It's generally known that African Americans have the highest risk for glaucoma (about 12 percent) among racial groups in the United States. They are more than twice as likely as non-Hispanic white Americans (5.6 percent) to develop this potentially blinding disease. But little was known about risks for Asian Americans until a National Eye Institute funded study published recently in Ophthalmology journal (online). By reviewing insurance records of more than 44,000 Asian Americans older than 40, the researchers found their glaucoma risk to be 6.5 percent, which is about the same as U.S. Latinos.

Racial-ethnicity risk rates help people and doctors plan for eye care and take extra precautions if appropriate. Since Asian Americans are the second fastest growing population in the U.S.– a trend likely to continue for years to come– such risk information is urgently needed.

The study also detailed the Asian American ethnic groups most likely to develop the three main types of glaucoma: open-angle (OAG, the most common form), narrow-angle (NAG), and normal-tension (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 in the eye; the patient usually feels severe, rapid-onset pain and needs immediate treatment to prevent vision damage. The risk of NTG was three to 10 times higher in Japanese Americans than other Asian ethnicities studied, and nearly all of the Asian sub-groups were at higher risk than non-Asian Americans. With NTG, the optic nerve and vision sustain damage even though the pressure within the eye remains within "normal" levels. Among Asian Americans, OAG rates were highest among Japanese Americans (about 9.5 percent), followed by Indian and Pakistani Americans (about 7.7 percent).

The study was led by Joshua D. Stein, MD, Kellogg Eye Center, University of Michigan, who said the results have implications for patient care.

"For example, the inner eye angle anatomy of patients of Chinese or Vietnamese ancestry should be carefully examined," Dr. Stein said. "And since NTG won't be detected by simply measuring intraocular pressure (IOP), eye doctors need to assess the status of the optic nerve in patients whose ethnicity makes them more susceptible to this type of glaucoma," he added. He and his coauthors recommend that future studies explore potential genetic and environmental reasons for some of the observed differences in glaucoma rates among the different races and Asian ethnicities.