Abstract
A method is described for the measurement of the radii of corneal curvature in the vertical and horizontal meridians. It was applied to the study of the change in curvature during the convergence of the ocular axes from an approximately primary position to a binocular fixation spot situated at some 5 metre-angles: (a) the eye under test remaining in the primary position, and (b) when such a fixation spot was placed in the sagittal plane through the head. The subjects were divided into three age-groups: (i) between 8–15 years old; (ii) adult nonpresbyopes; (iii) presbyopes. Group (ii) was studied when the eye under test remained in the primary position and no change in curvature was detected following convergence. All three groups were studied in situation (b) and Groups (i) and (ii) showed a statistically significant increase in the horizontal radius of curvature following convergence. The data are related to others on senile changes in corneal astigmatism. They are not found to be compatible with Hering's Law.
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