What To Do If Your Cat Gets Glaucoma
Like their human companions, dogs and cats can lose their vision to glaucoma, but veterinary medicine now offers treatments that preserve an animal's sight. It is important for pet owners to be aware of the symptoms of glaucoma and to act on them quickly because the disease can quickly devastate the eye. Primary glaucoma involves a problem in the way that the eyeball developed. Cases of primary glaucoma generally occur in breeds that are genetically predisposed to suffering from the condition. Primary glaucoma is much more common in dogs than in cats.
What is Glaucoma?
Glaucoma is essentially abnormally high pressure in the eye. A normal eye constantly produces and drains a watery fluid. If a problem develops with the drainage, pressure inside the eye can build up. High pressure causes damage to the optic nerve, which, in turn, causes vision loss.
What Causes Glaucoma?
There are primary and secondary causes of glaucoma:
Secondary glaucoma encompasses many causes, including inflammation that scars the eye and blocks fluid drainage; tumors that "fill-up" the drainage pathway; trauma to the eye that causes it to fill with blood that blocks and scars the drainage pathway; and lens luxation, a shift in the lens that can block a drainage pathway.
Inflammation inside the eye has many causes. In dogs, they include infectious diseases such as fungal disease, tick-transmitted disease and cataracts. For cats, chronic anterior uveitis, an inflammation of the front of the eye, often leads to glaucoma. One or both eyes can eventually be affected depending on the cause of inflammation.
The fluid outflow pathway in the eye is commonly known as the drainage angle. For proper outflow, the angle needs to be open in a way that the fluid will flow through small holes, as in a sieve. In breeds predisposed to glaucoma, there is usually a narrow angle or inadequate holes in the sieve (known as goniodysgenesis).
What to Watch For
A red eye
A very squinty and painful eye
A lot of tearing
A dilated pupil that doesn't react to light
A cloudy (whitish/blue) cornea (front surface of the eye)
A big, bulging eye (a condition known as buphthalmia)
Glaucoma generally only affects one eye initially. Depending on the cause, the other eye may be at risk for developing glaucoma in the future.
Many diseases can cause a red, squinty, teary and cloudy eye, but glaucoma should always be considered as a cause. Frequently, when the pressure is high, pets are in a lot of pain and hold the eye closed or keep the third eyelid (a pink/red membrane) up over the eye making it difficult to assess.
It is essential to evaluate the pupil in a red, squinty, teary eye with or without the cloudy surface appearance. The pupil is the black "hole" in the center of the eye formed by the iris, which is the colored part of the eye. If the pupil is widely dilated (a large black spot with minimally colored parts visible) and it doesn't constrict (get smaller) in response to a bright light, glaucoma is highly possible. When checking the pupil response, don't be confused by the normal reflection of bluish/green or yellowish/orange that is frequently seen shining through the black hole of the pupil.
Assessing vision can be difficult, but is very helpful. Your pet should blink to a bright light shown into the eye. Without creating airflow or touching any whiskers, see if your pet blinks when you wave your hand in front of the eye (known as a "menace test" because your pet is responding to a menacing gesture). You can also throw objects like cotton balls (anything that won't make a sound when it lands) in front of your pet to see if he follows the object. Setting up mazes can also be helpful; move chairs or garbage cans around in a room that is familiar to your pet, and then see if he can navigate across the room. This type of test will be less effective if only one eye is affected.
If you suspect that your pet has an increase in pressure in an eye, it is best to treat the problem aggressively because glaucoma can quickly cause severe damage. You can always stop medications if they aren't needed; you can't go back in time and give medications if they were needed.
After taking a complete medical history and doing a physical exam, your vet or veterinary ophthalmologist may diagnose whether your pet in fact suffers from glaucoma through tests that include a complete eye exam; a check of the pressure inside of the eye (called tonometry); gonioscopy, a test that evaluates the drainage pathway; and ultrasound, which can help identify lenses or tumors that are out of place if the inside of the eye cannot be examined by routine techniques.
Treatment for glaucoma is generally aimed at decreasing the production of fluid inside the eye, increasing the flow of fluid out of the eye and controlling any inflammation inside the eye. Topical medications (drops and ointments placed directly on the eye) and systemic medications (pills or injections) are available.
Surgery may also be recommended. This can include trying to "kill" some of the cells that produce fluid inside of the eye by laser or deep-freeze; trying to create a different drainage pathway; removing the eye; placing a prosthesis in the "shell" of the eye; or injecting a medication into the eye to "kill" the fluid producing cells.
What You Can Do for Your Pet
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical. You should:
Understand the symptoms of glaucoma so that you can catch an increase of pressure in the eye right away. Frequently this applies most to a pet on medical therapy, in which you are trying to maintain some vision in a diseased eye. It also applies when the first eye lost vision very quickly due to glaucoma and you are trying to protect the second eye. Saving vision in an eye with high pressure can be a race against the clock so the "Watch for" symptoms listed above are very important.
Because time is of the essence with this disease, you're the front line of defense when there is a problem until you can get to your veterinarian or veterinary ophthalmologist.
Understand what medications your pet is on and why, and administer them as prescribed by your vet.
Be certain to alert your veterinarian if you are experiencing problems treating your pet. Frequent trips to your veterinarian may be necessary. Medications are frequently adjusted to maintain comfort and/or protect the vision of your pet or to monitor a visual eye if the other eye has gone blind from glaucoma.
Despite treatment, most dogs with glaucoma will be blind in that eye within 36 to 48 months and, if predisposed to glaucoma, will likely fall victim to the condition in their other eye as well. Medications may delay that process. Surgical removal of a blind, painful glaucomatous eye is recommended once all treatment has ended.
If therapy fails, understand that vision loss is not life threatening and the vast majority of animals adjust very well to impaired vision or blindness.