Glaucoma is an increase in intra-ocular pressure in the eye. It is caused by inadequate drainage of fluid in the eye. Symptoms include eye pain, watery discharge from the eye, swelling or bulging of the eyeball, cloudy appearance of the eye, and blindness. Intra-ocular eye pressure is measured using a tonometer. 

Detected early, glaucoma can often be treated effectively, preventing the blindness and pain associated with this commonly overlooked condition in senior pets. Many breeds of dogs and cats are at higher risk.