Animals differ in visual acuity. Insects are short-sighted whereas a kestrel can spot a mouse from 1.5 km up. Hawks can spot prey 8 times further away than human beings can. The range of distances that animals can focus on is measured in dioptres. A child's range is about 14 dioptres, though an old person's is about 1 dioptre.
Many creatures have poor accommodation or none.
A dog copes with 1 dioptre. However, diving birds have 50 dioptres - the greatest of all animals. The position of the eyes on the head also varies amongst animals. Eye position controls the extent of the field of view when the head is stationary, and also the possibility and extent of binocular vision. When the eyes are on either side of the head, the view is almost panoramic, but there is a loss of stereoscopic depth perception.