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Proceedings Paper

Bottlenose dolphin iris asymmetries enhance aerial and underwater vision
Author(s): Andre Rivamonte
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Paper Abstract

When the iris of the Bottlenose dolphin (Tursiops truncatus) contracts it constrains the path of light that can focus onto the two areas of the retina having a finer retinal mosaic. Under high ambient light conditions the operculum of the iris shields the lens and forms in the process two asymmetrically shaped, sized and positioned slit pupils. Tracing rays of light in the reverse direction through the pupils from the retinal regions associated with higher resolution confirm behaviorally observed preferred aerial and underwater viewing directions. In the forward and downward viewing direction, the larger temporal pupil admits light that is focused by the weakly refractive margin of a bifocal lens onto the temporal area centralis compensating for the addition of the optically strong front surface of the cornea in air. A schematic dolphin eye model incorporating a bifocal lens offers an explanation for a dolphin's comparable visual acuities in air and water for both high and low ambient light conditions. Comparison of methods for curve fitting psychometric ogive functions to behavioral visual acuity and spectral sensitivity data are discussed.

Paper Details

Date Published: 24 February 2009
PDF: 9 pages
Proc. SPIE 7163, Ophthalmic Technologies XIX, 716321 (24 February 2009); doi: 10.1117/12.804433
Show Author Affiliations
Andre Rivamonte, U.S. Army TMDE Activity (United States)

Published in SPIE Proceedings Vol. 7163:
Ophthalmic Technologies XIX
Fabrice Manns; Per G. Söderberg; Arthur Ho, Editor(s)

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