Association Between Compensatory Overaction of the Non-Injured Eye, Measured by HESS Chart and Postoperative Diplopia in Blow-Out Fracture.

In orbital floor fracture, diplopia often persists post-operatively. This study evaluated the association between pre-operative parameters concerning the extent of the injury and post-operative diplopia, using multivariate analysis. A retrospective computed tomography analysis and chart review was performed for patients with punched out orbital floor fracture, who underwent operations during the period from April 2011 to March 2018. Five parameters were evaluated: the number of upward arrows on the Hess chart (representing compensatory overaction of the non-injured eye), time interval to surgery, muscular subscores, fracture area, and swelling rate of the inferior rectus muscle. Of the 32 patients, 9 (28%) had post-operative diplopia; pre-operative diplopia was completely restored in 23 (72%) patients by 6 months after surgery. Univariate analysis found statistically significant differences in the number of upward arrows on the Hess chart, time interval to surgery, muscular subscores, and fracture area. Logistic regression analysis demonstrated that only the number of upward arrows displayed a significantly increased risk for post-operative diplopia (odds ratio, 15.3; 95% confidence interval, 2.0-117.0; P = 0.008). Excessive overaction of the non-injured eye predicted persistent diplopia by 6 months post-operatively. Surgical intervention may be insufficient to achieve full recovery from diplopia and disturbances of ocular motility in some patients.