Raptors lack lower-field myopia

The presence of lower-field myopia (described in chickens, pigeons, quail and amphibians) allows these animals to keep the ground in focus while performing other visual tasks. A relationship has also been reported between the eye height and the degree of myopia observed. All of the animals reported in the literature to date are ground-foraging species. Using infrared neutralizing video retinoscopy and static photoretinoscopy we found a lower-field myopia to be absent in the barn owl (Tyto alba), Swainson's hawk (Buteo swainsonii), Cooper's hawk (Accipiter cooperi) and American kestrel (Falco sparverius). These findings suggest that the presence or absence of a lower-field myopia is a function of the visual ecology of the animal.