The prism adaptation test in the preoperative evaluation of esodeviations

We performed surgery according to the measurements found with the prism adaptation test (PAT) in 14 patients with acquired esodeviations. The amount of deviation, as determined with the prism cover test, ranged from 3 to 30 (mean 13.4) prism dioptres (PD) at distance. Prism-adapted deviations ranged from 31 to 57 (mean 41.2) PD. The average recession of the medial rectus was 4.8 mm, and the average resection of the lateral rectus was 6.7 mm. The mean esodeviation at distance after surgery was 6.8 PD. Our results suggest that the PAT may be useful and perhaps indispensable in the preoperative assessment of patients with certain types of acquired esodeviation.