Thyroid disease and vertical rectus muscle overaction after retrobulbar anesthesia

Abstract

Purpose To determine the associated factors of persistent diplopia after retrobulbar anesthesia. Setting Strabismus Section, Department of Ophthalmology, Seoul Municipal Boramae Hospital, Seoul, Korea. Methods A prism and cover test in the diagnostic positions of gaze, force-generation test, and forced-duction test were performed in 11 patients with vertical rectus overaction after retrobulbar anesthesia. A Tensilon® (edrophonium chloride) test, thyroid function test, and orbit computed tomography were performed in 8 patients. Results None of the 11 patients reported diplopia before receiving local anesthesia. Ten patients showed ipsilateral hypertropia with superior rectus overaction and 1 patient, ipsilateral hypotropia with inferior rectus overaction. One patient had partial fibrosis of the medial half of the superior rectus, presumably caused by a bridle suture. Four (50%) of 8 patients in whom a thyroid function test was performed had abnormal findings; 1 had a history of systemic dysthyroidism. Conclusions In this study, permanent vertical strabismus after local anesthesia was entirely the result of overactive vertical rectus muscles, mostly the superior rectus muscle. Half the patients who had a thyroid function study had abnormal findings.