ABSTRACT
The horse has the largest eye of any land mammal. The lateral globe placement and horizontal ovoid pupil allow a total visual field of 350°. Both eyes are used to look at a distant object until it comes within 1.0–1.3 metres, which forces the horse to turn the head and look with only one eye. The eyes of horses have a number of unique anatomical differences when compared with those of the dog and cat. These include a complete bony orbit, which gives added protection to the eye, and well-developed extraocular muscles, which make manipulation of the eyelids and globe challenging. A neuro-ophthalmic examination should be completed in the horse prior to sedation and/or nerve blocks. The palpebral reflexes should be elicited by touching the eyelids and observing a blink response. The ‘dazzle’ reflex, a subcortical reflex, may be evaluated, using a bright, focal light source that is shone into the eye, causing the horse to squint or blink.
