A small amount of dark reddish or brown eye discharge in cats is not unusual. Cats normally produce tears that flow down small ducts in the inner corner of their eyes. Like humans, their eyes may crust with dried tears when they sleep. However, if the discharge is thick, does not wipe away easily with a warm, wet cloth, or is noted along with other symptoms, it is time to take your pet to the vet.
Conjunctivitis is inflammation of the conjunctiva, the mucus membrane that covers the eye and lines the lids. Conjunctivitis can cause a red, green, yellow or brown eye discharge in pets and swelling around the eyes. Causes include allergies, physical irritation, tumors, inherited conditions and infections. Common conjunctivitis-related infections in cats include feline infectious rhinotracheitis, also called feline herpesvirus, feline calcivirus, feline mycoplasma and feline chlamydia. Feline mycoplasma and chlamydia are treated with topical antibiotic drops or ointments. Feline rhinotracheitis infections can be reduced through vaccination and treated with anti-viral drugs and l-lysine supplements, but cannot be cured -- infected cats may experience periodic flare ups throughout their lives.
Epiphora is excessive tearing. It is caused by obstruction to the tear ducts in the inner corners of a cat's eyes or because the cat produces more tears than the ducts can successfully drain. Obstruction and excessive tearing may be caused by foreign objects, such as hairs, or by physical trauma or infection. An affected cat may have discharge caked in the inner corners of his eyes or streaks down his face. The discharge may range from clear to dark brown and may irritate the skin. If the discharge is accompanied by other symptoms or appears chronically, veterinary care is needed for proper diagnosis and treatment.
Although rare in cats, eye discharge can be a symptom of glaucoma. Glaucoma is swelling and excessive pressure within the eye due to abnormal drainage. This pressure is extremely painful and can crush the eye's internal structures, leading to vision problems and ultimately blindness. Glaucoma can result from eye deformities or from disease, tumors or physical trauma. Your vet will recommend medical or surgical treatment depending on the cause of your cat's glaucoma and how advanced it is.
Uveitis is the inflammation of the middle layers of the eye, which surround the pupil and include the pigmented iris. Along with excessive tearing, a cat with uveitis may be sensitive to light and his eyes may appear cloudy. Uveitis is a painful condition and can cause blindness if left untreated. Feline uveitis may be caused by a foreign body in the eye, physical trauma or infection and can lead to glaucoma. Treatment includes medication with corticosteroids and antibiotics.
Keratitis is inflammation of the cornea -- the clear outer surface of the eyeball often mis-identified as the "lens." It has a number of causes -- including physical trauma and feline herpesvirus infection -- and requires veterinary treatment. Along with eye discharge a cat with keratitis may be sneezing, have a runny nose and may run a fever.