Prism adaptation response and surgical outcomes of acquired nonaccommodative comitant esotropia.

Purpose: To investigate the clinical factors influencing the prism adaptation response of acquired non-accommodative comitant esotropia (ANAET) and evaluate the surgical outcomes.

Study design: Retrospective observational study.

Methods: This study assessed patients with ANAET who underwent strabismus surgery based on the results of a short prism adaptation test (PAT). Patients wore Fresnel trial prisms based on alternate prism cover tests in outpatient clinics. The cover test was then performed after 15-20 minutes; if the deviation increased, the power of the prism was increased to neutralize the angle. The test was repeated until the angle was stable. Patients were classified as either prism builders (angle increased by ≥ 10 prism diopters [PD] compared with the entry angle) or prism non-builders (angle increased by < 10 PD). The following clinical characteristics were noted: age at onset, age at surgery, duration of esotropia, refractive error, angle of deviation, presence or absence of intermittent esotropia at near, and pre- and postoperative sensory status.

Results: A total of 41 patients (median age, 15.4 years) were evaluated. The mean (standard deviation) spherical equivalent refractions were -3.03 (3.33) diopters (D) and -3.05 (3.23) D in the right and left eyes, respectively. Twenty-seven (66%) patients were prism builders. The prism builders had greater myopia (builders vs. non- builders, right eye: -3.97 [2.97] vs. -1.22 [3.33] D, P = .01; left eye: -4.08 [2.78] vs. -1.07 [3.20] D; P = .003), lower angle of deviation at near (median [interquartile range] 30.0 [20.0, 35.0] vs. 42.5 [35.0, 49.4] PD; P = .009), much more preoperative intermittent esotropia or esophoria at near (44% vs. 7%, P = .03) and diplopia (96% vs. 64%, P = .01), and better postoperative stereoacuity (50 [40, 110] vs. 100 [60, 400] arcsec, P = .02) than the prism non-builders. The overall success rate was 83%, without a significant difference between the two groups (builders vs. non-builders, 89% vs. 71%, P = .21).

Conclusion: In cases of myopic refractive error, a small entry angle with intermittency at near, and good binocularity, it is recommended that surgery is performed based on prism-adapted angle to prevent under-correction.