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Eyes see above and below water surface: four-eyed fish

Split eyes of the four-eyed fish allow it to see above and below the surface of the water simultaneously due to varying thickness in the lens.

"Native to Caribbean lagoons, Anableps anableps is commonly known as the four-eyed fish because its two eyes are split by horizontal partitions into two halves, each of which has its own iris and retina. This unique optical construction lets the fish swim at the surface of the water, with the upper half of each eye scanning the air for predatory fish-eating birds, and the lower half peering down below the surface, in search of small fish to feed on…Despite each eye being partitioned, there is only one oval-shaped lens per eye. Because vision through water requires a thicker lens than vision through air, the fish's eye is ingeniously adapted to fulfill two purposes, with the lower portion of each eye's lens (through which the fish sees underwater) thicker than the upper portion (through which the fish sees in air)." (Shuker 2001:12-13)
About the inspiring organism
Anableps anableps (Linnaeus, 1758)
Common names: Foureyed fish, Four-eyes, Largescale foureyes, Star gazer, Striped foureyed fish

Learn more at
Some organism data provided by: FishBase
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

IUCN Red List Status: Unknown

Bioinspired products and application ideas

Application Ideas: Treatments for cataracts. Lens designers can use this technique to develop optics for multiple media applications.

Industrial Sector(s) interested in this strategy: Medical

Shuker, KPN. 2001. The Hidden Powers of Animals: Uncovering the Secrets of Nature. London: Marshall Editions Ltd. 240 p.
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