Objective Analysis of Reading Ability Using an Eye Tracker in Intermittent Exotropia

Background/Objectives: This study's objective was to analyze the reading ability in patients with intermittent exotropia using an eye tracker and determine how the clinical characteristics of intermittent exotropia may affect reading ability. Methods: We compared the reading speed (LPS; letters per second) of 25 intermittent exotropia patients to 25 age-matched normal controls who were 13 years old or older with best-corrected visual acuities of ≥20/25. Correlations between reading ability and clinical characteristics of intermittent exotropia were evaluated. Results: Reading speed was significantly slower in the intermittent exotropia group (6.1 ± 0.81 LPS) than in the control group (6.8 ± 1.11 LPS, p = 0.014). The Newcastle control scores, Mayo Clinic office-based scale and the patients' deviation angle were not significantly related to reading speed (p = 0.132, 0.197, and 0.807, respectively). Fixation disparity score measured with an eye tracker during the reading task showed a statistically significant negative correlation with reading speed (Spearman's rank correlation coefficient = -0.458, p = 0.028). Conclusions: Reading speed was slower in patients with intermittent exotropia compared to age-matched controls without strabismus. Only objective fusional control scores measured with an eye tracker showed significant correlation with the reading speed.