Outcomes of the intraoperative relaxed muscle positioning technique in strabismus surgery for thyroid eye disease

ABSTRACT

Thyroid eye disease (TED) can cause incomitant strabismus with muscle restriction, resulting in diplopia and patient discomfort and discontent. Surgical correction of TED‐associated restrictive strabismus has been attempted, with fixed and adjustable suture success rates varying from 38% to 82%. This paper reviews five articles that explored the utility of the intraoperative relaxed muscle positioning (IRMP) technique in patients with restrictive strabismus due to TED. While IRMP is a useful technique for addressing TED‐related strabismus and is effective in patients with incomitant strabismus, disease reactivation, staged and unplanned surgeries, combined horizontal and vertical deviations, and previous orbital decompression surgeries, it is probable that this approach can be utilized in children with restrictive types of strabismus. Therefore, further studies are required.

The intraoperative relaxed muscle positioning technique is a useful surgical tool in treating thyroid eye disease‐related restrictive strabismus.

INTRODUCTION

Thyroid eye disease (TED) results from autoimmune activation of orbital fibroblasts, which leads to thickening and loss of elasticity of extraocular muscles and, in some patients, restrictive strabismus and diplopia. The incidence of TED has been reported at 19 per 100 000 people, ¹ with women being five times more likely to be affected than men. ¹ Restrictive myopathy was reported to occur in 40% of the affected population, ¹ along with exophthalmos, optic nerve dysfunction, eyelid retraction, lid lag, pain, diplopia, photophobia, lacrimation/photophobia, and blurred vision. ¹ Other associated findings in Graves’ disease include thyroid dermatopathy, acropathy, myasthenia gravis, and superior limbic keratoconjunctivitis. Patients with TED may be hyper‐, hypo‐, or euthyroid. ¹

Surgical correction of TED‐related strabismus can be challenging but is only necessary for 4%–7% of patients. ² , ³ , ⁴ Multiple approaches have been explored, most notably fixed and adjustable suture techniques. The outcomes of both procedures vary widely, with success rates ranging from 38% to 80% if fixed suture techniques are utilized, and 64%–82% with adjustable sutures. ⁵ , ⁶ , ⁷ , ⁸ Another approach focuses on the release of extraocular muscle restriction as the primary goal of surgery. ⁹ , ¹⁰ , ¹¹ The intraoperative relaxed muscle positioning (IRMP) technique is a variation of nonadjustable surgery that aims to release restriction of tight extraocular muscles and determine the attachment site at the time of surgery, with reported success rates ranging from 71% to 90%. ⁴ , ⁸ , ¹² , ¹³ , ¹⁴ We reviewed the current literature and explored the characteristics of patients whose outcomes were suboptimal. Although this technique and its results have only been described in adults, we suspect that it can be utilized in children with restrictive types of strabismus. Additional studies are needed to confirm this effect, particularly considering its success in adults.

METHODS

A literature review using PubMed and Google Scholar search engines was undertaken to search for the combination of keywords of “intraoperative relaxed muscle positioning technique.” The search was then refined to include only patients with TED. Five studies that met these criteria were identified. All studies were retrospective chart reviews. The original surgical technique has been described by Nicholson et al. ⁴

RESULTS

Five studies were included in this analysis. Three of the five were from the same practice location and shared the same senior author (Elias I. Traboulsi). ⁴ , ⁸ , ¹² The other two studies were from unrelated locations and authors. ¹³ , ¹⁴ All five studies were retrospective chart reviews. The number of patients analyzed varied from 8 to 129.

Preoperative patient characteristics

The average patient age for all studies was 53.3 and ranged from 20 to 85.2 years old. Approximately 60.7% of the patients were female, ranging in age from 37.5 to 79. On average, 46.1% of the patients (range: 12.5% ¹⁴ –63% ⁴ ) had prior orbital decompression. The mean number of operated muscles in the first surgery was 2.15 (range: 1.5–2.4). ⁴ , ¹² , ¹⁴ Follow‐up ranged from 1.5 to 138 months with an average of 27.01 months.

