Surgical correction of convergent strabismus: its relationship to prism compensation

Esotropic patients whose angle of strabismus has been corrected by prisms frequently increase their angle deviation to compensate for the prismatic correction. This sensorio-motorial reaction to prism correction has been given the name of anomalous movements (a.m.). Quantification of a.m. has been made according to the amount of prisms that an esotropic patient is capable of compensating for (progressive prism compensation test--p.p. test). Some esodeviation does not compensate for any prisms at all since a.m. have not yet developed. Other cases compensate for as much as 40 or 60 prism diopters and more of over-correction of the angle deviation and they therefore have powerful a.m. The interference of these innervational forces acting on the medial recti to corrective surgery has been studied in 126 operated esotropic patients. A significant decrease from the expected surgical result (p less than 0.001) has been found in patients having powerful a.m., as can be judged by the p.p. test. It is believed that a.m. are an important drawback contributing to vitiate any formula on the amount of muscle surgery to be performed in patients having no possibilities of restoring normal binocular vision. Practical advice on how to eliminate this drawback and theoretical reasoning on the significance of a.m. are offered.