Clinical Validity of the 15-Degree Hess Area Ratio as a Postoperative Functional Outcome Measure in Orbital Blowout Fracture

Orbital blowout fractures (BOFs) often result in diplopia and impaired ocular motility due to the entrapment of orbital contents. The Hess screen test is a widely used method for evaluating ocular motility. However, performing a full 30 degrees Hess chart is not always feasible in clinical practice. This retrospective preliminary study aimed to evaluate the clinical validity of the 15-degree Hess Area Ratio (HAR%) as an objective indicator of functional recovery after surgical repair of BOF. Eight patients with pure BOFs who underwent surgical reconstruction and both preoperative and at least 6-month postoperative 15-degree Hess testing were included. Subjective diplopia was evaluated using a standardized 5-point scale, and HAR% was calculated from Hess chart plots using ImageJ software. The mean 15-degree HAR% improved from 64.5% preoperatively to 91.6% postoperatively. The average diplopia score also improved from 2.5 to 0.9. A statistically significant negative correlation was observed between postoperative HAR% and diplopia scores (r=-0.729, P=0.040). Notably, the 15-degree HAR% was measurable in all cases, whereas the 30-degree HAR% could not be assessed in most patients due to limited cooperation. These findings suggest that the 15-degree HAR% may serve as a reliable, practical, and objective measure of postoperative ocular motility in patients with BOFs. Its relatively strong correlation with subjective diplopia further supports its clinical utility as an alternative to the 30 degrees test, particularly in patients with limited tolerance. The 15-degree HAR% may serve as a valuable tool for both clinicians and researchers in evaluating functional outcomes following orbital fracture repair.