Changes of saccadic eye movements in thyroid‐associated ophthalmopathy

Abstract

ABSTRACT.Purpose: To establish whether or not the dynamics of saccadic eye movements are significantly changed in patients with different stages of thyroid-associated ophthalmopathy (TAO) and, subsequently, if analysis of saccades could serve as an additional diagnostic tool for early detection of inflammatory activity in TAO. Methods: Thirty-seven patients with TAO and 10 age-and gender-matched control subjects were investigated. The patients were divided into four groups according to the stage of the disease: (i) early mild disease (n = 10), (ii) early severe disease (n = 11), (iii) long-standing restrictive disease (n = 10) and (iv) proven auto-immune hyperthyroidism without any signs of TAO (n = 6). Horizontal and vertical saccades with amplitudes of 10°, 20°, 30°and 40°were recorded binocularly using the induction scleral search coil technique. The two main sequence constants V max and C were calculated for each eye. Repeated measurement analysis of variance was carried out to test for differences between different gaze directions, eyes and groups. Results: In horizontal saccades, significant differences were found between groups but not between abduction and adduction. In vertical saccades, differences between groups and the interaction between groups and up-and down-gaze saccades were significant. Compared with the control group, analysis of the main sequence curves revealed larger differences in patients of group 3 and 4 than in those of group 1 and 2. Whereas in the control group down-gaze saccades were faster than up-gaze saccades, the opposite behaviour was found in all patient groups. The largest differences were detected among those patients who had no signs of TAO (group 4). Conclusions: In this study, significant saccade differences were detected in all patients with TAO. In contrast to our earlier studies where evaluation of multiple individual saccade parameters did not reveal significant differences, analysis of the main sequence constants and mathematical reconstruction of the main sequence curves turned out to be a sensitive technique for reliable detection of subtle ocular motility changes. Significant differences were detected even in patients with auto-immune thyroiditis where no clinical signs of TAO were apparent.

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

“…Our previous study analyzed the saccades of patients with hyperthyroidism without obvious eye symptoms and revealed a significant difference in saccade dynamics, including V max , increased peak acceleration and short latencies, during VGS between affected patients and healthy controls (18). These previous results were similar to those published in other previous studies (16).…”

“…As TAO progresses, chronic fibrosis in eye tissues can decrease eye coordination (42). Previous studies have revealed that the saccades of patients with a long TAO course were abnormal (16); however, to the best of our knowledge, no study has investigated TAO with the disease course of hyperthyroidism. In future studies, the authors of the present study will continue to analyze the relationship between the course of hyperthyroidism and the initiation of TAO pathogenesis.…”

“…Once fibrosis occurs, the organization of the eyeball cannot be restored to its former healthy status, and the patient still experiences residual symptoms and chronic external eye muscle dysfunction (4). During this period, the damage to saccades in patients is obvious, which is the consensus reached by the majority of TAO studies related to saccades (15,16). It is difficult to treat TAO once fibroplasia occurs (32).…”

“…A grade >3, which is based on the patient's exophthalmia (19). Lower NOSPECS grading (0-2) status is based primarily on eyeball symptoms and signs, which can be easily missed by doctors (16). At present, the lack of sensitive objective examinations for patients with early TAO remains problematic (33).…”

“…Previous studies have investigated TAO and saccadic function, and the results have suggested that saccadic functions are abnormal in hyperthyroidism (16,17). Our previous studies evaluated basic visually guided saccade (VGS) to explore the potential for eye damage in first-episode treatment-naive hyperthyreosis patients without pre-existing eye symptoms.…”