Evidence of Effect of Day Length Factor on Infantile Refractive Development: Multiple Regression Analysis-based...

Purpose: As the relationships between refraction and birth month suggest that day length factors affect the infantile refractive development, we aimed to prove the effect of day length factors by examining its evidence even among the elderly. Methods: We studied 1622 patients with cataracts (740 men and 882 women) who had preparatory measurements for corneal radius, axial lengths, and refractions for intraocular lens implantation. The day lengths for which each subject was exposed to from the first to eleventh month since birth were represented by variables DL1 to DL11. Similarly, absolute deviations from the yearly average of day lengths were represented by DDL1 to DDL11. We performed multiple regression analysis by substituting DL or DDL as explanatory variables for corneal radius, axial length, or refraction. Results: DLs were not relevant variables in elucidating corneal radius, axial length, and refraction. In contrast, DDLs were relevant variables in elucidating corneal radius (p<0.05). This association weakened for refraction and was not pertinent for axial length. Conclusion: Infantile refractive development is affected by the deviation in day length rather than the day length itself, evidence for which can still be observed among the elderly.