The principle of treating intermittent esotropia is to create conditions that will allow the patient to have comfortable and functionally complete binocular vision depending on the individual case, a symptomatic esophoric patient in whom refraction reveals a significant amount of hypermetropia (at least
1.25D sph) is treated by full correction of the hypermetropic refractive error in the same manner as in an esotropic patient. Surgery should be considered only when the size of the deviation in a patient with intermittent esotropia falls within the range that can be corrected without fear of overcorrection. Prerequisites for planning surgery are stability of the deviation after full correction of the hypermetropic refractive error and the presence of muscular asthenopia. When the decision has been made to operate, the surgeon should determine the extent of surgery necessary and select the muscles to be operated on. Many surgeon believe thant patients with intermittent deviations need lesser amounts of surgery. This attitude is erroneous, of course, and causes undercorrections that, because of their small size, may be difficult to control by additional surgery. The rule is : The amount of surgery must be aimed at the basic deviation and on the goal to align the eyes, regardless of whether it is a latent, intermittent, or manifest deviation. It is preferable to establish a secondary exophoria rather than be left with a residual esophoria. Convergence fusional movements and also voluntary convergence are more effective than the divergence mechanism in keeping such a residual heterophoria in check. In younger patients, small surgical overcorrections present no problem and usually are easily compensated for by fusional convergence. On the other hand, a consecutive exodeviation, regardless of how small, can cause considerable and often insurmountable difficulties.