High myopia extends beyond a refractive error: evidence from fixation stability and reading-related saccadic eye movements

This study aimed to evaluate fixation stability and reading-related saccadic eye movements in high myopes compared to emmetropic controls. In this cross-sectional study, 29 emmetropic and 23 high myopic participants were included. Participants underwent comprehensive ophthalmic examination, axial length measurement, and infrared eye-tracking software (Clinical Eye Tracker, Hatfield, UK). Fixation stability was assessed via bivariate contour ellipse area (BCEA) derived from raw gaze data during a 10-second binocular fixation task. Saccadic parameters during reading (reading speed, regression count, fixation count, and duration) were analyzed. Statistical comparisons used independent t-tests and Mann-Whitney U tests. High myopes showed significantly higher BCEA values (BCEA 68%: 2.338 ± 0.020 vs. 0.865 ± 0.017 deg², p < 0.001), indicating reduced fixation stability. Reading speed was similar (259.34 ± 17.21 vs. 249.11 ± 24.49 words/min, p = 0.095), but regressions (18.26 ± 5.84 vs. 10.10 ± 2.17, p < 0.001), total number of fixations (99.12 ± 9.87 vs. 63.26 ± 4.24, p < 0.001) increased, and mean fixation duration decreased (160.43 ± 36.11 vs. 349.12 ± 34.73 ms, p < 0.001). High myopia is associated with fixation instability and compensatory saccadic changes during reading. These findings highlight myopia’s oculomotor impacts beyond refraction and suggest eye-tracking metrics as biomarkers for functional impairment.