Reduction of astigmatism after infancy in children who did and did not wear glasses and have strabismus.

The purpose of this study was to record and explain the changes in astigmatism as normal and strabismic infants grew. Two-hundred-and-eighty-nine hypermetropic infants were randomly allocated to wear glasses from the age of six months. Changes in astigmatism and in hypermetropia of the horizontal and vertical meridia were compared in those who did and did not wear glasses and have strabismus. Mean astigmatism decreased significantly (p < 0.001) in both eyes of normal and strabismic children, but the 'last' astigmatism was significantly (p < 0.001) larger in both eyes of those who had strabismus. There was a similar progressive decrease of hypermetropia in both meridia of both eyes within each diagnostic group, but with the exception of the vertical meridian of the non-fixating eyes (in which the difference approached statistical significance), this was significantly (p < 0.01) larger in the normal children. The consistent wear of glasses was not associated with change in both meridia of both eyes in the normal children (p < 0.005), but had no significant effect on the changes in astigmatism. Since the changes in the two meridia were proportional to the starting level, hypermetropia decreased more in the meridian which was, initially, the more hypermetropic one, and the difference between them, i.e. astigmatism, tended to disappear whether or not the child eventually had strabismus.