Relationships between fusional convergence, suppression depth, and exotropia control in intermittent exotropia.

Purpose: To assess the correlation between the contribution rates of fusional convergence from the dominant and non-dominant eye and suppression depth and exotropia control. Study design: Cross-sectional prospective study. Methods: The fusional convergence of 25 participants with intermittent exotropia (mean age 10.8 ± 3.4; range 6-18 years) was measured with an eye-tracking system. The contribution rate was defined based on the amplitude of fusional convergence during refusion relative to the exo-deviation angle. The suppression depth was assessed, and exotropia control was evaluated using the intermittent exotropia Office Control Score. We analyzed the correlations between the contribution rate from the dominant and non-dominant eyes and the suppression depth or control score. Results: There was a negative correlation between the dominant eye's contribution rate and the suppression depth in both eyes (r = -0.85, 95% confidence interval [CI]: -0.97 to - 0.20 in the fixated dominant eye and r = -0.91, 95%CI: -0.95 to - 0.40 in the fixated non-dominant eye). There was a negative correlation between the dominant eye's contribution rate and the control score at a 4-meter distance (r = -0.53, 95%CI: -0.76 to - 0.17). Conclusion: Suppression in intermittent exotropia patients could affect the fusional convergence in the dominant eye.

Changes in saccadic eye movement and smooth pursuit gain in patients with acquired comitant esotropia after strabismus surgery.

This study investigates the change in horizontal saccadic eye movement and smooth pursuit in patients with acquired comitant esotropia (ACE), before and after strabismus surgery. The horizontal saccades and pursuit in 11 patients with ACE were recorded using a video eye-tracker under binocular viewing before and after strabismus surgery. Participants were instructed to fixate on the new target as rapidly as possible when it randomly appeared at either 18.3° rightward or 18.3° leftward. For smooth pursuit, participants were asked to track, as accurately as possible, a step-ramp target moving at ±6.1°/s. The asymmetry of adduction-abduction and the binocular coordination in gains of saccade and pursuit were compared between the pre- and post-surgical data. The asymmetry of adduction-abduction saccade gain in each eye after surgery tended to be smaller than that before surgery. The binocular coordination of saccade showed significant improvement after surgery in only the non-dominant eye direction. Adduction-abduction asymmetry in the smooth pursuit gain in each eye after surgery tended to be smaller than before surgery. After surgery, the binocular coordination of pursuit was improved significantly in both directions. In patients with ACE, binocular coordination of saccade and smooth pursuit was poor. Binocular coordination of saccade and pursuit seems to be improved due to the improvement in ocular deviation angle and binocular visual function after surgery.