We performed a prospective study of preoperative prism adaptation in 77 patients with acquired esotropia. Sixty-three of them increased their angle of squint when wearing Fresnel press-on prisms for 5-7 days. After the angle had stabilized to a point that did not exceed the press-on prisms by more than 10 prism D, they were randomly divided into two groups. Thirty-two patients underwent surgery based on the prism-adapted angle. The other 31 patients underwent surgery based on their initially measured angle. Fourteen patients who did not respond to prism correction underwent surgery based on the angle before prism correction. Success rates with deviations between 0 and 10 prism diopters measured 1 year after surgery were highest in those in whom surgery was based on the prism-determined angle and were lowest in the nonresponders, who had no fusion response to the prisms.

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Twenty-four patients who underwent surgery to correct consecutive exotropia that developed iatrogenically after surgical overcorrection were studied retrospectively. All patients underwent single or bilateral advancement of the medial rectus muscle to the original muscle insertion. The mean preoperative exodeviation was 26.7 prism diopters at distance and 3S.2 Δ at near. Postoperatively, in cases receiving advancement of a single medial rectus, the mean amount of correction was 23.2 Δ at distance and 29.6 Δ at near. In cases receiving bilateral medial rectus advancement, the mean amount of postoperative correction was 26.3 Δ at distance and 39.8 Δ at near. Adduction deficiency was normalized in five patients (71%), while convergence insufficiency was improved in only nine patients (45%) after surgery. Twelve (50%) patients had binocular single vision at distance on a normal or abnormal basis as determined by the Bagolini lens test.

Vertical deviation of the affected eye caused by horizontal change of gaze was measured with a synoptometer in 5 cases of Duane’s retraction syndrome type III. Step-by-step measurement clearly showed two types of incomitance patterns, i.e. upshoot and up- and downshoot in adduction. The former suggests a paradoxical synergistic innervation between the medial rectus and superior rectus muscles, and the latter suggests an abnormal vertical movement of the lateral rectus muscle over the globe on elevation or depression of the eye. Recession of the lateral rectus muscle, however, reduced the vertical deviation regardless of the incomitance pattern.

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