Does the month of birth influence the prevalence of refractive errors?

Purpose: The aim of our study was to examine whether the month of birth influences the prevalence of refractive errors.

Material And Methods: A total of 5,601 schoolchildren were examined (2,688 boys and 2,913 girls, aged 6-18 years, mean age 11.9, SD 3.2 years). The children examined, students of elementary and secondary schools, were Polish and resided in and around Szczecin, Poland. Every examined subject underwent retinoscopy under cycloplegia using 1% tropicamide. Data analysis was performed using the Kruskal-Wallis test followed by the Siegel and Castellan post-hoc test or the Mann-Whitney U-test. P values of < 0.05 were considered statistically significant.

Results: Students born in June had significantly higher spherical equivalents than schoolchildren born in May (0.66 ± 1.17 and 0.39 ± 1.17 respectively, p = 0.0058). The Mann-Whitney U-test showed that students born in June had significantly higher spherical equivalents than schoolchildren born in any other month (0.66 ± 1.17 and 0.50 ± 1.17 respectively, p = 0.0033). Besides that, we did not observe any other association between refractive errors and the month of birth.

Conclusion: Children born in Poland in June may have a higher spherical equivalent.