Increased pressure inside the eye is called Glaucoma. It is fairly common in dogs but can occur in cats. It is extremely painful and if left untreated rapidly causes irreversible blindness.
There are a number of causes. Some dogs have an inherited susceptibility, often associated with luxation of the lens. In some dogs it is caused by trauma or infection. The way it is treated is usually the same initially, but the long term treatment and prognosis depends on the cause.
The most important thing is to correctly diagnose the problem, then treat it appropriately to reduce the pressure inside the eye to safe and comfortable levels. This we do with a tonometer pen (tono pen), which will accurately and repeatedly tell us what the pressure inside the eye is.
You will find that we will measure the pressure inside the eye if we are suspicious of a problem. If we find the pressure is raised, we will usually start your pet on treatment and book them in for repeated measurements every few days or weeks until the pressure is reduced to a safe level.