Factors associated with macular thickness in the COMET myopic cohort

To determine whether macular thickness is associated with ethnicity, gender, axial length (AL), and severity of myopia in a cohort of young adults from the Correction of Myopia Evaluation Trial (COMET).

Eleven years after their baseline visit, 387/469 (83%) subjects returned for their annual visit. In addition to the protocol-specific measures of spherical equivalent refractive error (SER) and AL, high-resolution macular imaging also was performed with optical coherence tomography (RTVue). From these scans, full-thickness values for the central (1 mm), parafoveal (1 to 3 mm), and perifoveal (3 to 5 mm) annular regions were calculated. Gender, ethnicity, AL, and SER were examined for associations with macular thickness using univariate and multivariable linear regression analyses.

In the 377 subjects with usable data (mean age = 21.0 ± 1.3 years), the mean SER ± SD was -5.0 ± 1.9 D and mean AL was 25.4 ± 0.9 mm. Mean foveal thickness was 252.0 ± 20.1 microm in the center, 315.6 ± 14.0 microm in the parafovea, and 284.4 ± 12.9 microm in the perifovea. In the best-fit multivariable model that adjusted for gender, ethnicity, and AL, females had significantly thinner maculas than males for all three regions (p < 0.0001), with the largest difference in the center (12.8 microm, 95% confidence interval: 9.2 to 16.4). The effect of ethnicity was strongest in the central fovea, with African-Americans, Asians, Hispanics, and mixed ethnic groups having thinner maculas than whites (all p values < 0.005). Increased AL was significantly associated with slightly thicker central foveas (p = 0.001) and thinner parafoveal (p = 0.02) and perifoveal (p < 0.0001) regions.

In this ethnically diverse cohort of moderate and high myopes, females and African-Americans were found to have the thinnest central foveas. Whether such thinning in the macula as a young adult is a risk factor for future disease remains to be determined.