Over 2 million Americans have glaucoma, and half of them are unaware that their vision is slowly deteriorating, according to the Glaucoma Research Foundation. Glaucoma is a leading cause of blindness, marked by optic nerve damage that results in irreversible vision loss. Everyone is at risk for glaucoma, from prenatal children to senior citizens. While the vision loss cannot be fixed, early detection and intervention can prevent eye damage from progressing into blindness.

Your eye is filled with a liquid called intraocular fluid of aqueous humor. Parts of your eye constantly produce this fluid to keep your eye clear and your vision healthy. As fluid enters your eye, intraocular pressure (IOP) builds, just as filling a bag with water increases the pressure in that bag. A drainage system clears any excess liquid, preventing a build-up. This drainage keeps the eye pressure at a healthy level. If the drains begin to clog and dysfunction, fluid stays in the eye and the IOP rises accordingly. Eventually, the pressure can damage your eye’s nerve fibers, including the optic nerve. Once enough damage has occurred, you may experience vision loss and eventually blindness.

Glaucoma is a broad term that describes a group of eye diseases. There are two main types of glaucoma: open angle and angle closure. Open angle glaucoma accounts for 90 percent of glaucoma cases, according to the Glaucoma Research Foundation. The eye’s drainage system slowly clogs and the IOP rises gradually, resulting in progressive vision loss. Angle closure glaucoma, on the other hand, is marked by a sudden blockage and an immediate rise in IOP. Also known as acute glaucoma, angle closure causes urgent vision problems.

The signs of glaucoma vary according to the type. Open angle glaucoma develops so gradually that many people do not even recognize their own vision loss. The first signs may be worsening peripheral vision, resulting in tunnel vision. Angle closure glaucoma presents immediate symptoms, including a sudden onset of vision loss or disturbance, severe eye pain, nausea and vomiting. Angle closure glaucoma requires urgent medical attention. The symptoms of childhood glaucoma vary from child to child, but the most common sign is a cloudy cornea. For any type of glaucoma, by the time symptoms appear, the eye has already been damaged. Regular eye exams can help detect glaucoma early and prevent the disease from progressing.

There are a number of risk factors that make one person more likely to have glaucoma than another. While children can be born with glaucoma, the disease typically affects people over 60 years old. Race plays a factor as well. Glaucoma is six to eight times more common in black people than white people, reports the Glaucoma Research Foundation. A family history of glaucoma can also put you at risk, as some forms of open-angle glaucoma are hereditary. Additional risk factors include the use of steroids, hypertension and severe nearsightedness.

There are a number of treatments available, which range in level of medical involvement. Eye drops are the least invasive form of treatment. Drops can decrease the amount of fluid the eye makes and possibly help the eye’s drainage system. Oral medication may also be prescribed to combat high eye pressure.

Laser surgery is a popular surgery for treating glaucoma, and there are individual forms designed to address the different types. Lasers are typically used to burn a small hole in your eye tissue, opening the fluid channel and helping to drain the liquid. If medications or laser surgery are unsuccessful, doctors may attempt conventional surgery. One common procedure known as a trabeculectomy or sclerotomy involves creating a new drainage hole, through which eye fluid can flow back into the blood stream.

While these measures can lower eye pressure and prevent further damage, they cannot reverse vision loss. Other tools such as eye glasses, contact lenses or tinted lenses may help with the problems caused by glaucoma.