Clinical characteristics of intermittent exotropia in 5,385 Koreans by age at presentation: a nationwide multicenter, cross-sectional study

We investigated the clinical characteristics of intermittent exotropia (IXT) according to age at presentation. A total of 5,385 patients with IXT of ≥ 8 prism diopters (PD) at distance (D) or near (N) fixation were included between March 2019 and February 2020. Participants were grouped by age at presentation: Group 1 (G1: 0 ≤ age < 3 years), Group 2 (G2: 3 ≤ age < 10 years), Group 3 (G3: 10 ≤ age < 19 years), and Group 4 (G4: age \(\:≥\:\) 19 years). Clinical manifestations and subjective symptoms were compared among age groups. The proportion of female patients was higher in the younger groups (G1 and G2). Duration of disease was significantly short in G1 (0.72 ± 0.75 years) and long in G4 (9.37 ± 11.67 years). Mean angles of deviation were the largest in the oldest group (30.95 ± 17.02 PD at D and 33.52 ± 17.01 PD at N). Basic type was the most common in all age groups, with divergence excess type more frequent in G1 (8.1%) and convergence insufficiency type more common in G3 (19.8%) and G4 (14.8%). Cycloplegic refraction was in hyperopic side in G1, whereas in myopic side in G3 and G4. Oblique dysfunction was least frequent in G1 (17.4%) and most frequent in G4 (34.5%). Stereopsis results, family history of strabismus, and history of perinatal complications did not differ across the age groups. Abnormal head posture and subjective symptom complaints tended to be more prevalent in older age groups. This is one of the largest clinical studies on IXT identifying various age-related characteristics in IXT.