COLUMBUS, Ohio — The Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study reported that there are marked differences in refractive error and ocular dimensions of children in various ethnic groups.
Researchers examined children in grades 1 through 8 during the 1997-1998 academic year at four clinical sites: West Alabama Health Services, Eutaw, Ala.; University of Houston College of Optometry; University of California, Berkeley School of Optometry and Southern California College of Optometry. While recruitment is ongoing, last year’s results included approximately 500 children each from three of the four ethnic groups studied — African American, Hispanic and Asian — and more than 1,000 Caucasian children. Refractive error, axial length and corneal curvature were measured in all of the participants.
Researchers found the highest prevalence of myopia, defined as - 0.75 D or more, among Asians, at 17.3%, followed by Hispanics at 14.1%, African-Americans at 6.6% and Caucasians at 4.5%. Axial length and corneal curvature also varied depending upon ethnic group.
The study, sponsored by the National Eye Institute, was initiated in 1997 by a team of researchers led by Karla Zadnik, OD, PhD, from the Ohio State University College of Optometry. Study results are being presented this month at the annual meeting of the Association for Research in Vision and Ophthalmology.
The primary outcome measure for refractive error, considered to be the most important, is cycloplegic autorefraction. The children get two drops of a cycloplegic. The actual drop type varies depending on eye color. The measurement itself is then taken with a Canon R1 autorefractor, a device that is no longer manufactured but is an “ideal autorefractor to use on children,” Dr. Zadnik told Primary Care Optometry News.
The second most important measurement that is taken is the axial dimensions of the eye. A-scan ultrasonography is useful for generating biometric measurements of this type. Dr. Zadnik said that five ultrasound readings of the overall length of the eye, the depth of the anterior chamber and the thickness of the crystalline lens can be taken on a child as young as 6, almost as fast as the ultrasound readings can be taken.
“Some of the results were surprising,” Dr. Zadnik said. “For example, the prevalence of myopia does not quite fall out like we expected, but overall we really did expect to find some ethnic group-related difference.”
The CLEERE Study was expanded from the Orinda Longitudinal Study for Myopia, which began about 10 years ago. That study, however, consists predominantly of Caucasian participants.
“This is the first one to try to use the exact same methods at the same point in time on different ethnic groups,” Dr. Zadnik said.
For Your Information:
- Karla Zadnik, OD, PhD, can be reached at the Ohio State University College of Optometry, 338 West 10th Ave., Columbus, OH 43210-1240; (614) 292-6603; fax: (614) 292-4705; e-mail: email@example.com.