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Elise Noel Harb, Leslie Hyman, Jane E Gwiazda, Wendy Marsh-Tootle, Qinghua Zhang, Wei Hou, Thomas T Norton, Keri Dirkes, Linda M Zangwill, COMET Study Group; Choroidal thickness profiles in myopic eyes of young adults in the Correction of Myopia Evaluation Trial cohort. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3634.
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To examine the relationship of choroidal thickness (ChT) with axial length (AL) and myopia in young adult eyes in the large, ethnically diverse COMET cohort.
COMET, initially a myopia treatment trial, enrolled 469 myopic children and had 14 years of follow-up. At their last visit (mean age of 24.3±1.4 years), in addition to measures of myopia by cycloplegic autorefraction and AL by A-scan ultrasonography, participants underwent OCT imaging of the choroid (RTVue) in both eyes. Using digital calipers, two independent readers manually measured ChT in the right eye (left eye if poor right eye quality (n=37)) at seven locations; fovea and 750, 1500, 2250μm nasal (N) and temporal (T) to the fovea. The average of the two ChT measures was used, after adjudication for any discrepant measurements.
ChT measurements were available from 294/346 (85%) imaged COMET participants (44.9% male), with mean myopia of -5.3±2.0D and mean AL of 25.5±1.0mm. Overall, ChT varied by location (p<0.0001) and was thickest at the fovea (273.8±70.9μm) and thinnest in the nasal periphery (N2250, 191.5±69.3μm). Univariate analysis, based on a median split (4.94D of myopia / 25.49mm AL), showed thinning of ChT in longer or more myopic eyes at all locations (p≤0.02), but was most notable in the nasal locations (~35μm thinner in longer or more myopic eyes, p<0.01). Compared to African-Americans, Asians had significantly thinner ChT (~35-66μm thinner) in all locations except T1500 and T2250 (p≤0.02). At N1500 and N2250, Caucasians and Hispanics also had thinner ChT compared to African-Americans (p≤0.05). There was no significant difference in ChT by gender at any location. After adjusting for ethnicity and age (using AL or myopia as a covariate) thinner ChT remained associated with more myopia or longer AL at all locations (p≤0.03) and ChT was associated with ethnicity in some, but not all locations.
Choroids were thinner in eyes with more myopia or longer AL in the ethnically diverse COMET cohort. In some locations, ethnicity was associated with choroidal thickness, with Asians having the thinnest choroids. Longitudinal human studies are needed to determine how the choroid changes during the axial elongation associated with myopia.
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