Cats, like people, can develop glaucoma. Glaucoma occurs when an imbalance in production and drainage of fluid in the eye (aqueous humor) causes a buildup of fluid that increases eye pressure to unhealthy levels. The increased pressure can cause the destruction of the retina and optic disk (the spot where the optic nerve enters the eye).
Glaucoma occurs less often in cats than in dogs. It usually develops after inflammation of the anterior uvea Inflammation of the Anterior Uvea The uvea (or the uveal tract) is the colored inside lining of the eye consisting of the iris, the ciliary body, and the choroid. The iris is the colored ring around the black pupil. The ciliary... read more or tumors, although primary (open-angle) glaucoma does occur on its own, particularly in the Siamese breed. Initial signs of glaucoma include a dilated, unmoving or slow-moving pupil; redness in the whites of the eyes; swelling and discoloration of the cornea, and a firm eyeball. Prolonged increases of pressure within the eye can result in enlargement of the eyeball, displacement of the lens, and breaks in a membrane of the cornea. Pain usually shows itself as behavioral changes and occasional pain around the eye rather than by spasmodic winking.
If your cat displays any signs of glaucoma, it should be seen by a veterinarian immediately. It is important to decrease the pressure within the eye as quickly as possible to minimize damage. Treatment may require a combination of surgery and medications to reduce eye pressures, preserve vision, and manage pain. In animals with glaucoma caused by anterior uveitis, it is necessary to reduce inflammation and treat the underlying cause. Glaucoma usually requires longterm management. If the affected eye is permanently blind, surgery may be performed to remove the painful eye.
Also see professional content regarding glaucoma Glaucoma in Animals Acute glaucoma in a Cocker Spaniel's eye: episcleral injection and diffuse corneal edema are visible. The pupil is dilated. This dog had an intraocular pressure of 55 mm Hg (normal is < 20mmHg)... read more 
.
