Clinical Study for the Undercorrection Factor in Intermittent Exotropia

PURPOSE The surgical technique for intermittent exotropia [X(T)] is quite simple. However, in many cases, the condition recurs due to any one of a number of causes, including undercorrection. This study examined the factors associated with undercorrection on X(T) patients. METHODS The study examined 199 X(T) patients who underwent bilateral recession of the lateral rectus muscle or unilateral recession of the lateral rectus muscle and resection of the medial rectus muscle, and who were followed-up for more than a year. Patients whose near and far distance angles of deviation were 9 prism diopters (PD) or more at one year after surgery were designated as group 1. Those whose PD was 8 or below or who had orthophoria were assigned to group 2. Various factors were compared and analyzed. RESULTS One day after surgery, group 1 showed an average overcorrection of 1.9 and 4.1 PD at near and far, respectively, and group 2 showed an average overcorrection of 6.3 and 7.6 PD at near and far, respectively. A statistically significant difference was observed between the two groups (p < 0.05). Factors such as the age of onset of strabismus, age at the time of surgery, the interval from the onset of strabismus to surgery, the preoperative angle of deviation, the dissociated vertical deviation, amblyopia, anisometropia and vertical strabismus had no influence on the undercorrection of X(T) patients (p > 0.05). CONCLUSIONS Of the many factors that might influence the surgical results of X(T) patients, the angle of deviation during the initial postoperative period is the most important factor.