Hess area ratio and diplopia: evaluation of 30 patients undergoing surgical repair for orbital blow-out fracture

Abstract PURPOSE: To determine if the Hess area ratio is effective in predicting postoperative diplopia in patients undergoing surgery for orbital blow-out fracture. METHODS: Our retrospective, interventional case series study involved 30 consecutive cases affected by orbital fractures and diplopia undergoing surgical correction within 7 days after injury. To evaluate ocular motility disturbance, we measured the involved ocular motility range by use of a manual Hess screen test before and 4 months after surgery. The percentage of Hess area ratio % was used to express the range of ocular motility in a numerical value. RESULTS: All patients with preoperative Hess area ratio >85% had no postoperative diplopia, and most patients (57%) having a preoperative Hess area ratio <65% had postoperative diplopia. When the Hess area ratio was between 65% and 85%, surgical outcomes were variable and most patients (55%) described no problematic diplopia in the peripheral visual field. CONCLUSIONS: The Hess area ratio is a useful procedure to convert Hess graphic representation in a numerical value so that Hess chart data can be compared among clinicians and used to predict surgical outcomes in patients undergoing surgery for orbital blow-out fractures.