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You come home from work one day and notice that your pet’s eye is very red. In fact, the eye seems pretty painful. You might wonder if the irritation will just go away on its own, but you decide to take your pet to the veterinarian just to check. Good thing you did as your pet has glaucoma.

It is an understatement to say that eyes are very important. Animals understand their world in many ways. They can smell the details of their world almost as well as they can see the details. In fact, they appear to have abilities that we don’t have, such as sensing a coming seizure or earthquake. But eyes allow animals to see the world around them and to react to it. Vision lets animals function in their world; it helps them find safety, food, and friends.
           
The eye is actually part of the brain! There is a direct connection between the eyeball and the front of the brain. This is through the optic nerve. When we look at something, nerves in the eye turn the picture into electrical signals. These electrical signals travel through the optic nerve to the brain. The brain interprets the signals, allowing us to see.
           
The eye has many parts and there are a lot of unfamiliar names for each part. We will name a few parts of the eye which are important in the development of glaucoma. The normal eye is divided into two sections, a front and a back. The liquid in the front section is called ‘aqueous humor’. Some structures inside the eye do not have blood vessels, so the liquid aqueous humor does the job that blood normally does. It provides nutrients and takes away waste. Aqueous humor is produced behind the iris (the coloured part of the eye). It circulates to the very front of the eye (the cornea) and is absorbed in front of the iris at the ‘filtration angle’.
           
In glaucoma, something blocks the filtration angle. If the filtration angle is blocked, the aqueous humor cannot leave the eye.
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