This case series retrospectively analyzed patients with cyclotorsion who underwent strabismus surgery at the Ophthalmology Department of the Tri-Service General Hospital in Taipei, Taiwan between August 2019 and August 2021. The study protocol was approved by the Institutional Review Board (No: C202105113) of the Tri-Service General Hospital. The requirement for informed consent was waived by the review board according to the guidelines for a retrospective study. All patients were followed up for at least 6 months after the surgery.

The inclusion criteria were documented cyclotorsion and surgical treatment using the proposed technique. The data collected included demographic and clinical information, diagnosis, pre- and postoperative ophthalmic and strabismus examination results, the strabismus surgery performed, and pre- and postoperative fundus photographs. Patients with incomplete information were excluded from the study.

The standard strabismus examinations included a prism alternate cover test to determine the angle of deviation in the primary and nine cardinal positions, a 3-step test, and a double Maddox rod test (DMR; Figure 1A), according to the protocol proposed by Liebermann et al. (32) to measure subjectively the cyclodeviation of the patient. Color fundus photographs (Figure 1B) were routinely acquired pre- and postoperatively to document the difference in the objective cyclodeviations, and the degree of the disc-fovea angle (DFA) was calculated using the online software Cyclocheck (33).

The procedure and surgical correction required were determined preoperatively by Dr. Chien, who performed all the strabismus surgeries under general anesthesia. All chosen surgical procedures were performed with an adjustable suture technique. The degree of cyclodeviation to correct was calculated based mainly on the subjective measurements from the DMR test, supported by the calculated objective DFA from color fundus photography (Figures 1A, B).

The proposed surgical technique for accurate intraoperative torsional adjustment is a simple marking system. First, the patient was asked to fixate directly ahead while staying in an upright head-straight position before inducing general anesthesia. With the guide of a simple toric reference marking device (Cionni Toric Reference Marker, Duckworth & Kent Ltd., Baldock, United Kingdom), the eye’s horizontal axis, parallel to the floor through the pupil, was marked using a marking pen able to withstand the disinfection procedures, preferably on the cornea, which is not affected during strabismus surgery. A horizontal line was also marked on the skin of the periocular region to add an external horizontal reference line for intraoperative adjustments. In this first step, the ocular horizontal markings and external horizontal markings should be aligned or parallel to each other. Second, the patient was placed in the supine position for anesthesia preparation and instructed to look straight ahead, alternatively with each eye if both eyes required surgery, to examine the ocular markings for significant cyclotorsion induced by postural change. If significant torsional change induced by the supine position was present, the ocular horizontal marking was updated to align or be parallel to the external horizontal markings. After the patient was anesthetized and properly draped, we ensured that the previous external and ocular horizontal markings were visible and adequate as a reference. Third, we marked the predetermined correcting degree for cyclodeviation on the ocular surface using a toric axis marking device (Cionni Toric Axis Marker, Duckworth & Kent Ltd.) with degree measurements (Figure 1C). Finally, the chosen strabismus surgery to correct any horizontal and/or vertical deviation and cyclodeviation was performed. Before the conclusion of the surgery, the surgical torsion markings were supposed to be aligned or parallel to the external horizontal markings. If the desired position was not achieved through the approach originally planned, adjustments were performed immediately to align the surgical torsion markings to the external horizontal markings (Figure 1D). Adjustments could be obtained with a modifiable suture technique or additional muscle surgery.

All postoperative data presented in Table 1 were obtained at 3 months postoperatively. Descriptive statistics were calculated using Microsoft Excel and expressed as mean (standard deviation, [SD]). The pre-and postoperative DMR and DFA were analyzed with their net value from the sum of the right and left eye.

Fifteen patients (10 male and 5 female) met the inclusion criteria and underwent surgery with the proposed marking system for torsion correction between August 2019 and August 2021. The mean (SD) age was 47.29 (28.15) years, and three patients were under 18 years (Patients 3, 7, and 15), whereas the oldest was 89 years old. Etiologies contributing to the torsional aspect of the strabismus included ischemic (n = 5) or traumatic (n = 1) trochlear nerve palsy, congenital SOP with inferior oblique overaction (IOOA) (n = 2), primary IOOA (n = 2), thyroid-associated orbitopathy (n = 1), and other types of strabismus (n = 4). The surgical approach for each case differed according to the underlying etiologies; the clinical presentations are listed in Table 1.

There were 13 cases of net exyclotorsion and 2 of net incyclotorison preoperatively. The preoperative DMR ranged from 36° of incyclotorsion to 13° of excyclotorsion. The overall mean (SD) of the preoperative net DMR was 6.0° (10.8°), and the mean (SD) DMR was 0.8° (9.3°) for the right eye and 5.2° (5.1°) for the left eye, respectively. The preoperative overall mean (SD) net DFA was 20.23° (13.21°), and the mean (SD) DFA was 7.08° (9.84°) for the right eye and 13.16° (6.13°) for the left eye. The overall mean (SD) of the postoperative net DMR was 0.2° (2.1°), and the mean (SD) DMR was 0.1° (1.8°) for the right eye and 0.1° (1.1°) for the left eye. The postoperative mean (SD) net DFA was 14.09° (5.97°), and the mean (SD) DFA was 5.98° (4.84°) and 8.11° (2.91°) for the right and left eyes, respectively. The mean absolute net DMR and DFA being treated were 9.8° (4.8°) and 9.76° (4.61°), respectively. Patients 1, 9, and 15 are discussed here to illustrate the simplicity and the advantages of this marking system for intraoperative adjustment to correct the torsion degree simultaneously with other surgical treatments, such as for vertical strabismus or IOOA.

