Distance Suppression as a Predictive Factor in Progression of Intermittent Exotropia

To address the natural course of intermittent exotropia with small exodeviations (less than 20 prism diopters [PD]) according to the status of suppression, and to evaluate whether suppression testing at the initial visit can assist in predicting the progression of intermittent exotropia.

Clinical records of patients at the Korea University Anam Hospital, Seoul, Korea diagnosed between January 2014 and December 2018 with basic-type intermittent exotropia and initial distance deviations of less than 20 PD, older than four years of age and a minimum of three follow-up visits within a 6-month span were retrospectively reviewed. The participants were divided into two groups, the suppression group and the non-suppression group, based on the Vectogram results at the initial visit. Clinical characteristics, rate of surgery, and rate of progression were compared between the two groups.

A total of 71 patients were included. Among them, 16 patients (22.5%) had visual suppression at the initial visit, while 55 patients (77.5%) had no suppression. At the initial visit, the mean distant angle of deviation was 13.7 ± 3.2 PD (range, 4 to 18 PD) in the suppression group and 12.7 ± 3.4 PD (range, 10 to 18 PD) in the non-suppression group. Ten patients (62.5%) underwent surgery in the suppression group and 12 patients (21.8%) underwent surgery in the non-suppression group (p < 0.01). Eleven patients (68.8%) in the suppression group and 13 (23.6%) in the non-suppression group developed progression (p < 0.01).

Suppression testing was important to predict the progression of intermittent exotropia, in patients with exodeviation angles less than 20 PD at the initial visit.