Purpose: To measure the magnitude of the effect of attention on upper eyelid retraction in patients with thyroid orbitopathy (Kocher sign) and to determine if Müllerectomy can abolish this effect. Methods: The study design was prospective with two phases: The first one was observational and the second interventional. Two groups of eyes were studied. The control group consisted of 30 eyes of 30 healthy subjects. The second group included 34 eyes of 17 patients with thyroid orbitopathy and hyperthyroidism. The mid-pupil to eyelid margin distance of both groups was measured when the subjects were relaxed and during attentive gaze. The same measurements were performed for the patients with thyroid orbitopathy after Müllerectomy. All measurements were performed on digitalized images of the palpebral fissure with software on a Macintosh computer. Results: Attention induced a mean increment of 1.33 mm in the mid-pupil eyelid margin distance of patients with thyroid orbitopathy. For the control subjects, attention did not modify the position of the upper eyelid. After Müllerectomy, the effect of attention was abolished. Conclusions: Müllerectomy abolishes the variability of upper eyelid retraction induced by attentive gaze in patients with thyroid orbitopathy.
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