Canine Glaucoma

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Lisa K. Goldstein, D.V.M.

Taffy is a frequent visitor to our veterinary clinic. At only six years of age, the sweet cocker spaniel already has a very thick medical chart thanks to a long history of skin allergies and itchy ears. So when she started pawing at her right eye and rubbing her face on the carpet, her guardian assumed that her allergies were acting up. But the next morning Taffy wouldn’t come out from under the bed. When she finally did, she seemed to be in pain. Her guardian noticed that her eye looked cloudy, so she rushed her to see me.

Canine Glaucoma

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Normally a very friendly dog, Taffy growled when I tried to pet her. I noticed that the whites of her eyes were red and inflamed. There was a bluish tint to one of her eyes, and the pupil was dilated. I tested the intraocular pressure (IOP) in the sore eye with a tonometer, a blunt-tip instrument that gently touches the cornea and provides a digital measurement of the IOP. Taffy’s diagnosis: glaucoma, a vision-threatening elevation of IOP inside the eye. I immediately began treatment to try to relieve the pain and save her vision.

Recognizing the Signs
Taffy’s symptoms were very common for a dog with acute or sudden-onset glaucoma. Certain breeds are commonly affected by this disease, but any dog – purebred or mixed – can be affected. In a normal eye, fluid (or aqueous humor) is produced behind the iris (the colored area of the eye), then flows through the pupil and drains from the eye at a point where the clear cornea and iris meet. This area, called the drainage angle, is where the aqueous humor rejoins the blood. When the drainage of the aqueous humor is blocked, pressure builds up inside the eye, compresses the optic nerve and results in pain and, eventually, blindness.

Glaucoma is often classified as primary and secondary. Primary glaucoma, as in Taffy’s case, means there is no underlying disease. Secondary glaucoma is caused by an underlying disease, which can stem from chronic infection, irritation from foreign objects, injury to the eye or tumors inside the eye. Time is the most critical factor in treating glaucoma. In as few as 24 hours of increased IOP, irreversible damage can be done to the optic nerve, so it’s important to recognize the warning signs. Symptoms of glaucoma include a dilated eye that doesn’t respond to bright light; a red or swollen eye; a bluish tint or haze to the eye; and pawing or rubbing at the eye. If you notice any of these signs in your dog, seek immediate veterinary care.

If your pet is diagnosed with glaucoma and signs have been present for fewer than 48 hours, emergency treatment must begin immediately to save the vision in that eye. Drugs should be given intravenously to reduce the IOP, and eyedrops should be used to decrease the amount of aqueous humor produced or to increase outflow of the humor. Once the IOP is stabilized, your pet should see a veterinary ophthalmologist to discuss long-term treatment. Unfortunately, it’s very difficult to control canine glaucoma with medication. New drugs are being studied, but surgery is still preferable for long-term control.

Treatment Options

Glaucoma or Cataracts? It’s easy to confuse the two because they both give the appearance of a bluish eye. The difference is that a cataract is a syndrome of many types of lens disorders, and its onset is usually gradual and rarely painful. It’s still important to see a veterinarian if your pet displays symptoms because cataracts can be treated with prompt care.

In animals with primary glaucoma who can still see, laser surgery is used to kill off the ciliary body (the area just behind the iris where the aqueous humor is produced) and thus decrease the fluid production. This surgery is also recommended as a preventative method in the “good” eye of a pet who has glaucoma and is blind in one eye. Alternatively, cryosurgery, a freezing procedure used to decrease intraocular fluid in the eye, may be used in an eye that still has vision. If vision is already lost, however, surgical procedures, such as removing the eye and suturing the eyelid shut, are performed to eliminate pain. For elderly pets, antibiotics can be injected into the eye to kill the ciliary body and stop production of aqueous humor.

Thanks to the quick thinking of her guardian, Taffy’s vision was restored to 75 percent one week after surgery. She gets drops in her good eye to try and keep it glaucoma-free. Save for the occasional itch, Taffy is a healthy example of good parenting.

Dr. Goldstein is a veterinarian practicing in southern California.