The early signs of glaucoma in dogs and cats can include:
Glaucoma, which causes increased pressure in the eye, will eventually cause the eye to swell. Unfortunately, a bulging or swollen eyeball is a very late sign; that is, your pet's eye won't appear bulging until it has had glaucoma long enough to have serious problems and probable blindness.
There are also several other diseases that can make the eyeball look swollen, such as a tumor or an abscess behind the eye. Your veterinarian will diagnose your pet's problem and recommend treatment.
The only way to tell for sure if your pet has glaucoma is to have your veterinarian measure your pet's eye pressure with a tonometer.
Cats seldom develop glaucoma, and when they do, it is difficult to realize there is a problem because cats hide their symptoms.
Glaucoma is diagnosed with a tonometer that measures pressure within the eyeball. There are three types of tonometers: one blows a puff of air onto the eyeball and uses the indentation as a gauge of pressure. Another tonometer presses a small, flat disk against the eyeball to register pressure. Your veterinarian may put a drop of anesthetic in the eye first. The third method, called Mueller, is electronic. To use any of these methods, your veterinarian may place your pet on his or her back, which often allows your pet's eye to open more easily.