Silicone band loop myopexy for myopic strabismus fixus.

Myopic strabismus fixus causes inability of the eye to elevate and abduct in the setting of a myopic superotemporally herniated globe. We report a novel surgical technique to manage an 18-year-old male with myopic strabismus fixus. Radiological imaging demonstrated a nasally deviated superior rectus (SR) and inferiorly displaced lateral rectus (LR). Silicone band assisted myopexy of SR and LR was done along with anchoring them to the sclera with a dacron suture. The patient had satisfactory alignment postoperatively and did not require any intervention over 1-year follow-up.

Myopic strabismus fixus (SF) is characterized by an eye fixed in esotropia and hypotropia with inability to abduct and supraduct the eye.[12] Pathophysiology of SF is postulated to be due to abnormalities in paths of SR and LR due to posterior herniation of the globe in the superotemporal quadrant.[13] Because of the gross undercorrection and recurrence after standard recess and resect procedures,[45] partial or complete muscle belly union of the SR and LR is now the current surgery of choice for these patients.[56]

Case Report

An 18-year-old male presented with complaints of inward deviation of his left eye (LE) for 10 years. He gave a history of use of high-powered minus power spectacles since early childhood. He denied any history of diplopia or trauma as an inciting cause. Family history was unremarkable. He had been subjected to the right eye (RE) patching, in view of the LE amblyopia, for 3 years which was gradually tapered in view of no further improvement. On examination, his best-corrected visual acuity was 6/12 RE (−19.0 DS) and 6/60 LE (−18.0 DS). His LE was fixed in adduction and depression with inability to abduct (−5) and elevate (−4) beyond the midline. He had a 62 prism diopter (PD) esotropia and 10 PD hypotropia in the LE with glasses [Fig. 1a and b]. Sensory evaluation revealed LE suppression with absent gross stereopsis. Extraocular movements in the RE were full and free.

Figure 1

Gross photograph of the patient at presentation (a). There was an esotropia of 62 prism diopter (PD) in the primary position and 10 PD hypotropia with limited elevation and abduction (b). (c) Computerized tomography scan of the patient showing in-turned globe with superotemporal herniation in the left eye. Note the nasalization of superior rectus and inferior displacement of lateral rectus as compared to the right eye in reference to a horizontal line white arrows in (d)

Ancillary investigations revealed an axial length of 32.30 mm in his RE and 36.50 mm in the LE. A clinical diagnosis of myopic SF (esotropia–hypotropia complex) was made. Magnetic resonance imaging (MRI) of the orbits was advised, however, it could not be done as the patient was claustrophobic. Computerized tomography (CT) of the orbits revealed classic findings of nasalization of the SR and downward displacement of the LR [Fig. 1c and d]. A surgical plan was made to approximate the SR and LR muscle and augment the surgery with medial rectus (MR) recession if needed.

Surgical Technique

Under general anesthesia, a perilimbal conjunctival incision was made from 12 to 3 o’clock and was extended radially. SR and LR were hooked and isolated from the surrounding fascia and bridled with 4-0 silk suture. Nasalization of SR and inferior displacement of LR was confirmed intraoperatively. No evidence of atrophy either the SR or LR was seen. A silicone band type 240 was fixed to the sclera in the superotemporal quadrant with a 5-0 dacron mattress suture, 14 mm from the limbus. The band was then passed under the SR and LR, tightened, and ligated so as to approximate both the muscles [Fig. 2a and b]. The ends of the redundant band were trimmed, and conjunctiva was closed with 8-0 vicryl interrupted sutures. Forced duction testing was free at the end of surgery so MR recession was not performed.

Figure 2

(a and c) Intraoperative photograph of the deviated superior rectus (SR) and lateral rectus (LR) from the surgeons’ view (sitting superiorly) approximated with a 240 silicone band tied to the sclera (blue arrow in a). Postoperative nine gaze picture with improved abduction and elevation (b). Repeat imaging at 1 year revealed reduced displacement of the SR and LR with hyperdensity superotemporally corroborating with the location of the silicone band (d)

Postoperatively, the patient had 6 PD esotropia in primary position with improved abduction (−3) and elevation (−2) [Fig. 2c]. The patient did not complain of any postoperative diplopia. At 1-year follow up, he was maintaining alignment in primary gaze with CT scan showing approximated SR and LR [Fig. 2d].

Discussion

The efficacy of suture myopexy in myopic SF is well established.[456] Owing to complications like cheese wiring of the suture, risk of anterior segment ischemia, and irreversibility of the procedure; search for alternative materials for muscle union has been ongoing. A modified loop myopexy with 240 silicone band and scleral fixation has been found to work effectively.[7] It improves ocular alignment as well as extraocular motility in a similar fashion to suture loop myopexy.

Our technique is a modification of the silicone band assisted loop myopexy. We advocate limbal incisions to provide greater ease while operating on the widely displaced SR and LR along with use of a silicone band. The gap between SR and LR is too huge and the suture may not hold that much. Silicone band on the other hand has no risk of breaking and has excellent elasticity. Silicone material does not allow tissue in-growth and can be easily removed, if necessary, without causing scleral erosion. We also fixed the band to the sclera in a similar fashion in which encircling bands are fixed in retinal detachments. Scleral fixation has an additional advantage as it prevents migration of the silicone band. As compared to other techniques of scleral fixation; our technique has a lower risk of scleral perforation and does not require the need for special instrumentation or expertise to carve a scleral tunnel. We did not use any sleeve which might be responsible for the foreign body sensation to the patient and band removal as reported previously.[7] In addition, it is efficient, time saving, and offers all the advantages of tunnel scleral fixation.

The effectiveness of silicone band assisted loop myopexy without MR recession, in terms of surgical dosage is debatable. As compared to the results of Shenoy et al.,[7] where authors infer that loop myopexy with scleral fixation effectively corrects around 40 PD of esotropia; we reduced an esotropia of >50 PD in our patient. The wide range of correction achieved in their cohort along with our result means that either the procedure is self-regulating and adjustable, depending on the degree of restriction induced by the altered paths of the SR and LR in individual cases or the tightening achieved is much more with our technique. We did not use a sleeve as used in cases by Shenoy et al.;[7] so as to prevent a late slippage and hence undercorrection in long term.

Scleral fixation is debated to increase the risk of perforation in these myopic eyes. We took the help of an experienced retinal surgeon to fix the band to sclera. We believe the advantages offered by scleral fixation outweigh the potential risk of scleral perforation that can happen in these patients. There is however a small risk of a temporal bulge produced by the folded scleral band. It was cosmetically acceptable to our patient.

Conclusion

In conclusion, our technique is a practical surgical option for uniting the SR and LR muscles thus improving ocular alignment and motility in cases of myopic SF with deviated superior and lateral recti. Given the shorter scleral pass than typical silicone sleeve fixation techniques, our technique may have a better safety profile.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.