Surgical techniques

In four studies, nonadjustable sutures were used to reattach the muscle to the globe. ⁴ , ⁸ , ¹² , ¹⁴ One study used intraoperative adjustable sutures in which the patient was seated in the middle of the procedure to measure alignment and adjust the position of the insertion. ¹³ All surgeons used general anesthesia except Lekskul et al. ¹³ also used topical anesthesia in some patients and general anesthesia in others. With the variations noted above, the mainstay of the surgical approach was described in detail previously by Nicholson et al. (Table 1). ⁴ Intraoperative forced ductions were used to determine the restricted muscles and finalize the surgical plan. A fornix‐based incision was used, and meticulous clearing of the intermuscular attachments and check ligaments was performed during the procedure. The muscle was imbricated using a double‐armed 6‐0 polyglactin suture, with double‐locking bites placed at each pole of the muscle. Once the muscle was removed from the globe, repeated forced duction testing was performed to ensure that the previously noted restriction was resolved. The globe was placed with the anterior‐posterior axis perpendicular to the frontal plane, and the muscle was reattached to the sclera at a point where it rested freely around the globe. The muscle was secured using a crossed‐swords technique, and the distance from the limbus was measured with calipers. The conjunctiva was closed using polyglactin sutures. ⁴ A video detailing the procedure is provided in the Supplementary Materials.

TABLE 1.

Highlights of intraoperative relaxed muscle positioning (IRMP) technique ¹²

Step	Description
1	Intraoperative forced duction testing to determine restricted muscles and solidify the surgical plan.
2	Fornix‐based incision.
3	Meticulous clearing of intermuscular attachments and check ligaments.
4	Double‐armed suture technique with 6‐0 polyglactin suture used to secure the muscle in a double‐locking fashion.
5	Repeat forced ductions to ascertain the resolution of restriction after the muscle is removed from the globe.
6	Reattachment of the muscle to a point where it rests freely on the globe that is positioned with the anterior‐posterior axis perpendicular to the frontal plane.
7	Crossed‐swords technique for muscle reattachment and documentation of distance of muscular attachment from the limbus.
8	Conjunctiva closed with 6‐0 polyglactin sutures.

Three of the studies ⁴ , ⁸ , ¹² shared a surgical technique that emphasized the importance of preoperative and intraoperative assessment of ductions by estimating/measuring the movement of the eye in different directions in degrees ⁸ and relied on proper positioning of the eye with the anteroposterior axis lying perpendicular to the frontal plane when choosing the point of reattachment of the recessed muscle(s). ¹² Only one or two ipsilateral muscles were operated on at one time, and all surgeries were performed under general anesthesia. ⁴ , ⁸ , ¹² A similar operative technique under general anesthesia was described by Sarici et al., ¹⁴ emphasizing intraoperative forced duction testing. Lekskul et al. ¹³ modified this technique to incorporate adjustment of sutures during the intervention. Some of the patients received general anesthesia and other local anesthesia. ¹³ For adjustment under topical anesthesia, the muscle was sutured to the globe in the estimated proper position, and the patient was seated upright. A cover test was used to evaluate the eye position, which in turn guided suture adjustment. ¹³ Patients in that study were fully awoken from general anesthesia to perform the adjustment in the middle of the intervention. ¹³

Muscles operated

It has long been observed that the inferior and medial recti muscles are most commonly involved in TED, ¹ which was consistent with the authors’ experience in all reviewed papers. ⁴ , ⁸ , ¹² , ¹³ , ¹⁴ Other muscles were operated on in 21% of cases reported by Dal Canto et al., ¹² 19% of cases reported by Nicholson et al., ⁴ 20% of cases reported by Lekskul et al. ¹³ 18.9% of cases reported by Muste et al. ⁸ and none of those reported by Sarici et al. ¹⁴ Two or more muscles were operated on in 62.7% of patients (range 37.5% ¹⁴ to 79% ¹² ). Simultaneous vertical and horizontal muscle surgeries were performed in 41.2% of the patients (range 12.5% ¹⁴ to 55.6% ¹³ ). The most commonly performed procedure on more than two muscles was the simultaneous recession of both the medial and inferior recti. ⁴ , ⁸ , ¹² , ¹³ Lekskul et al. ¹³ reported the same incidence of unilateral medial and unilateral lateral rectus muscles in their study. Sarici et al. ¹⁴ observed that the most common two‐muscle procedure performed was unilateral medial and inferior rectus recessions.

Success rates and factors affecting success

The definition of surgical success adopted in all studies was described by Dal Canto et al. ⁴ , ⁸ , ¹² , ¹³ , ¹⁴ (Table 2) and was slightly adapted to include a vertical motor component by Lekskul et al. ¹³ Average success rate after a single strabismus surgery was 81.8% (range 71% ⁴ –91.6% ¹² ).

