Primary Open-Angle Glaucoma
Chronic glaucoma, also known as primary open-angle glaucoma or POAG, is sometimes called "the silent thief of sight" because in the early stages of the disease there are no warning signs — no pain or vision loss or other hints that something is wrong.
Because of this sneaky nature of the disease and the devastating vision loss it can cause as it progresses, it's essential to have routine eye exams to make sure you are not developing early primary open-angle glaucoma.
What Causes POAG?
If vision loss occurs from primary open-angle glaucoma, it usually begins in your peripheral vision and slowly moves centrally.
In some cases, too much fluid (called aqueous or aqueous humor) is produced by the ciliary body inside the eye. But more often, the drainage channels (trabecular meshwork) in the anterior chamber where the aqueous exits the eye become blocked. Whichever cause, the result is that the pressure inside the eye (intraocular pressure or IOP) increases — sometimes to dangerous levels.
As IOP increases, the pressure pushes harder against the nerve fibers of the optic nerve, which transmits visual information to the brain. This deprives the optic nerve of oxygen and nutrients. Over time, high eye pressure can cause irreversible nerve damage and vision loss.
If vision loss occurs from primary open-angle glaucoma, it usually begins in your peripheral vision and slowly moves centrally. Sometimes, people with later stages of POAG may bump into doorways or not see a car in a passing lane because their peripheral vision is significantly affected.
During an examination for glaucoma, your eye doctor will check your IOP and evaluate your optic nerve. If your eye pressure is elevated or your optic nerve looks suspicious, your doctor will likely perform visual field tests and specialized scans of your retina and optic nerve to determine if you have glaucoma.
Open-Angle Glaucoma Risk Factors
Risk factors for chronic or open-angle glaucoma include:
- Age. Your risk for developing open-angle glaucoma increases significantly after age 40 and continues to increase with each additional decade. This is partly because aging can cause drainage channels in the trabecular meshwork to shrink or narrow, which slows the outflow of fluid from the eye.
- Certain medical problems. Diabetes, extreme nearsightedness and previous eye surgery are risk factors for chronic open-angle glaucoma. If you have a condition that requires the use of oral or inhaled steroids, particularly if high doses are needed for prolonged periods, this can increase your risk as well. Other medical conditions that may increase your risk of open-angle glaucoma include migraine headaches, low blood pressure, narrowed blood vessels (vasospasm), cardiovascular disease, and low cerebrospinal fluid pressure (the fluid that bathes the brain and spinal cord).
- Eye abnormalities. Certain abnormalities affecting internal eye structures can cause glaucoma. Pseudoexfoliation syndrome causes proteins in the eye's natural lens, iris and other structures to slough off and clog the eye's drainage system. Glaucoma also can result when a misshapen iris blocks the filtration angle where drainage occurs.
- Race. Chronic glaucoma is three to four times more common in African-Americans than in whites. Also, African-Americans are more likely to develop an aggressive form of the disease at a younger age.
- Family history. Your risk of developing open-angle glaucoma may be three to four times higher if one or more of your parents or siblings have the disease.
- Lifestyle. A sedentary lifestyle without regular exercise could increase your risk for glaucoma, according to a recent European study published in Investigative Ophthalmology & Visual Science. Smoking, alcohol intake and obesity also are potential lifestyle-related risk factors for glaucoma.
|Risk Factor||Category Score|
|Age||0 = younger than 50
1 = age 50 through 64
2 = age 65 through 74
3 = age 75 or older
|Race||0 = Caucasian
1 = Hispanic
2 = African-American
|Family history of glaucoma||0 = none or only in distant relatives
2 = one or both parents with glaucoma
3 = one or more siblings with glaucoma
3 = one or both parents AND one or more siblings with glaucoma
|Last eye examination||0 = within the last two years
1 = two to five years ago
2 = more than five years ago
|Score: Adding the appropriate numbers will determine your risk. High risk is a score of 4 or more; moderate risk is 3; low risk is 2 or less. Source: Glaucoma Service Foundation to Prevent Blindness.|
Chronic glaucoma gradually reduces your peripheral vision. But by the time you notice it, permanent damage may already have occurred. If your IOP remains too high, the damage can progress until significant loss of your peripheral vision develops, and you will only be able to see objects that are straight ahead.
Left untreated, chronic glaucoma can lead to blindness. According to the National Eye Institute, approximately 3 million Americans have open-angle glaucoma and as many as 120,000 are blind from the disease.
About the Author: John Berdahl, MD, is a special contributor and content reviewer for AllAboutVision.com. Dr. Berdahl performs glaucoma procedures, as well as cataract surgery and refractive surgery, at Vance Thompson Vision in Sioux Falls, S.D. Connect with Dr. Berdahl via Google+.
Marilyn Haddrill also contributed to this article.
Page updated December 2017