Management of acquired esotropia.

The aetiology of accommodative esotropia is hypermetropia and a high ratio of accommodative convergence to accommodation (the AC/A ratio). In a study conducted by me many years ago, the patients with accommodative esotropia were divided into those with normal AC/A and high AC/A ratios. The average hypermetropia among the former was + 4-75 D sph. in the least of the two farsighted eyes as determined by the spherical equivalent. Among the latter, the average hypermetropia was + 2'25 D sph. The patients with a normal AC/A ratio have approximately the same prism and alternate cover measurements for both distance and near, whereas those with a high AC/A ratio have greater esotropia for near than distance. The hereditary aspect of accommodative esotropia is well documented. The aetiology of both the hypermetropia and the high AC/A ratio shows the classic genetic pattern of dominant inheritance with a variable expressivity and penetrance. The average age at onset of accommodative esotropia is 2j years. I have personally documented congenital esotropia as early as 6 months and as late as 7 years. Characteristically, the esotropia is intermittent at onset, but the tendency is for the frequency and duration of the esotropia to increase, and constant esotropia gradually replaces the intermittent pattern. After a variable period of constant esotropia, the added complication of a non-accommodative component becomes manifest by a residual esotropia persisting after all accommodation has been inactivated. The ideal management of accommodative esotropia is one that permits the institution of anti-accommodative therapy while the esotropia is still intermittent. Since accommodative esotropia begins in childhood and the aetiological factors persist, long-range antiaccommodative therapy is required. Surgery cannot be successfully substituted for antiaccommodative therapy. The specific anti-accommodation therapies available are: plus lenses and miotics.