Inter-Racial Differences in Axial Length of Young Singaporean Males

PURPOSE: To establish a database of axial length for young Singaporean males and define inter-racial differences. METHODS: This retrospective study included 897 eyes of 459 healthy males (17.50 ± 1.14 years old) without a history of eye disease or myopia control treatments. Subjects were emmetropes or myopes with visual acuity 6/6. Demographics and non-cycloplegic auto-refraction data were collected. AL and cornea radius of curvature (r1, r2) were measured using an IOLMaster 500, with the latter converted to average keratometry in Dioptres. Participants were grouped based on race (Chinese, Malay, and Indian) and spherical equivalence (emmetropia to ≤-7D, stratified into 5 subgroups). Linear mixed models were used to account for inter-eye correlation, and the effect of race within each subgroup was assessed using Type III F-tests. Post hoc Tukey's pairwise comparisons were applied when indicated. RESULTS: The Chinese had grossly higher AL across all subgroups, but statistical significance was only reported in the moderate myopia group (-3D to -5D). The Indians had significantly higher mean keratometry power across the -1D to -7D myopia range. Percentile charts were plotted to demonstrate the spread of AL for emmetropes and across different refractive error subgroups. High AL of 26 mm was observed 1% of emmetropes and 25% of moderate myopes. CONCLUSION: This database for AL may supplement existing age-specific percentile charts for AL to risk-stratify myopic patients. Abnormally high AL (26 mm) was observed in low to moderate myopes, predisposing them to myopic complications. Myopia management and screening should therefore have greater emphasis on AL measurements, in addition to refraction.