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Changes in ocular axial dimensions and refraction were followed longitudinally, using ultrasonography and retinoscopy, during the first year of life (mean ages 4-53 weeks) of a group of 20 full-term infants (10 male, 10 female). Using a mixed-model regression analysis, axial length changes as a function of time were found to be best described by a quadratic expression (AL=17.190+0.128x-0.0013x(2), where AL is the axial length in mm and x is the age in weeks), while anterior chamber depth changed linearly (ACD=2.619+0.018x, where ACD is the anterior chamber depth in mm): lens thickness was essentially constant. Spherical equivalent refraction through most of the first year showed a steady reduction in hypermetropia (SER=2.982-0.032x, where SER is the spherical equivalent refraction in dioptres): astigmatism also tended to diminish. Mean hyperopic refractive errors through the year were negatively correlated with corresponding axial lengths (SER=12.583-0.541AL), but some individual subjects showed marked departures from this pattern. These results are discussed in relation to concepts of emmetropization.

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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.