Purpose: To find which kind of light exposure and what sensitivity patterns in infancy influence the relationship between ocular refraction and birth month.
Methods: We studied 13,757 children whose cycloplegic refraction could be tested during their initial visit to a children's hospital. After dividing subjects into four groups based on refractive degree, the risk ratio for each birth month was calculated from the cases for that month and the results were adjusted using the national birth/month. We then inversely assessed the risk ratio according to the birth month in each group using simply modeling matrix equations.
Results: When results were calculated based on the possible effect of the day length, there was a wide variation in the degree of sensitivity depending on the number of months passed since birth at time of investigation, the statistical results falling into insignificant bimodal peaks. In contrast, when based on the assumption the effect was associated with deviations from the yearly average of the day length, far less variation was observed and there was a single natural sensitivity peak at around five months of age in all four refractive groups.
Conclusion: Assuming that the peak stage of influence deviation from the yearly average of the day length has on the infant's refraction is at five month, there is a relationship between the refractive degree and the month of birth.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 120: 533-539, 2016.