Photorefractive measurements of astigmatism in infants and young children.

We have photorefracted 312 infants and young children in Tompkins county in New York state and characterized the magnitude and axes of their astigmatisms. The population was solicited by letter from birth announcements or photographed at nursery schools, and was composed of children free of ocular problems. As had been previously reported, we found that the prevalence of astigmatisms of greater than 1 diopter decreased with increasing age. Roughly 7 of 10 infants aged 1 year of younger had one eye with at least 1 diopter of astigmatism or more, while only 1 out of 10 children of age four or more had an eye with 1 or more diopters of astigmatism. A longitudinal study of 26 infants also showed a decrease in the amount of astigmatism over the first three years of life. In infants up to 2 years of age from Tompkins County, the ratio of against-the-rule:oblique:with-the-rule astigmatisms was 15:9:1 in the most astigmatic eye. Generally the axes of oblique astigmatism showed bilateral symmetry. Photorefraction of a group of 159 infants from the city of Seattle showed a similar prevalence of astigmatism, but a slightly different ratio of kinds of astigmatism.