Patient 15 was a 7-year-old boy with a significant right head tilt. Left hypertropia with 4 prism diopters and grade-2 IOOA were observed, and the 3-step test was positive for left SOP. The DMR test revealed subjective excyclotorsion of 5° in the left eye only. The objective calculated DFA from color fundus photography using Cyclocheck was 9.32° in the right eye and 14.07° in the left eye, for an overall 4.75° excyclotorsion in the left eye, consistent with the result of the subjective DMR test. Hence, a surgical 5° incyclotorsional effect was predetermined for surgical torsion marking. A 10-mm IO recession was performed to correct the primary vertical deviation, IOOA, and excyclotorsion, using the surgical markings described in the Section “Materials and methods.” Intraoperatively, the IO muscle was disinserted and repositioned on the sclera at the intended 10-mm recession position, then temporarily tied only with a slip knot for possible adjustments. The surgical effect was assessed to determine whether the recession was sufficient to align the surgical torsion marking with the external horizontal markings. The markings were aligned, and the suture was then tied securely to complete the surgery. The 3-month postoperative strabismus examination revealed orthotropia with grade-1 IOOA and no subjective torsion on DMR testing which remained stable throughout follow-up. The DFA calculated with Cyclocheck in the left color fundus photograph revealed a reduction in cyclotorsion to 4.57°compared to the preoperative DFA (Figures 2A, B).

Patient 9 was a 66-year-old male with acute vertical, and subsequent torsional, diplopia. Initial strabismus examination revealed 8 prism diopters of right hypertropia and 6 prism diopters esotropia were noted. The 3-step test was inconclusive. A diagnosis of idiopathic orbital inflammation with right superior rectus muscle hypertrophy, causing secondary strabismus was made. Medical treatment with systemic steroids was prescribed. During the treatment and observation period of 6 months, the disease was relatively quiescent, and the strabismus stabilized on a right hypertropia of 20–25 prism diopters at the simultaneous prism cover test with fusion, and 30 prism diopters on the DMR test. However, a net right incyclotorsion of 8° was also revealed by the DMR test, with symptoms under a corrected prism. The preoperative DFA was −2.86° in the right eye and 2.26° in the left eye (Figure 3A). A strabismus surgical correction was then planned with superior rectus muscle recession, using the hang-back technique, and muscle biopsy for tissue proof. The proposed torsion marking system was applied intraoperatively to monitor the torsional effect of the muscle biopsy combined with the corrective muscle-weakening procedure. Eventually, the surgical torsion marking was set approximately 8°clockwise to the external horizontal markings to correct 8° of incyclotorsion. At the 3-month follow-up, the DFA was 1.45° in the right eye and 4.61° in the left eye (Figure 3B), and the patient was orthotropic in the primary position with 1° subjective incyclotorsion in the right eye, with an incomitant esotropia and left hypotropia on downward gaze.

Patient 1 was a 49-year-old woman who suffered from intraoperative bleeding during endoscopic transnasal transphenoid removal of an invasive pituitary macroadenoma with clival involvement 5 years earlier. Postoperatively, the patient experienced a bilateral asymmetric oculomotor nerve palsy with secondary strabismus. Multiple strabismus surgeries were attempted to treat the different aspects of the ever-evolving secondary strabismus, from a marked exotropia to a consecutive esotropia, with evident right hypotropia, and a significant 40° incyclotorsion due to secondary SO overaction. However, previous attempts failed to correct the debilitating symptomatic cyclodiplopia. The patient was then referred to Dr. Chien with a constant right esotropia, hypotropia, and significant incyclotorsion measuring 27° on DMR testing and −20.54° DFA on the color fundus photographs (Figure 4A). Owing to the severe conjunctival scarring, the surgical plan was devised after meticulous dissection of the conjunctival scar tissue. Scarred muscle and scar tissue complexes were identified on the eyeball at several attachment sites and detached, then secured with 6-0 Vicryl (Ethicon, Raritan, NJ, USA) for adjustment. The surgical torsion markings were targeted for an excyclotorsion effect of 30°, marked clockwise above the horizontal reference line. Eventually, a transposition of the medial rectus muscle to the lateral side of the original inferior rectus muscle insertion was performed, with transposition of the inferior rectus muscle to the inferior side of the lateral rectus muscle. The 1-month postoperative result was temporarily satisfactory with 3° of incyclotorsion on DMR testing and −1.17° of DFA (Figure 4B). Unfortunately, after 5 months, the incyclotorsion increased to 10° on DMR testing with −5.00° DFA (Figure 4C). A second operation with transposition of the superior and lateral rectus muscle insertion was performed to correct the residual torsion. The intraoperative torsion correction was targeted to 10° excyclotorsion effect using the proposed surgical torsion marking system; however, due to the poor muscle tone and severe scarring noticed intraoperatively, the outcome was unsatisfactory, with a residual 5-10° incyclotorsion on DMR testing and −1.04° to −2.09° DFA (Figures 4D–F). After 3 months we attempted another reoperation. The residual muscles and scar tissues were temporarily fixated and adjusted solely based on the effect that could align the surgical torsion markings to the external horizontal markings. The primary surgical aim to correct the symptomatic cyclodiplopia and treat the residual horizontal and vertical strabismus using a prism was achieved. The patient had no residual cyclodiplopia one month postoperatively (Figure 4G). At the 5-month follow-up, the patient had a 4° incyclotorsion on DMR testing and 0.40° DFA, with constant right esotropia and hypotropia corrected by prism (Figure 4H). The patient was symptom-free with fusion and satisfied with the surgical outcome.