THE EYE OF THE DOMESTICATED SHEEP WITH IMPLICATIONS FOR VISION

The eyes of eighteen female sheep (Ovis aries) were refracted and deta ils of interocular distance, pupil size, shape and fundus presence rec orded. The sheep eyes generally possessed very low hyperopia with litt le astigmatism, such physiological optics being expected to produce a well focused retinal image for objects in the middle and long distance . No evidence was found for accommodation which would have produced a well focused ocular image for near objects. A further 10 sheep had the ir monocular and binocular visual fields measured. The estimated visua l field suggests the existence of at least binocular vision, if not th e presence of stereopsis. Given the lack of accommodation and a wide i nter-ocular distance, it is likely that some degree of stereopsis exis ts in the animal's middle and long distance vision, but is absent in n ear vision. These findings support those taken from the animal's neuro physiology and observations of its visually guided behaviour.