Evaluation of ocular motility deviation changes in exotropic patients after cycloplegic eye drops versus prism adaptation test

Purpose: To evaluate changes in ocular motility deviation with cycloplegic eye drop examination compared to the prism adaptation test in patients with strabismus. Methods: The medical charts were reviewed of all patients who underwent primary strabismus surgery in our center from December 2013 to July 2015. Data collected included demographics, medical history, and findings on pre-operative ophthalmic/orthoptic examination. Ocular motility deviation was measured before instillation of cycloplegic eye drops, immediately after maximal dilation (end point), and 10 and 20 min later. Prism adaptation test readings were taken at baseline, immediately after prism removal (end point), and 10 and 20 min later. Results: A total of 43 patients had complete pre- and post-operative evaluations. Our analysis focused only on the exotropic patients (n = 33). On cycloplegics, there was no significant difference in ocular motility deviation between baseline and end point for distance and near (p = 0.584, p = 0.468, respectively). On prism adaptation test, comparison of ocular motility deviation between baseline and end point was statistically significant for distance and near (p = 0.002, p = 0.001, respectively). Changes remained significant 10 min after the end point for near (p = 0.011). Comparison at the end points between the tests revealed statistical significance for distance and near, favoring the prism adaptation test (p = 0.001 and p < 0.001, respectively). This significance was maintained even after 10 min for near (p = 0.036). Conclusion: The prism adaptation test is preferred over cycloplegic eye drops for the evaluation of maximal reserve of distance/near motility before surgical correction of exotropia.