Primary Open-Angle Glaucoma

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, the fluid in the eye's front (anterior) chamber between the clear cornea and the colored iris (aqueous humor) can't filter through an area where it needs to pass (filtration angle). This occurs because the drainage channels (trabecular meshwork) 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 IOP 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 high doses for prolonged periods, this can increase your risk as well. Other medical conditions related to 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 and siblings have the disease.
   

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.

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.