Preliminary study of abnormalities in saccade dynamics in patients with hyperthyroidism with no pre-existing eye damage.

The present study investigated the relationship between hyperthyroidism and thyroid-associated ophthalmopathy by examining saccade dynamics to identify defects in eye tracking in patients with hyperthyroidism with no pre-existing eye damage and sensitive indicators that discriminated eye tracking ability in hyperthyroidism. A total of 33 outpatients with hyperthyroidism and 26 healthy controls participated in visually guided saccade (VGS) analysis. Patients with hyperthyroidism were divided into groups based on their medication status (medicated vs. unmedicated). Main sequence analysis was performed to identify differences in peak velocity and duration, and a general linear model (GLM) was used to identify differences in latency, peak acceleration and peak deceleration among the groups. The present study compared differences in the Spearman's correlation coefficient of the duration of saccades and the acceleration asymmetric index (R) among the groups. V values (V was the asymptotic value of the PV of saccades of large amplitude) were significantly different between the healthy control and unmedicated-hyperthyroidism groups. The results of the GLM-based analysis indicated no significant differences in saccade latency among the three groups. Peak acceleration was significantly different between the healthy control and unmedicated-hyperthyroidism groups (P<0.01). Peak deceleration was significantly different between the healthy control, unmedicated- and medicated-hyperthyroidism groups (P<0.01). R was significantly different between the healthy control and medicated-hyperthyroidism groups (P=0.004). The results of the present study suggested that patients with hyperthyroidism with no pre-existing eye damage exhibited significantly altered saccade dynamics during VGS. Therefore, R may be used as an indicator to monitor the level of eye movement coordination.