Effect of the amount of inferior rectus muscle recession on lower eyelid position in thyroid eye disease

Objective. The study evaluated the relationship between the amount of inferior rectus muscle (IRM) recession and subsequent lower eyelid (LE) retraction in patients with thyroid eye disease (TED). Material and methods. The study included 40 patients (40 eyes) with inactive TED and IRM involvement confirmed by multislice computed tomography of the orbits. All patients underwent IRM recession of 4.5 to 9 mm. Before and after surgery (on days 1 and 7, at 2—3 months, and at 6 months), LE position was photoregistered with the head and gaze in the primary straight position. The distances from the center of the pupil to the lower eyelid margin (MRD2) and from the lower limbus to the eyelid margin (MLD2) were measured using Adobe Photoshop software, with pixels converted into millimeters. The data were analyzed using SPSS software (Statistical Package for the Social Sciences, version 2.0). Results. According to the obtained data, lower eyelid position changed on day 1 in 100% of cases, and MRD2 and MLD2 values increased compared with preoperative values. LE retraction significantly increased over time in the postoperative period, reaching maximum values by the third month, further changes were minimal. Analysis of data on day 1 after surgery showed no significant correlation between the amount of IRM recession and the degree of LE retraction. However, analysis at 3—6 months revealed a weak positive correlation: the greater the amount of IRM recession, the higher the degree of LE retraction by this time point. Conclusion. The degree of LE retraction increases during the postoperative period and reaches maximum values by 3—6 months. After LE position stabilizes at 3 months or later, a weak positive correlation is observed between the amount of IRM recession and the degree of LE retraction. However, its severity appears to depend not only on the amount of recession but also on a complex of individual anatomical features and the degree of tissue involvement in the pathological process.