Variability of strabismus surgery for acquired esotropia.

We developed a mathematical model to predict the probable success rate of the first surgery to correct acquired esotropia with normal accommodative convergence-accommodation ratio in children. A computer-averaged dose-response curve of the effect of 68 bilateral medial rectus recessions was combined with various assumptions regarding likely errors in surgical performance and likely errors in measurement of the preoperative deviation. Fifteen different sets of reasonable assumptions were tested, giving a range of theoretical success rates from 72% to 96%. The results of this study clearly indicate that a certain proportion of failures is to be expected when this or other forms of strabismus are treated surgically by a fully competent ophthalmic surgeon performing as accurately as is practically possible.