Glaucoma is a group of diseases that damages the eye's optic nerve. The optic nerve transmits visual information to the brain, allowing us to see. Because glaucoma often progresses slowly, affecting just peripheral or side vision, people with glaucoma can lose most of their vision before they even experience any symptoms. Central vision, the vision used to read, drive or watch TV, is unaffected until the disease is advanced.
Your eye constantly makes aqueous humor. As new aqueous flows into your eye, the same amount should drain out. The fluid drains out through an area called the drainage angle. This process keeps pressure in the eye (IOP) stable. But if the drainage angle is not working properly, fluid builds up. Pressure inside the eye rises, damaging the optic nerve.
The optic nerve is made of more than a million tiny nerve fibers. It is like an electric cable made up of many small wires. As these nerve fibers die, you will develop blind spots in your vision. You may not notice these blind spots until most of your optic nerve fibers have died. If all the fibers die, you will become blind.
There are two major types of glaucoma:
Primary open-angle glaucoma
This is the most common type of glaucoma. It happens gradually, where the eye does not drain fluid as well as it should (like a clogged drain). As a result, eye pressure builds and starts to damage the optic nerve. This type of glaucoma is painless and causes no vision changes at first. Some people can have optic nerves that are sensitive to normal eye pressure. This means their risk of getting glaucoma is higher than normal. Regular eye exams are important to find early signs of damage to their optic nerve.
Narrow-angle glaucoma
This type happens when someone's iris is very close to the drainage angle in their eye. The iris can end up blocking the drainage angle. You can think of it like a piece od paper sliding over a sink drain. when the drainage angle gets completely blocked, eye pressure rises very quickly. This is called an acute attack. It is a true eye emergency, and you should call your opthomalogist right away or you might go blind.
Here are the signs of an acute angle-closure glaucoma attack:
Your vision is suddenly blurry
You have severe eye pain
You have a headache
You feel sick to your stomach (nausea)
You throw up (vomit)
You see rainbow-colored rings or halos around lights
Many people with angle-closure glaucoma develop it slowly. This is called chronic angle-closure glaucoma. There are no symptoms at first, so they don't know they have it until the damage is severe or they have an attack.
Angle-closure glaucoma can cause blindness if not treated right away.