Distribution of ocular biometric parameters and refraction in a population-based study of Australian children

PURPOSE. To study the distribution of spherical equivalent refraction and ocular biometric parameters in a young Australian population. METHODS. Noncontact methods were used to examine ocular dimensions and cycloplegic autorefraction in a stratified random cluster sample of year 1 Sydney school students (n = 1765), mean age 6.7 years (range, 5.5-8.4 years). Repeated measures of axial length, anterior chamber depth, and greatest and least corneal radius of curvature (CR1, CR2, respectively) were taken in each eye. Refraction was measured as the spherical equivalent. RESULTS. Mean spherical equivalent refraction in right eyes was + 1.26 ± 0.03 D (SEM; range, -4.88 to +8.58). The distribution was peaked (kurtosis 14.4) and slightly skewed to the right (skewness, 1.7). Prevalence of myopia, defined as spherical equivalent refraction ≤ -0.5 D, was 1.43% (95% CI, 0.94-2.18) in the overall population. Axial length, anterior chamber depth, and corneal radii of curvature were normally distributed. The mean axial length in right eyes was 22.61 ± 0.02 mm (SEM; range, 19.64-25.35). The mean anterior chamber depth was 3.34 ± 0.01 mm (SEM; range, 2.14-4.06). Mean CR1 was 7.85 ± 0.01 mm (SEM) and mean CR2 was 7.71 ± 0.01 mm (SEM). The distribution of axial length/mean corneal radius ratio was peaked (leptokurtic) with a mean of 2.906. Mean axial length was longer, anterior chambers were deeper, and corneas were flatter in the boys. CONCLUSIONS. A peaked (leptokurtic) distribution of spherical equivalent refraction was present in this predominantly hyperopic 6-year-old population. The results also showed that ocular biometric measures were normally distributed, with statistically significant gender differences found in measurements.