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 following inflammation of the anterior uvea (see Eye Disorders of Cats: Inflammation of the Anterior Uvea) or tumors, although primary (open-angle) glaucoma does occur on its own, particularly in the Siamese breed. 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.
Treatment may require a combination of surgery and medication (see Eye Disorders of Dogs: Glaucoma in Dogs).
Last full review/revision July 2011 by Kirk N. Gelatt, VMD; David G. Baker, DVM, MS, PhD, DACLAM; A. K. Eugster, DVM, PhD