The conjunctiva is a thin membrane that lines the inside of the eyelids and extends to the cornea of the eye. It plays a role in creating tears, providing protection for the eye from foreign invaders, and healing of the cornea after injury. It is important to identify and treat problems of the conjunctiva, because some can indicate generalized disease, while others can lead to blindness if not treated.

Conjunctivitis (Pink Eye)

Conjunctivitis, also known as pink eye, can occur as a result of many different diseases that affect the eye or even the whole body. The causes vary from infections to environmental irritants. The signs are excess blood flow to the eye, swelling of the tissue around the cornea, discharge from the eye, and mild eye discomfort. The appearance of the conjunctiva usually is not enough, by itself, to allow your veterinarian to diagnose the cause with only a physical examination. A specific diagnosis often requires a medical history, tests on conjunctival scrapings, Schirmer tear test, and occasionally biopsy.

Conjunctivitis in only one eye may result from a foreign object, inflammation of the tear sac, or dry eye (see Eye Disorders of Horses: Dry Eye (Keratoconjunctivitis Sicca)). Conjunctivitis occurring in both eyes is commonly caused by infection with a virus or bacteria. Environmental irritants and allergens are other common causes of conjunctivitis. If a mucus and pus-filled discharge is present, your veterinarian may prescribe a topical antibiotic. However, the antibiotic alone may not bring about healing if other factors are involved. Your veterinarian will also check for foreign objects in the eye, environmental irritants, parasites, and defects of eyelid shape, outline, or form, as these factors also contribute to pink eye. Because conjunctivitis can have multiple causes, your veterinarian may prescribe a combination of treatments.

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