Change in proptosis following extraocular muscle surgery: effects of muscle recession in thyroid-associated orbitopathy.

PURPOSE: To evaluate the effect of strabismus surgery on proptosis in patients with thyroid-associated orbitopathy. METHODS: The medical records of 22 consecutive patients with thyroid-associated orbitopathy undergoing strabismus surgery were reviewed. Data pertaining to the number of muscles operated on, amount of muscle recession, prior orbital decompression, and exophthalmometry were evaluated. RESULTS: Thirty-eight eyes in 22 patients with thyroid-associated orbitopathy were studied before and after strabismus surgery. The mean change in exophthalmometry following strabismus surgery in all eyes was +0.6 mm (p < 0.01). Eyes with prior decompression averaged a 0.9 mm increase following strabismus surgery (p < 0.01); those without decompression averaged a 0.2 mm decrease (p = 0.658). In eyes that underwent two rectus muscle recessions the increase in Hertel measurements averaged 1.2 mm; when only one muscle was recessed, the average increase was 0.2 mm. In the eyes with muscle recession < or =5 mm, the mean exophthalmometric increase was 0.7 mm. When a muscle recession of more than 5 mm was performed, the exophthalmometry showed a mean increase of 0.5 mm. CONCLUSIONS: Strabismus surgery on patients with thyroid-associated orbitopathy can worsen proptosis, especially in those with prior decompression. When planning for orbital decompression, the surgeon should consider this effect. Moreover, patients should be made aware of the possible changes to their appearance.