Session: Poster session B

Clinical Characteristics of Intermittent Exotropia in 5,385 Koreans by Age at Presentation: The Korean Intermittent Exotropia Multicenter Study

Seung-Hee BAEK¹, Won Yeol RYU², Hae Jung PAIK³

¹Department of Ophthalmology, Kim's Eye Hospital , Seoul, Korea (Republic of)
²Department of Ophthalmology, Dong-A University College of Medicine, Busan, Korea (Republic of)
³Department of Ophthalmology, Gachon University Gil Medical Center, Incheon, Korea (Republic of)

Introduction: The Korean Intermittent Exotropia Multicenter Study (KIEMS) is a nationwide cross-sectional multicenter study of intermittent exotropia (IXT) involving 65 ophthalmologists from 53 institutions in South Korea. We investigated the clinical characteristics of IXT patients in KIEMS by age.

Methods: Total 5385 patients with IXT ≥ 8 PD at distance or near fixation were included between Mar 2019 and Feb 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). Gender, deviation angles, IXT type, oblique muscle function, binocular sensory outcome and cycloplegic refraction were compared among age groups.

Results: Proportions of females were higher in younger groups (G1: 62.6%, G2: 52.8%), while lower in older groups (G3: 41.5%, G4: 45.9%). Disease duration was significantly different among groups (p<0.001 by ANOVA), with the shortest in G1 (0.72 ± 0.75 year) and the longest in G4 (9.37 ± 11.67 years). Deviation angles decreased after age 1, started to increase during school age, and was largest in G4.

Basic type was the most common type 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%). While good stereopsis was less common in G1 (23.2%) and G4 (35.6%) than in G3 (47.9%) and G4 (51.1%), differences among age groups were not significant (p=0.416 by Chi-square test).

Conclusions: In this Korean IXT study, the oldest age group demonstrated the longest IXT duration and the largest deviation angles, and on the contrary to younger groups under 10 years of age, exhibited myopic refraction, a higher proportion of males, convergence insufficiency type, and oblique dysfunction.