Page 992 - The Veterinary Care of the Horse

cataracts. In carefully selected cases, e.g. some young foals with congenital cataracts,

surgical removal may restore vision. However, this will leave them long-sighted so nearby
VetBooks.ir objects appear out of focus and blurred. Artificial lenses have now been developed for horses
and lens replacement is a possibility for selected cases. Complications of the surgery include

glaucoma and infection which can both cause loss of sight, so this procedure is only
recommended for dense cataracts in suitable patients.

Prognosis

The prognosis is good for small, non-progressive cataracts that have little effect on the
horse’s vision. With progressive cataracts the prognosis is poor. When the cataract occurs

secondary to inflammatory changes within the eye, e.g. recurrent uveitis, the prognosis is
guarded. Animals with hereditary cataracts should not be used for breeding.

EQUINE UVEITIS

When a horse has uveitis, the iris, ciliary body and the choroid (collectively known as the
uveal tract), become inflamed.

Causes

Uveitis can occur as a result of:

• bacterial or viral infection

• a blow to the head
• injuries to, or penetrations of, the cornea

• tumours within the eye

• parasites, e.g. Toxoplasma, larvae of Onchocerca cervicalis.

In some cases the condition may arise due to a reaction of the immune system to bacteria,

viruses or parasites. Alternatively, uveitis can be an autoimmune disease whereby an immune
response is mounted against the horse’s own tissues.

The treatment in every case is aimed at controlling the pain and preserving the horse’s
vision by preventing long-term damage to the eye.

EQUINE RECURRENT UVEITIS