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Abstract
The distribution of refractive errors was followed in chicks from hatching to 8 weeks of age. A dramatic progressive decrease in the variability of refractions was observed over this period. In addition, there appeared to be a parallel decline in hyperopia, even when the artifactual hyperopia of retinoscopy was taken into account. These results are evidence for a postnatal development regulatory mechanisms, most likely dependent on vision, which directs growth of the eye toward emmetropia.