Surgical design and efficacy for restrictive strabismus due to thyroid-associated ophthalmopathy

Patients with restrictive strabismus caused by thyroid-associated ophthalmopathy (TAO) often experience diplopia and restricted eye movements, which significantly affect patient's daily life and work. For such strabismus cases, extraocular muscle surgery is commonly performed once the primary condition stabilizes. This study aims to compare and analyze the effectiveness of 3 rectus muscle weakening procedures on the affected extraocular muscles in TAO-induced restrictive strabismus, and to summarize surgical experiences.

A retrospective analysis was conducted on 50 patients (68 eyes) with TAO-induced restrictive strabismus who were treated at the Eye Center, Xiangya Hospital, Central South University, between March 2017 and August 2023. The main target extraocular muscles causing ocular deviation and movement restrictions were subjected to either simple rectus recession (served as a recession group), rectus Y-split recession (served as a Y-split group), or modified rectus Y-split recession (served as a modified group). Postoperative observations included strabismus angle, ocular alignment, eye movement, binocular visual function, presence of diplopia, and compensatory head posture, with at least one follow-up visit (≥6 weeks).

Among the enrolled 50 patients, there were 24 males and 26 females; the affected muscles included 40 inferior rectus muscles and 28 superior rectus muscles. The patients' ages ranged from 28 to 77 years, with a surgical age of (52.9±9.5) years. The disease duration ranged from 6 months to 30 years, with postoperative follow-up periods ranging from 1.5 to 43.0 months. Significant differences in the strabismus angle were observed between preoperative and postoperative day 1, and between preoperative and final follow-up in all 3 groups (all P<0.001). In the recession group, the strabismus angle decreased by 23.52 prism diopters (PD) on postoperative day 1 and by 23.33 PD at the final follow-up. In the Y-split group, the strabismus angle decreased by 27.50 PD on the postoperative day 1 and by 28.58 PD at the final follow-up. In the modified group, the strabismus angle decreased by 35.67 PD on the postoperative day 1 and by 37.00 PD at the final follow-up. Among the 50 patients, 45 (90.0%) had preoperative diplopia, and 32 (71.1%) experienced resolution of primary and reading position diplopia at the final follow-up (χ²=42.04, P<0.001). At the final follow-up, all patients showed significant improvement in eye movement and binocular visual function, with the elimination of compensatory head posture.

Depending on the degree of extraocular muscle movement restriction in TAO patients, simple muscle recession, Y-split recession, and modified Y-split recession can be employed. These procedures can effectively relieve or improve muscle restrictions, enhance eye movement capabilities and range, eliminate ocular deviations and diplopia, and improve the visual function and quality of life for patients.