Longitudinal change of refractive error in infants during the first year of life.

Using cycloplegia, the change in ametropia of 113 infants was followed at 3 month intervals over the first year of life. Scatterplots of the spherical equivalent power show that the dioptric differences exhibit a significant myopic shift of -0.38 ds between 26 and 36 weeks and -0.38 ds between 36 and 52 weeks. The spread of the dioptric differences (95% CI) does not appear to be related to the magnitude of the ametropia present and decreases with time. By 12 months of age the frequency distribution of the spherical equivalent appears to become leptokurtic as it is in the adult. On average the astigmatism was of low degree (less than 1 dioptre cylinder) and with the rule. Anisometropia was rarely seen. The results of this longitudinal study point to an optimal time for screening and perhaps prescribing for 'abnormal' refractive error between 9 and 12 months of age.