Chemodenervation of extraocular muscles with botulinum toxin in thyroid eye disease

Background: Thyroid eye disease (TED) presents a management dilemma for strabismologists due to the variability of its clinical course. Prisms may be prescribed to relieve diplopia in small deviations. Surgical intervention, on the other hand, should not be done until the active phase of the disease has subsided. We report our experience with chemodenervation utilizing botulinum toxin (BT) injection in the management of TED-related strabismus. Methods: A retrospective chart review was done on twenty-two (22) consecutive patients receiving BT injections at the University of California, San Diego (UCSD) Thyroid Eye Center. All BT injections were administered by a single physician under electromyographic guidance. Results: The clinical records of 22 patients (18 females) were reviewed. Seven patients (32 %) had a reduction of their deviation to a point where surgery was not required. In six patients (27 %), surgery was required but an improvement in ocular deviation was found, altering the original surgical plan. In four patients (18 %), the deviation continued to progress after BT injection. Success rates were higher if pre-treatment deviation was less than 20 prism diopters (^∆). Conclusion: One third of the chemodenervation-treated patients avoided surgical intervention, with an additional 27 % (total of 40 % of those who needed surgery) having a reduced deviation prior to surgery. Using BT injection to extraocular muscles to treat diplopia in TED patients is most effective in preventing surgery in those patients with 20^∆ or less of deviation.