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Primary Open-Angle Glaucoma

By Gary Heiting, OD

Chronic glaucoma, also known as primary open-angle glaucoma or POAG, often is called "the silent thief of sight" because you have no warning sign, no pain and no hint that anything is wrong.

About half of Americans with chronic glaucoma don't even know they have it.

In open-angle glaucoma, there is an imbalance in the production and drainage of the clear fluid (called the aqueous humor) that fills the eye's anterior chamber.

This may occur because too much aqueous is produced by the ciliary body or the drainage channels (trabecular meshwork) in the anterior chamber are blocked, causing internal eye pressure (IOP) to rise.

As IOP increases, the pressure pushes harder against the nerve fibers of the optic nerve, which transmits images to the brain. This increased pressure reduces the blood supply to the optic nerve, depriving it of oxygen and nutrients. Over time, high eye pressure can cause irreversible optic nerve damage and vision loss.

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. Aging also 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, high blood pressure, narrowed blood vessels (vasospasm) and cardiovascular disease.
• 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 European study published in Investigative Ophthalmology & Visual Science in October 2011. Smoking, alcohol intake and obesity also are potential lifestyle-related risk factors for glaucoma.

Chronic glaucoma gradually reduces your peripheral vision. But by the time you notice it, permanent damage may have already occurred. If your IOP remains high, the damage can progress until significant loss of your peripheral vision develops, and you will be able to see only 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.

As with other forms of glaucoma, your treatment options may include topical glaucoma eye drops. Laser and/or nonlaser glaucoma surgery may also be recommended as a way to control IOP.

About the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care. Connect with Dr. Heiting via Google+.

[Page updated November 2012]