Glaucoma

Glaucoma refers to a category of eye disorders often associated with a dangerous buildup of internal eye pressure, which can damage the eye's optic nerve that transmits visual information to the brain.

With untreated or uncontrolled glaucoma, a person might eventually notice decreased ability to see at the edges of their vision (peripheral vision). Progressive eye damage could then lead to blindness.

In fact, as the second leading cause of blindness, glaucoma creates at least some vision loss in more than half of the approximately 2.5 million Americans estimated to have the eye disease.

Glaucoma Symptoms

Glaucoma is often referred to as the "silent thief of sight," because most types typically cause no pain and produce no symptoms. For this reason, glaucoma often progresses undetected until the optic nerve already has been irreversibly damaged, with varying degrees of permanent vision loss.

But with acute, angle-closure glaucoma, symptoms that occur suddenly can include blurry vision, halos around lights, intense eye pain, nausea, and vomiting.

Types of Glaucoma

The two major types of glaucoma are chronic or primary open-angle glaucoma (POAG) and acute angle-closure glaucoma, with angle referring to the configuration of internal eye structures that drain fluids. Other variations include congenital glaucoma, pigmentary glaucoma, and secondary glaucoma.

Primary open-angle glaucoma (POAG)

About half of Americans with chronic glaucoma don't know they have it. Glaucoma gradually reduces peripheral vision. But by the time it is noticed, permanent damage has already occurred. If the IOP remains high, the destruction can progress until tunnel vision develops, and the person will be able to see only objects that are straight ahead.

Angle-closure glaucoma

Angle-closure or narrow angle glaucoma produces sudden symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea, and vomiting. These signs may last for a few hours, then return again for another round. Each attack takes with it part of the field of vision.

Normal-tension glaucoma

Like POAG, normal-tension glaucoma (also termed normal-pressure glaucoma, low-tension glaucoma, or low-pressure glaucoma) is an open-angle type of glaucoma that can cause visual field loss due to optic nerve damage. But in normal-tension glaucoma, the eye's IOP remains in the normal range. Also, pain is unlikely and permanent damage to the eye's optic nerve may not be noticed until symptoms such as tunnel vision occur.

The cause of normal-tension glaucoma is not known. But many doctors believe it is related to poor blood flow to the optic nerve. Normal-tension glaucoma is more common in those who are Japanese, are female, and/or have a history of vascular disease.

Congenital glaucoma

This inherited form of glaucoma is present at birth, with 80% of cases diagnosed by age one. These children are born with narrow angles or some other defect in the drainage system of the eye. It's difficult to spot signs of congenital glaucoma, because children are too young to understand what is happening to them. Congenital glaucoma typically occurs more in boys than in girls.

Pigmentary glaucoma

This rare form of glaucoma is caused by pigment deposited from the iris that clogs the draining angles, preventing aqueous humor from leaving the eye. Over time, the inflammatory response to the blocked angle damages the drainage system. It is unlikely to notice any symptoms with pigmentary glaucoma, though some pain and blurry vision may occur after exercise. Pigmentary glaucoma affects mostly white males in their mid-30s to mid-40s.

Secondary glaucoma

Symptoms of chronic glaucoma following an eye injury could indicate secondary glaucoma, which also may develop with presence of infection, inflammation, a tumor, or an enlarged cataract.

Medical marijuana

Studies in the early 1970s showed that marijuana, when smoked, lowered intraocular pressure (IOP) in people with normal pressure and those with glaucoma. In an effort to determine whether marijuana, or drugs derived from marijuana, might be effective as a glaucoma treatment, the National Eye Institute (NEI) supported research studies beginning in 1978. These studies demonstrated that some derivatives of marijuana transiently lowered IOP when administered orally, intravenously, or by smoking, but not when topically applied to the eye.

However, none of these studies demonstrated that marijuana -- or any of its components -- could lower IOP as effectively as drugs already on the market. In addition, some potentially serious side effects were noted, including an increased heart rate and a decrease in blood pressure in studies using smoked marijuana.

• Advocates of medicinal marijuana cite evidence that hemp products can lower intraocular pressure (IOP) in people with glaucoma. However, these products are less effective than safer and more available medicines. Most research regarding marijuana use took place before some current medications with fewer side effects were available. The high dose of marijuana necessary to produce a clinically relevant effect on IOP in the short term requires constant inhalation, as much as every three hours. The number of significant side effects generated by long-term oral use of marijuana or long-term inhalation of marijuana smoke make marijuana a poor choice in the treatment of glaucoma. [1]

Links

• Medical Marijuana Glaucoma Research Foundation