A normal eye contains fluid called aqueous humor that helps to keep the eye inflated and provide nutrients to the eye's internal structures. When too much of this fluid builds up, the pressure within the eye increases and this is called glaucoma. This increased pressure may be caused by hereditary factors, inflammation of the structures within the eye, disorders of the lens, or tumors. Glaucoma is a serious disorder, which can occur in one eye or both, and may arise quickly or build up slowly over time. Glaucoma is a painful disease and is the leading cause of blindness in middle aged dogs.
Glaucoma has a variety of presentations depending on the severity and how quickly it comes on. Early in the disorder, the eye may appear red, watery, or irritated. As the pressure increases, the affected eye may appear larger than normal and have a bluish or whitish tinge to the eye surface. At this stage, the eye may become very painful. Your pet may be rubbing at the affected eye and may be sensitive to light (winking, squinting, avoidance of sunlight, etc). If left untreated, glaucoma will eventually lead to permanent blindness and rupture of the eyeball itself.
The intraocular pressure of the eye can be measured in a fast, non invasive test. The test is performed by applying a topical anesthetic drop to the eye. Then, an instrument called a tonopen is quickly tapped on the eye surface to read the internal pressure. Several readings are performed per eye and averaged together. Your pet will not be able to feel the instrument and the test only takes a few minutes. All senior dogs (over the age of 7 years) can benefit from an annual glaucoma screening or a test may be recommended on a case-by-case basis if your pet has an eye problem. Cats may be affected by glaucoma, but it is not as common.
Glaucoma is a very serious disorder and treatment should begin immediately to provide comfort and to retain vision. Medical treatment consists of various eye drops or possibly IV medications depending on severity. These medications either decrease the amount of liquid being produced within the eye or they encourage the natural drainage from the eye. Multiple medications may be needed. If medical therapy is not adequate or if the pet is already blind, then surgical treatment which involves removal of the eye may be discussed. Eye removal may seem extreme, but if the eye is no longer visual, surgical removal may be the only method of taking away the pain.
Certain breeds are more predisposed to glaucoma: Akita, Alaskan Malamute, Basset hound, Beagle, Border collie, Boston terrier, Carin terrier, Corgi, Chihuhua, Chow, Cocker spaniel, Dachshund, Dalmation, Springer spaniel, Great Dane, Maltese, Min Pin, Poodle, Scottish terrier, Shih Tzu, Siberian husky, and West Highland white terrier. Among cats, hereditary glaucoma is rare but: Persians, Siamese, and some Domestic Short haired cats may be predisposed.