Postoperative stereoacuity following realignment for chronic acquired strabismus in adults

Background: There is controversy regarding whether or not visually mature individuals can permanently lose stereoacuity and under what conditions stereoacuity can be regained. Some have proposed a critical duration of misalignment in adults beyond which recovery of fine stereoacuity is not possible, despite successful surgical alignment. Methods: Twenty-one adult patients (median age 59 years) with large-angle acquired strabismus and who were successfully surgically aligned after 7 to 501 months of misalignment were studied. Subjects had no evidence of motor or sensory fusion since the onset of strabismus, on preoperative exam, or by history. Stereoacuity was measured using 1 or more of the Frisby, Preschool Randot and Titmus tests, at 8 weeks and at 12 months. Data from tests with monocular clues were not used. Results: At total of 67% of patients with chronic acquired strabismus and no preoperative fusion regained measurable stereoacuity and 44% regained fine stereoacuity of at least 60 seconds of arc. Of 10 patients with no or subnormal stereoacuity 8 weeks postoperatively, 6 (60%) showed improvement at the 12-month visit. Misalignment for up to 4 years did not preclude the development of postoperative stereoacuity. Conclusions: Although a minority of adult strabismus patients may permanently lose stereoacuity despite successful alignment for acquired strabismus, the majority do show recovery. Such recovery of stereoacuity may take several months to occur. In our adult series, duration of misalignment did not predict failure to recover stereoacuity.