Bottlenose dolphin iris asymmetries enhance aerial and underwater vision

Andre Rivamonte

doi:10.1117/12.804433

23 February 2009 Bottlenose dolphin iris asymmetries enhance aerial and underwater vision

Andre Rivamonte

Proceedings Volume 7163, Ophthalmic Technologies XIX; 716321 (2009) https://doi.org/10.1117/12.804433
Event: SPIE BiOS, 2009, San Jose, California, United States

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.

Citation Download Citation

Andre Rivamonte "Bottlenose dolphin iris asymmetries enhance aerial and underwater vision", Proc. SPIE 7163, Ophthalmic Technologies XIX, 716321 (23 February 2009); https://doi.org/10.1117/12.804433

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KEYWORDS

Iris

Visualization

Eye

Eye models

Cornea

Visual process modeling

Water

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