The ocular fundus is the back of the eye opposite the pupil and includes the retina, the membrane between the retina and the white of the eye (the choroid), and the optic disk. Diseases of the ocular fundus may occur on their own or as a part of generalized diseases. Inherited abnormalities, trauma, metabolic disturbances, generalized infections, tumors, blood disorders, and nutritional deficiencies are possible underlying causes for diseases of the retina in all species.

Inflammation of the Retina and Choroid (Chorioretinitis)

Inflammation of the retina and choroid is frequently a result of a generalized infection. It is important as both a convenient diagnostic clue and a predictor of visual function. Unless the abnormalities are widespread or involve the optic nerve, they often are “silent.” Signs of inflammation include swelling, bloodshot eyes, discharge from the eyes, and nodules or masses in the eye itself.

Your veterinarian will look for certain characteristic lesions in the eye. These include “bullet-hole” lesions (which suggest infection with equine herpesvirus), diffuse lesions (which may be caused by inflammation or severe head trauma), and “horizontal band” lesions (which may be caused by blockage of the blood vessels).

Inflammation of the retina and choroid may be present with bacterial, algal, and fungal infections, or caused by trauma or parasites. Therapy is directed at the underlying generalized disease.

Retinal Detachments

When the retina become detached, it is separated from the back of the eye and from part of its blood supply, preventing it from functioning properly. In horses, detachment of the retina occurs with chorioretinitis, trauma, surgery, and low pressure within the eye.

Signs that the retina has become detached include excessive or prolonged dilation of the pupil, pupils of different sizes, vision impairment, and bleeding within the eye. Eye examinations need to be performed to confirm the diagnosis.

Detachments of the retina are treated medically with therapy directed at the primary disease or surgically to correct the detachment. Your veterinarian will select the treatment approach most appropriate for your horse's condition.

Last full review/revision July 2011 by Kirk N. Gelatt, VMD; David G. Baker, DVM, MS, PhD, DACLAM; Steven R. Hollingsworth, DVM, DACVO