hydrodynamic shape, 2.) its great sensitivity to light through a large light-gathering pupil, a light reflecting tapetum, and a densely-populated, highly-summated retinal mosaic, J.) its greater sensitivity to the blue-green part of the spectrum, predominant in ocean water and 4.) its ability through the unique use of a bifocal lens, to focus in air and in water.


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