Glaucoma forms

There are several forms of glaucoma, including the following:

• Open-angle. In this most common form of glaucoma, the angle where the cornea and the iris meet is open, but the aqueous humor fluid passes too slowly through the meshwork drain. As a result, the pressure in the eye gradually increases, compressing cells in the optic nerve. If left untreated, the compression eventually will cause the optic nerve cells to die, producing blindness.
• Open-angle glaucoma occurs in about one percent of all Americans age 50 and older, according to the Glaucoma Foundation. This type of glaucoma is the leading cause of blindness among African Americans, occurring six to eight more times more often, and at earlier ages than in Caucasians, reports the American Academy of Ophthalmology. Early detection is essential to managing open-angle glaucoma and minimizing vision loss. Treatments include medications in the form of eye drops and pills to reduce the amount of aqueous humor in the eye or improve its drainage, both of which help reduce intraocular pressure. Surgery, either by using a laser or by conventional means, also may be recommended.
• Angle-closure. This type of glaucoma affects nearly 500,000 people in the U.S. according to the Glaucoma Foundation. It occurs when the angle between the iris and the cornea is closed, and the aqueous humor cannot drain, producing high eye pressure. This form of glaucoma is more common among people of Asian or Eskimo descent, especially older women. Other risk factors include old age, a family history of the condition and farsightedness.

Angle-closure glaucoma occurs in two forms, acute and chronic. The acute version can be a sudden, painful attack requiring emergency treatment. The chronic version occurs over time, producing no recognizable symptoms before vision is lost.

People with angle-closure glaucoma tend to have a smaller-than-average anterior chamber, and the angle between the iris and the cornea where the aqueous humor drains is also smaller. When the lens naturally grows larger with advancing age, the aqueous humor has difficulty flowing in the tight space, causing the fluid to build up behind the iris, narrowing the angle even more. When the pupil dilates, such as when entering a dark room, or when experiencing anxiety or stress, the angle narrows even further, and the iris is forced against the trabecular meshwork, stopping drainage. Without drainage, pressure in the eye squeezes and damages the optic nerve.

In acute angle-closure glaucoma, intraocular pressure rises suddenly, producing pain. The eye turns red, the cornea swells and clouds, vision may be blurred, and lights may appear as if they have halos. Treatment with eye drops that help reduce the eye's production of aqueous humor and constrict the pupil may stop an acute attack. Surgery to improve the flow of the aqueous humor is usually recommended.

In chronic angle-closure glaucoma, the iris gradually closes over the drain, causing no recognizable symptoms. As this occurs, scars form between the iris and the drain, eventually blocking it and driving up intraocular pressure. Treatment may include eye drops and surgery.

Although rare in women, a problem called pigment dispersion syndrome can cause angle-closure glaucoma. The syndrome occurs when grains of pigment on the back of the iris flake off into the aqueous humor, eventually clogging the drainage meshwork and raising eye pressure. The syndrome produces no noticeable symptoms, but can be detected and monitored in routine eye examinations. About 30 percent of patients with pigment dispersion syndrome develop angle-closure glaucoma, according to the Glaucoma Research Foundation.

• Normal-tension. Some people with normal eye pressure develop glaucoma, a disease known as low-tension or normal-tension glaucoma (NTG). The Glaucoma Research Foundation estimates that of the three million Americans with glaucoma, about 25 percent to 33 percent may have this form of disease in which eye pressures are within the normal range, but the optic nerve progressively deteriorates. The progression of the disease is faster in those who have the specific risk factors for progression, namely, migraine, disc hemorrhage (a very small bleed on the optic disc, most often seen in those with NTG as opposed to other forms of glaucoma), female gender and racial heritage. Research is continuing on this form of glaucoma, which is thought to be related to poor blood flow to the optic nerve.