A Comparative Study of Prism Adaptation and the Augmented Surgery Formula in the Management of Acquired Comitant Esotropia

Purpose: To compare two methods of surgical augmentation (prism adaptation and the augmented surgery formula) in the management of acquired comitant esotropia. Methods: Forty patients were included in this prospective study and assigned to either the prism adaptation (20 patients) or augmented surgery (20 patients) group. After preoperative prism adaptation, patients in the prism adaptation group were classified as prism adaptation responders (fusers) or non-responders (non-fusers). All patients in the prism adaptation group underwent surgery for the prism-adapted angle. Patients in the augmented surgery group underwent surgery based on the augmented surgery formula, defined as the average of the near deviation without correction and the distance deviation with correction. Results: In the prism adaptation group, 6 patients (30%) were prism responders, whereas 14 (70%) were non-responders. The 3-month motor success rate was significantly higher in the prism adaptation group (90%) than the augmented surgery group (55%) (P = .013). The 6-month motor success rate was not significantly higher in the prism adaptation group (95%) than the augmented surgery group (80%) (P = .151). The improvement in the 6-month outcome was mainly attributed to hyperopic spectacle power reduction after 3-month postoperative evaluation to correct consecutive exotropia. Conclusions: Although prism adaptation is superior in precisely determining the surgical target angle, the success rates were comparable between the two groups after hyperopic spectacle power reduction. This obviates the need for prism adaptation, except in cases of non-accommodative esotropia.To maximize the benefit of prism adaptation, it is recommended that all patients with prism adaptation (responders and non-responders) undergo surgery for the prism-adapted angle.