Lee Russell McDowell (Vitamins in Animal Nutrition, on the web) has a summary of congenital defects caused by vitamin A deficiency in a variety of domestic animals. These are mostly mammals but also chicken and trout. In swine, congenital defects include both missing eyes and a large eye on one side and a small eye on the other side of the head.
IMO, the above bears consideration as a possible cause of eye and other abnormalities in snakes, particularly the species that eat eggs in the wild.
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