Scientists found that daily pressure-lowering eye drops reduced the development of primary open-angle glaucoma in African Americans by almost 50 percent. Primary open-angle glaucoma is the most common form of glaucoma and one of the nation's leading causes of vision loss. Of the African American study participants who received the eye drops, 8.4 percent developed glaucoma. By comparison, 16.1 percent of the African American study participants who did not receive the eye drops developed glaucoma. The study was funded by the National Eye Institute (NEI) and the National Center on Minority Health and Health Disparities (NCMHD), two components of the Federal government's National Institutes of Health.
The results of this study, called the Ocular Hypertension Treatment Study (OHTS), are a followup to initial results released two years ago. In those findings, researchers discovered that treating people with elevated eye pressure could delay or prevent the onset of glaucoma. At that time, results for the subgroup of African Americans trended in the same direction, but were not conclusive.
Primary open-angle glaucoma affects about 2.2 million Americans age 40 and over, half of whom are not aware they have the disease. Vision loss from glaucoma occurs when the optic nerve is damaged. In most cases, elevated eye pressure, also called ocular hypertension, contributes to this damage. This causes gradual loss of peripheral (side) vision. As the disease progresses, the field of vision gradually narrows and blindness can result. Glaucoma has no early symptoms, and by the time people experience problems with their vision, they usually have a significant amount of optic nerve damage. However, if detected early, glaucoma can usually be controlled and serious vision loss prevented. Comprehensive dilated eye examinations are recommended at least once every two years for African Americans over age 40 and all people over age 60.
"This is the first study to recruit large numbers of African Americans to examine the benefit of pressure-lowering eye drops to prevent or delay the onset of glaucoma," said Paul A. Sieving, M.D., Ph.D., director of the NEI. "The results underscore that African Americans over age 40 should receive a comprehensive dilated eye exam at least once every two years to see if they are at higher risk for glaucoma."
These results do not imply that every African American with high eye pressure requires treatment, according to Eve Higginbotham, M.D., chair of the Department of Ophthalmology at the University of Maryland Medical Center and first author of the journal article. "When determining treatment, doctors should take into account several risk factors, including specific anatomical characteristics of the optic nerve and the cornea," Dr. Higginbotham said. "While African Americans participating in the study were more likely than others to have these specific physical characteristics, the study results underscore the importance of measuring these ocular risk factors rather than relying solely on the race or ethnicity of the individual."
Dr. Higginbotham suggested that before determining treatment, the doctor and patient should also discuss the patient's health status and life expectancy, and the burden of daily treatment, including cost, inconvenience, and possible side effects.
Elevated eye pressure results when the fluid that flows in and out of the eye drains too slowly, gradually increasing pressure inside the eye. It is estimated that between three and six million people in the U.S. are at increased risk for developing primary open-angle glaucoma, representing between four and seven percent of the population above age 40. In this study, ocular hypertension was defined as pressure of 24 mm Hg or greater in at least one eye.
The OHTS studied more than 1600 people, including 408 African Americans, 40-80 years of age who had elevated eye pressure but no signs of glaucoma. Half were assigned daily pressure-lowering eye drops, and the other half were assigned to observation (no medication). In the medication group, the number of African Americans participants developing glaucoma was significantly lower (8.4 percent) compared to the observation group (16.1 percent).
"The study also confirms that the risk for developing glaucoma is higher among African Americans compared with others," said Michael Kass, M.D., of the Washington University Department of Ophthalmology and Visual Sciences and chair of the study. "A number of risk factors may be contributing to the increased prevalence of visual impairment from glaucoma in African Americans. These include a family history of glaucoma; earlier onset of the disease compared to other races; later detection of the disease; and economic and social barriers to treatment."
Glaucoma is a leading cause of blindness in African Americans, said John Ruffin Ph.D., director of the NCMHD. "Glaucoma is almost three times as common in African Americans than Whites," Dr. Ruffin said. "However, if glaucoma is detected and treated early in its progression, it can usually be slowed and serious vision loss can be delayed."
Dr. Ruffin said Medicare covers an annual dilated eye examination for people at higher risk for glaucoma. This important preventive benefit defines higher risk as people with diabetes; those with a family history of glaucoma; and African Americans aged 50 and older.
In addition to support from the NEI and NCMHD, the Ocular Hypertension Treatment Study was supported by Research to Prevent Blindness and Merck Research Laboratories. The study was conducted at 22 clinical centers across the country. A list of study centers and principal investigators is attached.
