Variation of the contribution from axial length and other oculometric parameters to refraction by age and ethnicity.

PURPOSE To compare the distribution of spherical equivalent refraction (SER) and other ocular parameters and to assess the contribution from oculometric parameters to SER in two age-specific, cross-sectional samples of children, and in two ethnic groups (European Caucasian and East Asian). METHODS A random-cluster design was used to recruit predominantly 6-year-old (1765 participants, 78.9% response) and 12-year-old children (2353 participants, 75.3% response) from schools across Sydney, Australia. Data collection included questionnaires and eye examination (keratometry, biometry, and cycloplegic autorefraction). Results of three analytical methods (Pearson correlation, partial correlation coefficient, and linear regression analyses) are reported for 6- and 12-year-old children. RESULTS Kurtosis for SER and axial length (AL) in the 12-year-old children (14.3 and 2.1, respectively) was similar to that previously reported for the 6-year-old children (11.3 and 0.5). AL showed high correlation (r) with SER in the 6- (r = -0.44) and 12-year-old (r = -0.61) children. Lower correlations for SER with corneal radius (r </= 0.09) and with lens power (r </= 0.13) were noted in both samples. In multivariate models, AL accounted for 24% and 49% of the variations in SER for the 6- and 12-year-old children, respectively. In these older children, correlations between AL and SER were greater in the East-Asian ethnic group (r = -0.79 vs. -0.47), and multivariate analyses showed that AL accounted for a greater proportion of the variation in refraction in East-Asian children (68%) than in European-Caucasian children (24%). CONCLUSIONS In the samples of predominantly 6- and 12-year-old children, the main determinant of SER was AL. The greater contribution of AL in the older sample and in East-Asian children corresponds well with recently proposed models of continuing axial elongation in the absence of compensatory lens changes.