Cat sitting in the snow.

Cat Glaucoma

Glaucoma is a condition characterized by an increase in fluid pressure from the aqueous humor within the eye(s).

In the normal eye, pressure and aqueous levels are maintained at a constant plateau by the continual drainage of excess aqueous humor out of the eye through tiny ports (drainage angles) located where the edge of the iris meets the cornea.

If this drainage is obstructed or altered in any way, a rise in pressure within the eye can result. Unfortunately, even short-term rises in this pressure can lead to irreversible damage if not detected and treated in a timely fashion.

Conditions such as a buildup of inflammatory material within the eye, luxation of the lens due to trauma or cataracts, and synechia, where the iris “sticks” to the lens or cornea, can all effectively prevent the normal drainage of the aqueous humor from the eye.

Finally, allergies and overactive immune system responses are also thought to be important precursors to glaucoma in cats. Clinical signs of a glaucomatous eye include a marked redness affecting both the conjunctival tissue and the sclera; a blue, hazy cornea; a dilated, unresponsive pupil; and apparent blindness due to the pressure the fluid is placing on the optic nerve.

In instances where the glaucoma has been present for quite some time, enlargement of the affected eyeball might become noticeable, and actual rupture of the cornea could occur. Diagnosis of glaucoma can be easily confirmed by a veterinarian through the use of an instrument called a tonometer.

This instrument, when placed directly on the surface of the cornea, measures the exact pressure within the eye. If the pressure reading is indeed elevated, then treatment should be instituted immediately to prevent lasting damage to the eye.

Treatment for glaucoma is aimed at decreasing the pressure within the eye to an acceptable level as quickly as possible, and then stabilizing this pressure to prevent future increases.

Drugs designed to quickly draw fluid out of the eye and into the bloodstream will initially be used to reduce the pressure within a pet’s eye(s).

Other drugs that act by decreasing the production of aqueous humor and by increasing the size of the drainage angles are then prescribed for the long-term management and prevention of recurrence.

At the same time, anti-inflammatory medications can be used topically on the eye to clear up any primary or secondary inflammation that might be aggravating the glaucoma. In instances where a luxated lens is causing the increase in pressure, surgical removal of the offending lens should always be performed.

Cryotherapy (freezing) can be used as well. This involves surgically inserting a special needle within the eye and freezing the cells within the eye responsible for the production of aqueous humor. With this technique, aqueous production can be reduced by up to 30 percent in some patients.