Diagnosis and surgical management of strabismus associated with thyroid-related orbitopathy

In the healing phase of thyroid-related orbitopathy, fibrosis and contracture of the extraocular muscles may result in restrictive ocular motility. Ocular misalignment may occur in both eyes and along three different axes of rotation. Successful surgical treatment depends on precise identification of the muscles that are restricting motility and producing the misalignment.

Between 1980 and 1994, 22 patients were surgically treated for restrictive strabismus caused by thyroid-related orbitopathy. Preoperatively, all patients underwent complete neuroophthalmic, oculoplastic, and orthoptic examinations. Analysis of ductions, measurement of torsion, and the use of monocular neutralization techniques were essential additions to the usual motility exam. Patients were placed into diagnostic categories based on the clinical pattern of extraocular muscle restriction. Adjustable recessions were done for all initial surgeries.

Patients with unilateral inferior rectus involvement or with ipsilateral inferior rectus-contralateral superior rectus involvement had large vertical deviations (equal to or > 20 prism diopters [delta]). Patients with bilateral inferior rectus involvement had small vertical deviations (< 20 delta). Excyclotorsion correlated strongly with the presence of tight inferior recti. Vertical comitance (upgaze versus downgaze measurement of equal to or < 15 delta) correlated with the ipsilateral inferior rectus-contralateral superior rectus pattern of involvement. Vertical incomitance (upgaze versus downgaze measurement of > 15 delta) correlated with unilateral inferior rectus involvement. Eighteen of 22 patients had excellent postoperative alignment and elimination of diplopia in functional positions of gaze. Those with less favorable results developed reversal of the hypertropia and exotropia in downgaze. Sixteen out of 19 patients who underwent inferior rectus recession had induced inferior eyelid retraction.

Different combinations of extraocular muscle restriction in this series of patients produced characteristic patterns of misalignment. Appropriate, adjustable, strabismus surgery was successful in restoring binocular vision in 21 out of 22 patients with a minimum of complications.