TABLE 2.

Definition of surgical success ¹²

Outcome/Characteristic	Excellent	Good	Poor
Diplopia	None in primary and reading gaze	None in primary and reading gaze	Persistent diplopia in primary or reading position; inability to tolerate prisms
Prisms	None	<10 pd	Any

Dal Canto et al. ¹² reported an overall success rate of 91.6% after one operation, which improved to 100% after two procedures. In the present study, the reoperation rate was 8%. The authors reported no statistically significant differences in success rates in patients who had undergone prior decompression or developed diplopia following decompression. ¹² There was no correlation between the amount of muscle recessed and preoperative deviation. ¹²

Nicholson et al ⁴ reported a success rate of 71% after one surgery, which increased to 90% after additional surgery. In this study, no correlation was observed between the extent of muscle recession and the preoperative angle of strabismus. ⁴ The authors did find a statistically significant increased risk for reoperation in patients who had more prior treatment modalities for strabismus (P = 0.03), larger preoperative horizontal deviations (P = 0.03), primarily horizontal strabismus (P = 0.04), or diplopia prior to orbital decompression surgery (P = 0.05). ⁴

Muste et al. ⁸ reported a 93.7% success rate. The reoperation rate was 25.6%. ⁸ Of the cohort requiring a 2nd procedure, excellent and good outcomes were achieved in 75.8% of patients, including patients with planned surgical staging, disease reactivation, and frozen globe. ⁸ Preoperative deviation did not correlate with the extent of muscle recession. ⁸ Need for additional surgical intervention correlated with disease reactivation (P < 0.001) and preoperative angle of horizontal strabismus (P = 0.037). The authors noted that success rates were similar in patients who underwent one or four muscle surgeries (P = 0.8523) and those who underwent one or two muscle surgeries (P = 0.999). ⁸ In this study, five patients underwent a third procedure and one underwent a fourth surgery. About 66.7% of reoperations involved a vertical muscle. ⁸ Prior orbital decompression did not increase the risk of reoperation (P = 0.190). ⁸ In this study, five patients had a reactivation of TED. ⁸

Lekskul et al. ¹³ categorized success rates by the number of required operations, with motor success achieved in 84.62% and sensory success in 84.62% of patients undergoing one surgery. This decreased to 81.58% (motor) and 84.21% (sensory) with two operations, 75.00% (motor) and 64.29% (sensory) with three operations, and 75.00% (motor) and 78.57% (sensory) with four operations. ¹³ The authors determined that there was no statistically significant difference in motor and sensory outcomes among these groups (P = 0.58 and P = 0.84). ¹³ There was a 7.78% reoperation rate in their study and some shared characteristics of patients requiring reoperation were male gender, smoking/second‐hand smoking, euthyroid state, multiple muscle surgery, and prior orbital decompression. ¹³ The authors did not report the statistical significance of these characteristics on how they affect reoperation rates.

Sarici et al. ¹⁴ reported success in 87.5% (all excellent) and poor outcomes in 12.5%. ¹⁴ The authors administered the Graves Ophthalmopathy‐Quality of Life test and found that the mean visual function and appearance scores increased significantly after surgery (P < 0.0001). ¹⁴

In a table summarizing the findings in seven patients requiring reoperation, Lekskul et al. ¹³ found that four (57%) had undercorrections, compared to five (13%) of the 13 patients requiring reoperation who had undercorrection of strabismus in the study by Nicholson et al. ⁴ Undercorrection was reported in two patients (50%) of four that required reoperation in Dal Canto's study. ¹² More details were given in the largest study by Muste et al. ⁸ who reported a 13% undercorrection rate in patients undergoing bilateral medial rectus recession (BMR) procedure, 14.3% in patients undergoing bilateral inferior rectus recession (BIR) and BMR, and no under or overcorrections in patients undergoing BIR.

DISCUSSION

This review presents the outcomes of patients who underwent IRMP for TED‐related strabismus repair. There were more female than male patients, as previously reported. ¹ , ⁸ , ¹³ , ¹⁵ , ¹⁶

For successful implementation of IRMP, patients should be in a quiescent stage of the disease and show stable alignment ¹⁷ and motility deficits. Orbital imaging is also a useful tool for planning surgical approach. ⁸ , ¹⁷ Preoperative imaging was not analyzed in any of the studies, although it is generally our practice to obtain MRI of the orbits in all patients with restrictive strabismus. The nature of this technique recommends using a fornix‐based approach to minimize scarring and promote faster healing.

