First, get an examination by a veterinary ophthalmologist. There are eye drops containing dorzolamide and/or timolol that can reduce the eye pressure. Cortisone drops can reduce the inflammation. There are surgical procedures that can be helpful. In advanced cases where vision has already been lost there are injections into the eyes that can stop the production of eye fluid to reduce the pressure and alleviate the pain. This treatment will typically cause the eye to shrink and the cat is more comfortable.