Postoperative diplopia test-repeatability and prediction of surgical outcomes

The postoperative diplopia test (PODT) is used to assess the risk of postoperative diplopia in older children and adults prior to strabismus surgery for nonfunctional reasons. The purpose of this study was to evaluate the test-retest and interobserver reliability of the PODT and its predictive value in assessing diplopia risk.

In the first phase of this study, the repeatability of the PODT method was prospectively assessed with two groups of patients (group 1, test-retest; group 2, interobserver). In the second phase, notes were reviewed retrospectively to evaluate the predictive value of the PODT.

For phase 1, 39 participants were recruited. In group 1, 12 participants showed agreement in the area of suppression for both near and distance fixation; 8 showed variability. In group 2, 10 showed agreement for near, and 9 showed variability; 9 showed agreement for distance, and 10 showed variability. Group 1 differences ranged from 0 to 9 points (median, 0.5; IQR, 0-3); group 2, from 0 to 36 points (median, 1; IQR, 0-4.5). In phase 2, outcomes of 39 strabismus surgeries were reviewed: none of the patients without diplopia on PODT and 2 of 14 patients with diplopia on PODT had persistent diplopia 3 months after surgery.

Many patients develop diplopia postoperatively, but this generally resolves spontaneously. Current testing procedures have excessive test-retest and interobserver variability and insufficient predictive value to be useful in predicting postoperative diplopia.