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76 EW GLAUCOMA February 2011 September 2012 Tracking glaucoma among Asian ethnicities by Vanessa Caceres EyeWorld Contributing Writer Certain Asian populations are at a greater risk for the disease M ost glaucoma special- ists know that the Asian population is usually at higher risk for glaucoma. A study published in Ophthal- mology further pinpoints which Asian ethnic groups are at the great- est risk for which types of glaucoma. The study was led by Joshua D. Stein, M.D., Department of Oph- thalmology and Visual Sciences, University of Michigan, Ann Arbor. The study also shows a greater risk than previously thought for open-angle glaucoma (OAG) among the Asian-American population. "While it was once thought that open-angle glaucoma was relatively uncommon among individuals of Asian descent, in this study we were somewhat surprised to find that the risk of open-angle glaucoma among Asian Americans as a group was actually 50% higher than that of non-Hispanic whites," Dr. Stein said. Crunching the numbers Dr. Stein and co-investigators exam- ined data from approximately 2.25 million eyecare patients over the age of 40 who were enrolled in a man- aged-care network between 2001 and 2007. Patients had to have been in the analyzed database for more than a year and had to have one or more appointments with their eye- care provider. Investigators tracked the prevalence rates of OAG, narrow-angle glaucoma (NAG), and normal-tension glaucoma (NTG) ac- cording to race and Asian ethnicity. Statistical analyses comparing glaucoma rates against patients of different races were also performed. Investigators identified the race and ethnicity of each person in the study with the use of public records (specifically, drivers licenses) and a tool called E-Tech (Ethnic Technolo- gies, South Hackensack, N.J.) that assigns a race and ethnicity to the census block of that person's home address. Asian ethnicities included in the study were Chinese American, Filipino American, Indian American, Japanese American, Korean Ameri- can, Pakistani American, and Vietnamese American. There were not enough data to gather informa- tion on several other ethnicities, such as Bangladeshi, Thai, Indone- sian, and Sri Lankan, so they were grouped in an "Other" category. And the results? The study found the OAG preva- lence rate for Asian Americans was 6.52%, which was similar to that of Latinos (6.40%). That compared with a prevalence of 5.59% in non- Hispanic whites. Asian Americans also had a higher prevalence for NAG and NTG. "After adjustment for potential confounding factors, Asian Ameri- cans had a 51% increased hazard of OAG, a 123% increased hazard of NAG, and a 159% increased hazard of NTG compared with non- Hispanic whites," the investigators wrote. Eight-five percent (1.92 million) of patients in the study had a docu- mented ethnicity. Among those, the investigators were able to further track incidence and prevalence. The prevalence of OAG was highest in Japanese Americans (9.49%), second to Indian and Pakistani Americans (7.78% and 7.70%, respectively). Japanese Americans had a 3- to 10- times higher incidence of NTG than other Asian ethnicities. The preva- lence of NAG was highest among Chinese Americans (4.08%) and Vietnamese Americans (3.74%), percentages that were considerably higher compared with other Asian ethnicities. All Asian ethnicities had a higher prevalence of NAG compared with non-Asians. The actual reasons for the higher rates in some ethnicities are not clear, Dr. Stein said. "It may be due to genetic factors, environmen- tal factors, or other factors." Taking a closer look in the clinic This study sheds light on specific ethnic risk among the Asian popula- tion—the second fastest-growing mi- nority in the U.S.—versus classifying all Asian Americans in the same group, said Douglas J. Rhee, M.D., associate professor, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. These study results should push clinicians to more carefully consider patient backgrounds when deter- mining glaucoma risk, Dr. Stein said. "When ophthalmologists and optometrists evaluate Asian Ameri- cans, they should have a low thresh- old to perform gonioscopy to check the angle anatomy for narrow angles, especially in individuals of Chinese and Vietnamese ancestry," he said. Clinicians can also have a higher index of suspicion for NTG in Japanese Americans based on these results, he said. "Given the influx of Asian Americans over the past decade and projections that this group will con- tinue to grow in number over the coming years, as these individuals age, health policy makers will need to allocate additional resources in diagnosing and treating glaucoma in this patient population," Dr. Stein said. "With increasing numbers of these individuals in the United States, it is important that ophthal- mologists apply different risk assess- ments than we generally use for primary open-angle glaucoma, which is more prevalent in the U.S. Caucasian population," said Louis B. Cantor, M.D., chairman and professor of ophthalmology, Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis. Refractive error, axial length, and other factors may be more im- portant to consider with angle-clo- sure glaucoma risk, Dr. Cantor said. The decision to purchase and use certain tools for glaucoma detec- tion based on these kinds of studies should be considered not only in the U.S. but also in Asian countries, said Shan Lin, M.D., professor of oph- thalmology, Department of Oph- thalmology, University of California, San Francisco. For example, the scanning peripheral anterior cham- ber depth analyzer for angle-closure glaucoma is more prevalent in Asia, which makes sense when you con- sider the higher risk of this glau- coma type among Asians, he said. Although Dr. Rhee believes that glaucoma prevalence in the Asian population is now well established, he thinks this kind of study paves the way for genetic profiling within glaucoma. "In the distant future, we may be able to attribute risk to the presence or absence of certain genetic profiles," he said. Dr. Lin agreed that genetic pro- filing and research is an area ripe for exploration. He also believes that a closer look at risk in Asian ethnici- ties that could not be covered in this study would be another future research area. Although Dr. Lin believes the ethnicity classification method used in the study is a weakness, he said it does not detract from the overall value of the study results. Dr. Stein and co-investigators are conducting research regarding whether racial disparities exist in how eyecare providers care for glaucoma patients. EW Editors' note: The physicians have no financial interests related to this article. Contact information Cantor: 317-274-8485, lcantor@iupui.edu Lin: Lins@vision.ucsf.edu Rhee: 617-573-3670, douglas_rhee@meei.harvard.edu Stein: jdstein@med.umich.edu