The overall success rates of IRMP are comparable to those of adjustable and fixed sutures following dose‐response curves based on preoperative measurements. ⁶ , ¹⁶ , ¹⁸ , ¹⁹ In addition, the reviewed studies clearly demonstrate the success of IRMP in treating combined horizontal and vertical strabismus by operating on both components simultaneously. The degree of vertical deviation or combination of horizontal and vertical deviations was not predictive of failure of this procedure; however, large horizontal deviations were noted to be associated with poorer surgical success in two studies. ⁴ , ⁸ Surgical success in addressing both vertical and horizontal components of strabismus is instrumental in addressing asymmetric strabismus, which is common in patients with TED.

TED‐associated strabismus presents other unique challenges to strabismus repair, such as difficulties in addressing asymmetric strabismus, challenges of reoperations after prior surgery or disease reactivation, and the management of complex strabismus requiring staged surgeries. Low rates of under‐correction reported by the authors of these studies ⁴ , ⁸ , ¹² , ¹³ in various combinations of horizontal and vertical muscle involvement are in contrast to long‐term overcorrection rates reported in prior literature with adjustable and dose‐dependent sutures ¹⁷ , ¹⁹ , ²⁰ , ²¹ and improved compared to other reports of 38% success rates in fixed sutures ⁷ and 64% success with adjustable sutures. ⁷ The authors of some of these studies suggest that patients with TED should be left slightly under‐corrected ¹⁷ , ¹⁹ in order to achieve good long‐term alignment, but such suggestions are not made in the studies presented here. ⁴ , ⁸ , ¹² , ¹³ , ¹⁴ One study brought up concerns about decreasing success rates with simultaneous operations on multiple muscles ¹³ however this was not observed by other authors. ⁸ IRMP does not require standard dosing tables and significant postoperative manipulation of adjustable sutures which can be both uncomfortable and technically challenging but achieves comparable success rates to those reported in the literature. ⁶ , ¹⁶ , ¹⁸ , ¹⁹ In addition, evidence of successful treatment of patients with reactivation of TED ⁸ using IRMP is presented, although the authors comment on the small number of patients in this cohort and suggest further investigations to ascertain its utility.

Strabismus surgery, both with fixed and adjustable sutures, following orbital decompression has been shown to be less successful ²² in some studies ²² , ²³ , ²⁴ and as successful as in patients who have not undergone decompression surgery in other studies. ²⁵ , ²⁶ The use of IRMP did result in different success rates between the two groups in the reviewed papers. ⁴ , ⁸ , ¹² Lekskul et al. ¹³ commented that a larger number of patients who required reoperation had a history of prior orbital decompression but did not provide statistical analysis.

Factors that significantly predicted unfavorable outcomes in these studies include larger preoperative horizontal deviations, ⁴ , ⁸ disease reactivation, ⁸ multiple prior treatment modalities for TED, ⁴ primarily horizontal strabismus, ⁴ and diplopia prior to orbital decompression. ⁴ Lekskul et al. ¹³ listed factors shared by patients who needed repeat surgery, including prior decompression, male sex, exposure to smoke, and euthyroid state, but did not comment on the statistical significance of these factors in their study population.

This review is limited by the relatively small number of publications available that implemented the IRMP technique; however, the number of patients ranging from 8 to 129 constitutes a large overall sample size. All studies were retrospective in nature, which contributed to bias. Finally, no review has directly compared IRMP with adjustable or fixed suture techniques.

CONCLUSION

IRMP leads to outcomes comparable to those of the adjustable and fixed suture techniques when addressing TED‐related strabismus. It is effective in cases of asymmetric strabismus, disease reactivation, staged or unplanned secondary surgeries, combined horizontal and vertical deviations, and prior orbital decompression surgery. This procedure avoids the discomfort and technical issues associated with postoperative suture adjustment and can be performed via a fornix‐based approach that increases comfort to the patient during convalescence and reduces scar tissue formation. It is also possible that this approach can be used in children with restrictive types of strabismus. Therefore, further studies are required.

CONFLICT OF INTEREST

The authors declare no conflict of interest.

Supporting information

Supporting Information

Eisenberg MA, Traboulsi EI. Outcomes of the intraoperative relaxed muscle positioning technique in strabismus surgery for thyroid eye disease. Pediatr Investig. 2025;9:133–138. 10.1002/ped4.12467