Glaucoma is a condition where the pressure inside your eye becomes too high.  The increase in pressure can damage the optic nerve and cause vision loss and blindness.

The symptoms generally start so slowly that you may not notice them.

There’s no cure for glaucoma, but early treatment can often stop the damage and protect your vision. 

There are two main types of glaucoma:

Open-angle glaucoma. This is the most common type of glaucoma and is sometimes also referred to as wide-angle glaucoma. A clear fluid flows continuously in and out of the anterior chamber of the eye and nourishes nearby tissues. In open-angle glaucoma, even though the angle formed by the iris and cornea  is “open,” the fluid passes too slowly through the meshwork drain structure in your eye.  This causes a gradual increase in pressure. About 90% of all cases of glaucoma are open angle.

Narrow-angle glaucoma. With this type of glaucoma, the eye doesn’t drain like it should because the angle between your iris and cornea becomes too narrow. This can cause a sudden increase in pressure within the eye.

People with open-angle glaucoma experience no symptoms in the beginning. It causes no pain, and your vision remains unaffected. That is why glaucoma is often called the "silent thief of sight". The first symptom of open-angle glaucoma is a loss of side or peripheral vision which is why most people don't notice it until significant damage has occurred.

Symptoms of angle-closure glaucoma usually happen more quickly and are more noticeable. Damage to the optic nerve can happen quickly with this type of glaucoma. If you have any of these symptoms, get medical help right away:

• Eye pain that comes on suddenly
• Eye tenderness or redness 
• Nausea or vomiting
• Blurry vision
• Seeing halos around lights