Birds can move their eyes a bit, to extend their range of vision, but do not have the extensive ability of some reptiles to rotate the eyes. There are a number of diseases which can affect the eye, such as cataracts, conjuntivitis and absesses. Because birds rely so heavily on their eyesight, any problems should be treated immediately. Although the anatomy of the avian eye is similar to that of mammals, a few reptilian characteristics remain. These reptilian characteristics are the pectin structure within the globe of the eye and the scleratic ring of bony plates - scleral ossicles that support the shape of the globe.
Birds have enormous eyes relative to their body size and the keenest vision of all vertebrates.
The shape of avian eyes may be flat, globose, or tubular and varies according to the type of bird. The postion of the avian eye varies according to the shape of the skull. Pigeons, doves and parrots have narrow skulls with laterally placed eyes. Birds of prey, such as raptors, have broader skulls with more frontally positioned eyes. Laterally positioned eyes provide a large field of vision but a small binocular vision.