To understand what glaucoma is, you first have to understand how sight works:

1. When light enters your eye, it travels through several inner structures to reach your retina. Your retina is at the back of your eye.
2. Your retina changes the light into electrical signals. It then sends them to your brain via your optic nerve. Your optic nerve is made up of nerve fibers that the signals can travel on.
3. Your brain then translates the electrical signals, so you can understand what you are seeing.

Glaucoma is an eye disease that damages your optic nerve over time. Without treatment, it can cause vision loss and blindness.

Symptoms differ depending on the type of glaucoma you have. Open-angle glaucoma, the most common type in the United States, can progress for years without any signs.

As it progresses, you may experience increasing vision loss, starting with your peripheral vision. Vision changes can be hard to notice because they happen so gradually.

Emergency Symptoms

Primary angle closure glaucoma is a rare but serious condition. Without immediate treatment, it can permanently damage your vision.

If you experience any of these closed-angle glaucoma symptoms, seek emergency care right away:

• Blurry or altered vision, haloes, rainbow effect in vision  
• Intense headache 
• Nausea and vomiting 
• Red eyes 
• Severe eye pain 

Glaucomas are either primary or secondary. Primary glaucomas develop on their own. Secondary glaucomas occur because of other health conditions or features of the eye that may cause the disease.

Researchers do not know what causes primary glaucoma. But a key feature is degeneration of the optic nerve. The pressure of the eye is a risk factor that is related to this degeneration.

High eye pressure happens when eye fluid (aqueous humor) does not drain from your eye normally. This pressure then damages your optic nerve.

Diagnosing glaucoma starts with an eye exam. To see the back of your eye better, your provider dilates your eyes. During eye dilation, your provider painlessly widens your pupils (the black circle in the center of your eye) using special eye drops.

With your eyes dilated, your provider can examine the optic nerve. To ensure the most accurate diagnosis possible, we also use advanced diagnostic tools when needed. These tools include visual field testing and advanced imaging techniques, such as 3D imaging and high-resolution ultrasound.

In the UC Davis Eye Center, our team of nationally recognized glaucoma specialists cares for you. They work together to prevent vision loss and optimize your eye health.

Our eye specialists are active glaucoma researchers. Their role in important national glaucoma clinical trials means your care includes the latest breakthroughs — sometimes before they are available to the public.

It is not possible to prevent glaucoma — but you can prevent the vision loss it causes. That’s why regular eye exams are so important.

At UC Davis Health, our eye specialists give thorough exams using sophisticated diagnostic tools. Their experience helps catch glaucoma early, when treatments can have the most impact. Learn more about our glaucoma care.