The conjunctiva is a thin membrane that lines the inside of the eyelids and extends over to the cornea of the globe. 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.
Ruptured Blood Vessels (Subconjunctival Hemorrhage)
Ruptured blood vessels beneath the conjunctiva may be the result of trauma, a blood disorder, or certain infectious diseases. This condition, by itself, does not require treatment, but close inspection is necessary to determine if more serious changes within the eye have occurred. If definite evidence or history of trauma is not present, then your veterinarian will perform a complete examination to determine the cause of the spontaneous bleeding.
Swelling of Conjunctival Tissue (Chemosis)
Swelling of the conjunctival tissue around the cornea occurs to some degree with all cases of conjunctivitis, but the most dramatic examples are seen with trauma, a deficiency of proteins in the blood (hypoproteinemia), allergic reactions, and insect bites. Insect bites are treated with topical corticosteroids and usually heal rapidly. In other cases, specific therapy to treat the original cause is required.
Pink Eye (Conjunctivitis)
Conjunctivitis, also known as pink eye, is common in cats. It often occurs as the result of an infection with feline herpesvirus-1, which is extremely widespread among cats. Other causes include various bacterial infections, foreign objects, and 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 scrapings taken from the conjunctiva, 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 Cats: 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, 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, including antibiotic or antiviral therapy.
Conjunctivitis with large amounts of a thick discharge from the eye can occur in newborn kittens. It is usually the result of the same bacteria and viruses that cause infections in adult cats and is treated with topical antibiotics, such as an antibiotic eye ointment.
Last full review/revision July 2011 by Kirk N. Gelatt, VMD, DACVO; David G. Baker, DVM, MS, PhD, DACLAM; A. K. Eugster, DVM, PhD