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Many Causes for Pet's Red Eye

Pet Column for the week of July 26, 1999

Related information:

Services - Ophthalmology

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
By Sarah Probst
Information Specialist

Your pet's red eye may signal a problem requiring treatment from eye drops to emergency
surgery. Here's a peek at some of the causes and treatments for red eyes.

Conjunctivitis "Conjunctivitis-inflammation of the mucous membranes of the eye-is the
most common eye disease of all domestic animals," says Dr. Ralph Hamor, veterinary
ophthalmologist at the University of Illinois Veterinary Medicine Teaching Hospital in
Urbana. Dogs with allergies and purebred cats are prone to conjunctivitis. The eye reddens
because of the increased flow of blood, and you may see swelling of the mucous
membranes. Viruses or bacteria may cause conjunctivitis; parasites and allergies are less
common causes. Discharge may be clear or contain mucus, depending on severity of the

"As a rule of thumb, conjunctivitis itches," explains Dr. Hamor. "Keeping the eye clean and
eliminating the cause of the conjunctivitis with appropriate medication are keys to control."

Keratitis "Chronic superficial keratitis, also know as degenerative pannus, occurs primarily
in German shepherds but occasionally in other breeds," says Dr. Paul Gerding, also a
veterinary ophthalmologist at the teaching hospital. "The disease causes pigmentation and
superficial blood vessels on the eye. It's not that painful but can decrease vision if left

Keratitis also occurs in chronic cases of keratoconjunctivitis sicca (KCS). KCS occurs
when there is not enough moisture in the tear film. A thick, ropy mucous discharge is
associated with this common ophthalmic disorder. In chronic cases, the corneal layer of the
eye becomes infiltrated with blood vessels, pigmented, and harder because of the long-term
irritation. Treatment involves tear stimulants and anti-inflammatories. "Eye ulcers are often
associated with keratitis and may require surgical repair," adds Dr. Gerding.

Inflammation of the eyelids and cherry eye Eyelids may become inflamed from
dermatitis; a bacterial, parasitic, or fungal infection; a metabolic or immune system problem;
neoplasia; trauma; or sun damage. Treatment varies by exact diagnosis.

"Cherry eye" is a prolapse of the gland of the third eyelid. It commonly affects young dogs,
especially beagles, cocker spaniels, Pekingese, and bulldogs. "The gland protrudes and
becomes irritated and inflamed," explains Dr. Hamor. "If one eye has cherry eye, the other
eye could be predisposed to it as well." Treatment for cherry eye is surgical replacement of
the gland.

Scleritis "Scleritis usually involves only one eye. The red area may develop suddenly and
be lumpy, immovable, and hard," says Dr. Gerding. It is often treated with steroids.

Uveitis "Inflammation of part or all of the uveal tract is a very common ocular problem in
domestic animals and human beings," says Dr. Hamor. The uvea surrounds much of the eye
with blood vessels. Your pet may show signs of eye pain such as an overflow of tears,
eyelid spasms, sensitivity to light, recession of the eyeball into the orbit, and small pupils. If
untreated uveitis harms vision.

Glaucoma "Glaucoma, if not treated immediately, can lead to irreversible blindness. A dog
with glaucoma deserves the same emergency status as a dog that has been hit by a car,"
says Dr. Hamor. "Veterinarians may see glaucoma in 8 percent of all canine patients."

Glaucoma is an elevation of pressure in the eyeball because an obstruction prevents fluids in
the eye from flowing out. Signs of glaucoma include cloudy pupils, large pupils, and
redness. "Treatment of acute glaucoma by the primary care veterinarian should be directed
toward one goal-rapid reduction of pressure in the eye before permanent blindness occurs.
Medical therapy must be started immediately after diagnosis in order to preserve vision,"
says Dr. Hamor.

Blood in the anterior chamber of the eye Bleeding in the eye generally results from
trauma, inflammation, or other vascular defects. Hemorrhage from trauma may need to be
surgically corrected. Uveitis and neoplasia can bring about growth of new blood vessels,
which are inherently leaky and may cause blood to accumulate. If the eye has progressed to
glaucoma, removal of the eye may be necessary.

For further information about a suspected eye problem in your pet, contact your local