The National Eye Institute (NEI), the Federal government's lead agency for vision research, is part of the National Institutes of Health (NIH) under the U.S. Department of Health and Human Services. NEI-supported research leads to sight-saving treatments and plays a key role in reducing visual impairment and blindness.
The NIH's National Center on Minority Health and Health Disparities (NCMHD) conducts and supports research, training, information dissemination and other programs aimed at reducing the disproportionately high incidence and prevalence of disease, burden of illness, and mortality experienced by certain American populations, including racial and ethnic minorities and other groups with disparate health status, such as the urban and rural poor.
Background
Ocular Hypertension Treatment Study (African-American Results)
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.
Ocular Hypertension Treatment Study
Current Principal Investigators & Study Centers
California
Anne L. Coleman, M.D., Ph.D.
Jules Stein Eye Institute, UCLA
Los Angeles
James D. Brandt, M.D.
University of California, Davis
Sacramento
Robert N. Weinreb, M.D.
University of California, San Diego
Michael V. Drake, M.D.
University of California, San Francisco
District of Columbia
Douglas E. Gaasterland, M.D.
University Ophthalmic Consultants of
Washington
Florida
Donald Budenz, M.D.
Bascom Palmer Eye Institute
University of Miami School of Medicine
Georgia
Thomas S. Harbin, Jr., M.D.
Eye Consultants of Atlanta
Allen D. Beck, M.D.
Emory University Eye Center, Atlanta
Kentucky
Joern B. Soltau, M.D.
University of Louisville
Maryland
Donald J. Zack, M.D., Ph.D.
The Johns Hopkins University School of Medicine, Baltimore
Michigan
Nauman R. Imami, M.D.
Henry Ford Medical Center, Detroit
Terry J. Bergstrom, M.D.
University of Michigan
W.K. Kellogg Eye Center, Ann Arbor
Bret A. Hughes, M.D.
Kresge Eye Institute
Wayne State University, Detroit
Minnesota
David C. Herman, M.D.
Mayo Clinic/Foundation, Rochester
Missouri
Edward M. Barnett, M.D., Ph.D.
Washington University School of Medicine
St. Louis
New York
Jeffrey M. Liebmann, M.D.
The New York Eye and Ear Infirmary
New York City
Ohio
Paul A. Weber, M.D.
Ohio State University, Columbus
Kathleen A. Lamping, M.D.
University Suburban Health Center
South Euclid
Oregon
George A. Cioffi, M.D.
Devers Eye Institute
Legacy Portland Hospitals, Portland
Pennsylvania
G. Richard Bennett, M.S., O.D.
Pennsylvania College of Optometry
Philadelphia
Jody R. Piltz-Seymour, M.D.
Scheie Eye Institute
University of Pennsylvania
Philadelphia
Texas
Ronald L. Gross, M.D.
Cullen Eye Institute
Baylor College of Medicine, Houston
Resource Centers
Study Chairman
Michael A. Kass, M.D.
Washington University
Dept. of Ophthalmology &Visual Sciences
660 South Euclid, Campus Box 8096
St. Louis, MO 63110
Telephone: (314) 362-5713
Vice Chairs
Dale K. Heuer, M.D.
Medical College of Wisconsin
Department of Ophthalmology
925 North 87th Street
Milwaukee, WI 53226-4812
Telephone: (414) 456-7915
Eve J. Higginbotham, M.D.
Maryland Center for Eye Care
Department of Ophthalmology
419 West Redwood, Room 580
Baltimore, M.D. 21201
Telephone: (410) 328-5929
Richard K. Parrish, II, M.D.
University of Miami
McKnight Vision Research Center, 5th Floor
1638 NW 10th Avenue
Miami, FL 33136
Telephone: (305) 326-6389
Coordinating Center
Mae O. Gordon, Ph.D.
Washington University
Dept. of Ophthalmology & Visual Sciences
Division of Biostatistics
660 South Euclid, Campus Box 8203
St. Louis, MO 63110
Telephone: (314) 362-3716
NEI Representative
Donald F. Everett, M.A.
National Eye Institute
National Institutes of Health
Suite 1300
5635 Fishers Lane, MSC 9300
Bethesda, MD 20892-7164
(301) 451-2020
Journal
Archives of Ophthalmology