Comparison of Clinical Features between Two Different Types of Exotropia before 12 Months of Age Based on Stereopsis Outcome

Purpose: To compare the clinical outcomes and characteristics of 2 different types of early-onset exotropia on the basis of stereopsis outcome. Design: Retrospective case series. Participants: A total of 24 patients with newly diagnosed exotropia before 12 months of age and at least 1 year of follow-up after surgery. Methods: The clinical records of all patients were reviewed. Patients were divided into 2 groups according to stereopsis. The presumable early-onset intermittent exotropia (EIE) group was composed of 6 patients (25%) who showed excellent stereopsis of >= 60 arc seconds. The primary infantile exotropia (PIE) group was composed of 18 patients (75%) who showed stereopsis of <= 100 arc seconds. We compared the preoperative and postoperative clinical features of the 2 groups. Main Outcome Measures: The age at onset and visit, age at surgery, constancy before surgery, preoperative and postoperative angles of deviation, distant suppression, reoperation rate, and presence of dissociative vertical deviation (DVD) and inferior oblique overaction (IOOA). Results: The age at the stereopsis test was 6.8 years in the EIE group and 6.4 years in the PIE group (P = 0.41). There was no statistical difference in the mean preoperative exodeviation (32.8 prism diopters [PD] in the EIE group vs. 34.7 PD in the PIE group, P = 0.58) and postoperative deviation at the stereopsis test (1.0 PD in the EIE group vs. 2.0 PD in the PIE group, P = 0.97). The reoperation rate was 33% in the EIE group and 27% in the PIE group (P = 1.00). There was no statistical difference in constancy between the EIE and PIE groups (33% vs. 56%, respectively, P = 0.64). However, DVD (61%) and IOOA (56%) were noted only in the PIE group (P = 0.016, P = 0.024, respectively), and distant suppression was noted only in the PIE group (61%, P = 0.016). Conclusions: The results indicate that excellent sensory outcome was observed in only 25% of patients with exotropia before 12 months of age, but motor outcome and reoperation rate were not different between the 2 types of exotropia. We observed DVD, IOOA, and distant suppression only in the PIE group.