Distribution of Ocular Biometry in 7-and 14-Year-Old Chinese Children

Purpose. To describe distributions of ocular biometry and their associations with refraction in 7- and 14-year-old children in urban areas of Anyang, central China. Methods. A total of 2271 grade 1 students aged 7.1 +/- 0.4 years and 1786 grade 8 students aged 13.7 +/- 0.5 years were measured with ocular biometry and cycloplegic refraction. A parental myopia questionnaire was administered to parents. Results. Mean axial length, anterior chamber depth, lens thickness, central corneal thickness, corneal diameter, corneal radius of curvature, axial length/corneal radius of curvature ratio, and spherical equivalent refraction were 22.72 +/- 0.76 mm, 2.89 +/- 0.24 mm, 3.61 +/- 0.19 mm, 540.5 +/- 31 mu m, 12.06 +/- 0.44 mm, 7.80 +/- 0.25 mm, 2.91 +/- 0.08, and + 0.95 +/- 1.05 diopters (D), respectively, in 7-year-old children. They were 24.39 +/- 1.13 mm, 3.42 +/- 0.41 mm, 3.18 +/- 0.24 mm, 548.9 +/- 33 mu m, 12.03 +/- 0.43 mm, 7.80 +/- 0.26 mm, 3.13 +/- 0.14, and j2.06 +/- 2.20 D, respectively, in 14-year-old children. Compared with 7-year-old children, the older group had significantly more myopia (-3.0 D), longer axial length (1.7 mu m), deeper anterior chamber depth (0.3 mm), thinner lens thickness (-0.2 mm), thicker central corneal thickness (10 mu m), and greater axial length/corneal radius of curvature ratio (0.22) (all p < 0.001), as well as smaller corneal diameter (-0.03 mm, p = 0.02) and similar corneal radius of curvature. Sex differences were similar in both age groups, with boys having longer axial length (0.5 mm), deeper anterior chamber depth (0.1 mm), shorter lens thickness (0.03 mm), greater central corneal thickness (5 mu m), greater corneal diameter (0.15 mm), and greater corneal radius of curvature (0.14mm) than girls (all p = 0.01). The most important variables related to spherical equivalent refraction were vitreous length, corneal radius of curvature, and lens thickness. Conclusions. The 14-year-old group had larger parameter dimensions than the 7-year-old group except for corneal radius of curvature (unchanged) and lens thickness and corneal diameter (both smaller). Boys had large parameter dimensions than girls except for lens thickness (smaller). Axial length, corneal radius of curvature, and lens thickness were the most important determinants of refraction.