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  1. Ivan R Schwab
  1. University of California, Davis, Department of Ophthalmology, 4860 “Y” Street, Suite 2400, Sacramento, CA 95817, USA;

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    A diving, piscivorous bird faces some very special challenges that demand evolutionary creativity. A hunting vertebrate that pursues and captures prey under water must reckon with the loss of corneal refractive power since the cornea has approximately the same index of refraction as water. Hence, such hunters must rely upon lenticular accommodation for the entire dioptric power of the eye under water. But birds face an additional twist compared with predatorial fish. A bird must approximate emmetropia when airborne because its cornea will have refractive power in air as it will have a different index of refraction compared to air. Cormorants and their kin are a model for the successful solution to these problems. Most fish, on the other hand, never face air as a medium and consequently never use their cornea as a refractive surface. The Australian darter (Anhinga melanogaster), also known as one of the snakebirds (Anhingidae), seen on the cover is very closely related to cormorants, and allied to pelicans. Snakebirds are …

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