Say the word "glaucoma," and people are more likely to think of their grandmother than their Great Dane. However, glaucoma also affects animals of all types, including dogs.
Glaucoma occurs as a result of increased pressure within the eye. Cells inside the eye produce a clear fluid, known as the aqueous humor, which feeds the tissues inside the eye, as well as keeping the eye in its proper shape. Normal eye pressure is maintained through a balance of fluid created by the eye and drainage provided by ducts within the eyeball and surrounding structures With glaucoma these drains become blocked, yet the eye continues to produce fluid, increasing the internal pressure. Over time, this can cause the eye to stretch and enlarge, causing pain and damaging vision.
In animals, glaucoma falls into two classifications - primary and secondary. Primary glaucoma is inherited and occurs in many different breeds, especially American Cocker Spaniels, Basset Hounds, Chow Chows, Labrador Retrievers and Shar-Peis. It's also found in colder-climate dogs such as Huskies and Elkhounds. Over time, glaucoma-related internal pressure inside the eyeball causes damage to the optic nerve and decreases blood flow to the retina. Both of these result in vision loss. In severe cases, if the pressure is very high, permanent blindness can occur within a matter of hours. With primary glaucoma, the condition usually begins in one eye and then spreads to the other, eventually leading to complete blindness.
With secondary glaucoma, the drainage problem is caused by a variety of eye diseases and injuries, including advanced cataracts, cancer in the eye, inflammation inside the eye (uveitis), tears in the eye's lens (luxation or subluxation), scarring and retinal detachment. The condition also is painful, more so in pets than in humans, because the pressure inside the eye is higher.
Glaucoma pain is often experienced in the form of headaches or migraines in humans. In your dog, look for red or bloodshot eyes, a cloudy-looking cornea, decreased activity, decreased appetite, irritability and a lack of interest in playing or exercising. Some may paw at their eye, rub their eye on the carpet or against furniture, or the eye may appear swollen and the pupil dilated. Keep in mind, though, that your dog can't tell you when its eye is hurting, and many times the first affected eye has lost its sight by the time glaucoma is diagnosed.
Treatments differ for primary and secondary glaucoma, which makes determining the exact cause of the condition important. Veterinary ophthalmologists use a variety of instruments and examinations to determine the type and cause of glaucoma in animals. Eye drops and pills can be prescribed to increase or decrease fluid drainage from the eye. They are helpful, but usually don't control canine glaucoma for any significant amount of time.
Surgically opening the blocked drains and keeping them open is the ideal glaucoma treatment, but it can be difficult to achieve. Therefore many therapies are designed to relieve the pressure by decreasing fluid production in the eye. The goal is to prevent or delay the development of glaucoma in the eye that still has vision.