An Objective Photographic Analysis of Ocular Oblique Muscle Dysfunction

Abstract

To develop a new objective method for measuring ocular oblique muscle dysfunction. Prospective, observational study. Twelve healthy volunteers and 27 patients with oblique muscle overaction or underaction in at least 1 eye were included. The corneal contour in 9-gaze photographs was transcribed into an ellipse. A newly developed simulating program depicted the corneal contour as the eyes moved, and graded oblique muscle dysfunction by analyzing the angular difference between the 2 eyes. An angular difference of 5 degrees was defined as 1 unit of overaction or underaction. To verify the accuracy of the method, a masked observer compared the photographic analysis with goniometric readings in the model eye and magnetic search coil recordings in healthy volunteers. The diagnostic accuracy of the photographic analysis was compared with the clinical gradings of patients with oblique muscle overaction or underaction. There was no statistical difference between photographic analysis and goniometric readings of the model eye. Bland-Altman plots showed that there was no overall tendency for the photographic analysis to differ from the scleral search coil values, and the difference fell mostly within ±7 degrees. There was a good correlation between the photographic analysis and the clinical grading of oblique muscle dysfunction (R(2)= 0.618; P< .001). The sensitivity and specificity for detecting oblique muscle overaction were 90.2% and 88.1%, respectively, whereas those for detecting underaction were 81.5% and 80.2%, respectively. A newly developed photographic analysis could provide an objective and accurate means of evaluating ocular oblique muscle dysfunction.