Results--Ocular Hypertension Treatment Study (OHTS)
Glaucoma is a group of diseases that can damage the eye's optic nerve and result in blindness. Open-angle glaucoma, the most common form, is one of the leading causes of blindness in the United States, particularly among African Americans. Glaucoma usually has no early symptoms, and by the time people experience problems with their vision, they usually have a significant amount of optic nerve damage.
How Open-Angle Glaucoma Develops
Increased pressure inside the eye is frequently associated with open-angle glaucoma. In the front of the eye is a space called the anterior chamber. A clear fluid flows continuously in and out of this space and nourishes nearby tissues. The fluid leaves the anterior chamber at the angle where the cornea and iris meet. When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.
Open-angle glaucoma gets its name because the angle that allows fluid to drain out of the anterior chamber is open. However, for unknown reasons, the fluid passes too slowly through the meshwork drain. As the fluid builds up, the pressure inside the eye rises. Elevated eye pressure is believed to damage the optic nerve, but the mechanism is still unknown. A healthy optic nerve is necessary for good vision. When the optic nerve is damaged, vision loss is the result.
At first, open-angle glaucoma has no symptoms. People are not aware that glaucoma is affecting their vision, and there is no pain. When glaucoma remains untreated, people may notice that although they see things clearly in front of them, they miss objects to the side and out of the corner of their eye. Without treatment, people with glaucoma may find that they have no side vision. Over time, the remaining vision may decrease until there is no vision left.
The Ocular Hypertension Treatment Study
Initial results of the Ocular Hypertension Treatment Study, published in 2002, found that eye drops used to reduce pressure inside the eye were effective in delaying the onset of primary open-angle glaucoma. Researchers found that after five years, treatment reduced the onset of primary open angle glaucoma by more than 50 percent. The study examined 1636 people 40-80 years of age who had elevated eye pressure but no signs of glaucoma. Half were assigned daily eye drops, and the other half were assigned to observation (no medication). In the medication group, treatment reduced eye pressure by approximately 20 percent. The Ocular Hypertension Treatment Study was the first large-scale study to demonstrate that lowering eye pressure can safely and effectively delay and possibly prevent the disease.
Because glaucoma is a leading cause of blindness and visual impairment among African Americans, researchers wanted a more definitive answer about the effects of early treatment in this subgroup. After OHTS' initial results, researchers continued to follow the African Americans in OHTS and found that pressure-lowering eye drops reduced the development of primary open-angle glaucoma by almost 50 percent.
Several significant risk factors are associated with the development of glaucoma. These include older age, family history of glaucoma, and diabetes, as well as ocular risk factors, such as higher eye pressure, certain characteristics in the anatomy of the optic nerve, and thinness of the cornea. The OHTS underscores the importance of assessing all of these risk factors in the management of individual patients rather than relying on the perceived or self-reported "race" of that individual.