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R. E. Manny, L. Dong, J. E. Gwiazda, L. Hyman, K. D. Fern, W. L. Marsh-Tootle, K. Weise, COMET/COSMICC Study Group; Intraocular Pressure (IOP) and Central Corneal Thickness (CCT) in the Collaborative Observational Study of Myopia in the COMET Cohort (COSMICC). Invest. Ophthalmol. Vis. Sci. 2010;51(13):2196.
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To investigate associations between IOP and CCT with age, gender, ethnicity and refractive error in myopic young adults.
In year 11 of COSMICC, IOP (Goldmann) and CCT (Pachmate DGH55) measurements were introduced and obtained pre-dilation on 370 of the original 469 cohort (age range: 17 to 23 years). Potential covariates of interest (age, gender, ethnicity and cycloplegic autorefraction [Nidek ARK 700A]) were analyzed by ANOVA for the right eye and 2-sample t-tests used for comparison within subgroups.
Mean IOP (mm Hg) was 15.1±3.0 and did not vary by gender, age or magnitude of myopia but differed by ethnicity (p=0.002) with IOP of African-Americans (n=104, 15.9±3.3) significantly higher than Hispanics (n=53, 13.8±2.6, p<0.0001) and Whites (n=162, 15.1±2.8, p=0.03) but not Asians or mixed ethnicity. Mean CCT(µm) was 561.8±36.3 and did not vary by gender, age or magnitude of myopia but differed by ethnicity with CCT of African-Americans (mean 554.8±40.3) thinner than Asians (570.2±35.1, p=0.04) and Whites (564.8±32.1, p=0.03) but not Hispanics or mixed ethnicity. A modest positive correlation (r=0.23, p<0.001) was found between IOP and CCT. This correlation also varied by ethnicity with the highest correlation in Asians (r=0.52, p=0.003) and lowest in Mixed and Hispanic (r=0.20, not significant). IOP also varied by CCT categories (p<0.0001) with significant differences found between the 1st quartile (CCT<537, mean IOP 14.2±3.1) and 3rd quartile (CCT 560.4 to 586, mean IOP 15.1±2.6, p=0.03) and between the 1st quartile and 4th quartile (CCT>586, mean IOP 16.2±3.3, p< 0.001).
Myopic young adults showed small but significant differences in IOP and CCT by ethnicity but not by age, gender or magnitude of myopia. Higher IOP coupled with thinner corneas in African-Americans suggests that measured IOP underestimates IOP in this group and may have implications for earlier routine assessment of IOP and CCT in African-Americans.
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