Study finds increased risk for glaucoma in Asian Americans
Joshua D. Stein, M.D., M.S., a glaucoma specialist at the U-M Kellogg Eye Center
Increased cupping of the optic nerve and thinning of the neuroretinal
While it's generally known that African Americans have the highest risk for glaucoma, a new study reports that Asian Americans face a significantly increased risk of developing glaucoma, a potentially blinding disease.
Joshua D. Stein, M.D., M.S., a glaucoma specialist at the U-M Kellogg Eye Center, reviewed claims data of more than 44,000 Asian Americans over age 40 who were enrolled in a nationwide managed care network. He found Asian Americans' risk for open-angle glaucoma to be 51% higher than that of non-Hispanic whites.
Glaucoma is a condition that affects the optic nerve, the structure responsible for transmitting visual information from the eye to the brain so it can be processed and interpreted. Damage to the optic nerve results in progressive loss of peripheral vision and, if left untreated, can lead to irreversible blindness.
Glaucoma is the second most common cause of blindness worldwide and, in the United States, over two million people and almost two percent of all adults over age 40 have glaucoma.
The study, published in June in Ophthalmology, has implications for eye doctors, says Stein, who notes that Asian Americans are the second fastest growing population in the U.S.
"Clinicians should be aware that their Asian American patients are at increased risk for glaucoma and should monitor them for signs of the disease," he says.
Stein explains, "Most forms of glaucoma are asymptomatic early in the course of the disease. Individuals who have risk factors for glaucoma -- older age, nonwhite race, and a family history of glaucoma -- should have routine eye exams for the disease. This exam includes checking intraocular pressure, examining the optic nerve and, when appropriate, performing visual field testing to detect loss of peripheral vision, a key sign of glaucoma."
The study detailed the Asian American ethnic groups most likely to develop the three main types of glaucoma: open-angle glaucoma (OAG, the most common form), narrow-angle glaucoma (NAG), and normal-tension glaucoma (NTG).
The rate of NAG was higher in Asian Americans than in any other racial group in the study and highest of all among Chinese and Vietnamese Americans. With NAG, the part of the eye that drains excess fluid becomes blocked and pressure builds up. The patient usually feels severe, rapid onset pain and needs immediate treatment to prevent vision loss.
The risk of NTG was 3 to 10 times higher in Japanese Americans than other Asian ethnicities and nearly all of the Asian subgroups were at higher risk than non-Asian Americans. With NTG, the optic nerve sustains damage even though eye pressure remains within "normal" levels.
Eye doctors should look for signs of glaucoma when evaluating Asian American patients over age 40. "For example, the inner eye angle anatomy of patients of Chinese or Vietnamese ancestry should be carefully examined," Stein says.
"And since NTG won't be detected by simply measuring intraocular pressure, eye doctors need to assess the optic nerve and, when appropriate, perform visual field testing in patients whose ethnicity makes them more susceptible to this type of glaucoma," he adds.
FOR MORE INFORMATION
Reference: Volume 118, Issue 6, Pages 1031-1037, June 2011 Glaucoma, Cataract, and Anterior Segment Disease: www.kellogg.umich.edu/ patientcare/glaucoma.service.html
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