Initial versus subsequent postoperative motor alignment in intermittent exotropia

Although initial overcorrection is believed to be important after bilateral lateral rectus muscle recessions for intermittent exotropia, not all patients with desirable amounts of initial overcorrection have good final outcomes. The purpose of this study is to evaluate the relationship between initial postoperative and subsequent postoperative motor outcomes in a group of patients operated on for intermittent exotropia.

All patients on whom I performed bilateral lateral rectus muscle recessions as the initial surgical procedure for intermittent exotropia and who had at least 6 months of postoperative follow-up were included in this study.

Of the 60 patients in this study, 38 (63%) had good outcomes (< or = 10 PD exophoria or < or = 5 PD esophoria), 15 (25%) had undercorrection (> 10 PD exodeviation), and seven (12%) had overcorrection (> 5 PD esodeviation). The chance of a good outcome was highest with initial postoperative alignment between orthotropia and 9 PD of esotropia, but 22% of patients with alignment in this range after the operation ended up overcorrected or undercorrected. Most patients had an exotropic drift after the operation, but seven patients had a drift in an esotropic direction.

Although an initial alignment within the range of orthotropia to 9 PD of esotropia during the first few days after the operation is desirable for patients with intermittent exotropia, alignment within this range does not guarantee a good final outcome, nor does alignment outside this range guarantee a bad outcome. Little predictability exists with respect to the amount and occasionally even the direction of postoperative drift. This unpredictability may in part reflect the artifactual nature of the initial postoperative measurement.