Objective: To investigate the dose-effect relationship of strabismus surgery in patients with thyroid associated ophthalmopathy (TAO).
Methods: Thirty cases (32 eyes) with TAO treated with extraocular muscle surgery by the author seen between Jan 1999 and March 2006 in Zhongshan Ophthalmic Center, Sun Yat-sen University, China were reviewed retrospectively.
Results: Out of the 30 cases (32 eyes), 19 cases were male and 11 were female, with their age ranging from 22 to 68 (mean 49.4 years). The right eye was involved in 11 cases and the left one in 21 cases. The extraocular muscle surgery included recession of inferior rectus muscle (10 muscles), recession of superior rectus muscle (10 muscles), recession of medial rectus muscle (6 muscles), recession of inferior rectus muscle combined with medial rectus muscle (2 eyes), recession of superior rectus muscle combined with medial rectus muscle (1 eye), tenotomy of superior rectus muscle (3 muscles). Thirty cases obtained excellent results, and the rate of ocular alignment was 93.75%. By calculating the dose-effect on 28 successfully corrected (<or= +/- 5 degrees) cases who were undergone recession, we found out that the deviation of (3.93 +/- 1.67) degrees on average can be corrected by one millimeter recession of rectus muscle surgery. The corrected amount in superior rectus muscle was minimum, which was (2.63 +/- 0.83) degrees /mm, and the maximum was in medial rectus muscle, which was (5.33 +/- 1.46) degrees /mm; the corrected amount in inferior rectus muscle was (4.11 +/- 1.55) degrees /mm. If the preoperative deviation was equal to or less than 15 degrees, the corrected amount on average was (2.30 +/- 1.09) degrees /mm; if the preoperative deviation was in the range of 16 degrees to 30 degrees , the corrected amount on average was (3.56 +/- 0.79) degrees /mm, and if the preoperative deviation was more than 30 degrees, the corrected amount on average was (6.02 +/- 1.01) degrees /mm.
Conclusion: The patients with strabismus in TAO whose corrected amount of deviation by one millimeter recession of rectus muscle on average was greater than that of patients with other kinds of strabismus. The larger the deviation, the more the corrected amount of one millimeter recession of rectus muscle. It was difficult to estimate the surgical effect on patients with strabismus in TAO before surgery.