Abstract:

Objective

The aim of this study is to analyze the clinical characteristics and surgical outcomes of restrictive strabismus caused by thyroid-associated ophthalmopathy（TAO）.

Methods

A total of 48 TAO patients（68 eyes）who underwent surgical intervention for restrictive strabismus at the Department of Ophthalmology，Renmin Hospital of Wuhan University，between January 2019 and March 2023 were retrospectively collected.The final participants included 33 males（44 eyes）and 15 females（24 eyes）with amean age of（51.7±10.3）years（ranging from 33 to 66）.Affected extraocularmuscles were identified preoperatively via ocularmotility assessments，imaging，and intraoperative forced pull tests.Surgical strategies included extraocularmuscle tenotomy，suspension surgery，retraction surgery，or type A botulinum toxin injection，with additional strengthening surgery for residual deviation.Patientswere followed up for 6 months or 1 year after surgery and analyzed for differences of in ocular deviation，diplopia，intraocular pressure，visual acuity，and proptosis between the preoperative period and the last follow-up.Measurements of age，limitation degree of ocularmotility，strabismus deviation，intraocular pressure，visual acuity，and proptosiswere described as¯x±s when they conformed to normal distribution，and compared by t tests；paired t tests were used for preoperative and postoperative comparisons.Disease duration and the interval between thyroid dysfunction and strabismus were described by quartiles due to they did not conform to normal distribution；count data were described by number of cases and percentage.

Results

The duration of strabismus ranged from 5 to 108 months，with amedian duration of12 months，and the duration of thyroid dysfunction ranged from 7 to 120 months，with amedian duration of20months；themedian interval between thyroid dysfunction and strabismus ranged from 0 to 114 months，with a median interval of 6 months.45 patients（64 eyes）had a previous diagnosis of TAO，2 cases（3 eyes）with papillary thyroid carcinoma，and 1 case（1 eye）with Hashimoto′s thyroiditis，accounting for 94.12%，4.41% and 1.47%，respectively.All patients had orbital imaging suggestive of extraocularmuscle involvement.Strabismus and thyroid function abnormality appeared simultaneously in 9 cases（12 eyes），accounting for 18.75%；39 cases（56 eyes）with strabismus after thyroid function abnormality，accounting for 81.25%.None of the patients showed hyperthyroidism in their preoperative thyroid function.Strabismus patterns included vertical deviation with esotropia（32 cases，44 eyes，accounting for 66.67%），vertical deviation with exotropia（2 cases，4 eyes，accounting for 4.17%），isolated vertical deviation（8 cases，10 eyes，16.67%），and isolated esotropia（6 cases，10 eyes，accounting for 12.50%）.Orbital imaging demonstrated extraocular muscle thickening in 162 muscles across 48 patients（68 eyes）.Specifically，involvement of the inferior rectus（40 cases，61 eyes，accounting for 83.33%），superior rectus（31 cases，46 eyes，accounting for 64.58%），medial rectus（26 cases，45 eyes，accounting for 54.17%），and lateral rectus（8 cases，10 eyes，accounting for 16.67%）was observed.Multimuscular involvement（≥2 muscles）occurred in 36 cases（56 eyes，accounting for 75%），while 12 cases（12 eyes，accounting for 25%）exhibited singlemuscle involvement.Surgical intervention targeted 81 rectus muscles（78 weakened，3 strengthened）.Weakening procedures included single-muscle recession（28 cases，28 eyes，accounting for58.33%），twomuscle recession（14 cases，28 eyes，accounting for 29.17%），and multimuscular recession（6 cases，12 eyes，accounting for 12.5%）.The average preoperative intraocular pressure of 45 cases（64 eyes）was（24.19±9.26）mmHg（1 mmHg＝0.133 kPa），and the average postoperative intraocular pressure was（19.99±7.00）mmHg.The postoperative intraocular pressure decreased compared to preoperative levels，and the differencewas statistically significant（t＝5.695，P＜0.05）.The preoperative average visual acuity was（4.82±0.50）logarithm of theminimum angle of resolution（logMAR），and the postoperative average visual acuity was（4.86±0.45）logMAR.There was a significant improvement in postoperative visual acuity，and the difference was statistically significant（t＝1.995，P＜0.05）.The average preoperative protrusion degree was（19.80±2.22）mm，and the average postoperative protrusion degree was（17.60±2.14）mm.The postoperative protrusion degree decreased compared to preoperative，and the difference was statistically significant（t＝14.408，P＜0.05）.

Conclusions

TAO-induced restrictive strabismus predominantly involvesmultiple extraocularmuscles，particularly the inferior and medial rectus.Weakening procedures for restricted muscles，with adjunctive antagonist muscle strengthening when necessary，effectively restore ocular alignment and improve functional outcomes.

Key words: Thyroid-associatied ophthalmolopathy, Restrictive strabismus, Surgical treatment, Extraocularmuscle