Short prism adaptation test in patients with acquired nonaccommodative esotropia; clinical findings and surgical outcome.

PURPOSE: To evaluate the surgical outcomes in patients with acquired nonaccommodative esotropia operated on based on a short prism adaptation test (PAT) and to determine the subgroup of patients most responsive to PAT.

METHODS: In this prospective interventional cases series, patients with acquired nonaccommodative esotropia were enrolled. Patients wore Fresnel trial lenses based on the results of alternate prism-cover testing. With the Fresnel prism in place, alignment was measured after 20 minutes. If deviation increased, the power of prism was increased to neutralize this angle. The test was repeated every 20 minutes to achieve motor stability. Patients were classified as either prism responders (if the angle of deviation increased >10Δ compared to the entry angle) or prism nonresponders. All patients underwent bilateral medial rectus muscle recession. Prism responders underwent surgical correction based on the enhanced angle.

RESULTS: Of the 28 subjects enrolled, 14 (50%) were prism responders and 14 (50%) were classified as prism nonresponders. After 6 months, 100% of prism responders and 92.9% of nonresponders were aligned within 8Δ of orthotropia at distance and near fixation. None of the patients with an entry angle of >30Δ were prism responders.

CONCLUSIONS: In our study cohort, a short PAT with an endpoint of motor stability in patients with acquired nonaccommodative esotropia was associated with a good surgical outcome and a low rate of over- and undercorrection. PAT may be unnecessary for patients with an angle of deviation of >30Δ .