Limitation of eye movement may not always be correctable. Cranial nerve palsies, Duane’s syndrome, trauma, and other causes of restrictive strabismus may result in bothersome diplopia in important gaze positions, such as downgaze. Balancing the gaze limitation in one eye by creating a symmetrical gaze restriction in the other eye may relieve symptoms.
The simplest restrictive procedure is the anterior transposition of the inferior oblique, which predictably limits upgaze. The faden operation was designed to limit extreme gaze positions by reducing the arc of contact of the rectus muscle on the eye, but was shown to function by restricting the rectus muscle’s ability to slide within its pulley sleeve. This led to the design of the pulley posterior fixation procedure, which accomplishes the same result as the faden operation without the risk of posterior scleral sutures.
The posterior fixation procedures require strong pulley tissue adjacent to the muscle and are therefore ineffective for the lateral rectus muscle, and mildly so for the superior rectus. The newly designed tether flap procedure may theoretically overcome these obstacles, but it has only been used to date to combat the vertical oscillations of Bielschowsky’s syndrome. Orbital wall fixation of the lateral rectus has effectively corrected exotropia due to absent medial rectus function in third cranial nerve palsy.
33 Procedures to Restrict Movement
When motility is restricted in one eye, and no improvement in range of motion is attainable by any of the techniques described in Chapters 6, 28, and 35, it is sometimes necessary to create a balanced restriction in the contralateral eye to relieve diplopia or improve appearance. After alignment has been achieved in the primary position but diplopia persists in one or more directions of gaze, the goal of further surgery is to create restricted movement of the fellow eye into a specified gaze position or positions with little or no impact on central alignment. The classic procedure designed for this purpose is the faden operation. Anterior transposition of the inferior oblique (IO) remains a useful approach to create or balance an upgaze restriction. Newer approaches include pulley posterior fixation, tether flap creation, and orbital fixation. All these procedures are active procedures (Chapter 5), and require strong healing to produce and maintain their effectiveness. Nonabsorbable sutures should be considered, especially when there is evidence of weak collagen or weak healing.
33.2 Anterior Transposition of the Inferior Oblique
The anterior transposition of the IO, first reported in 1981 as a stronger method of IO weakening 1 (Chapter 8, Chapter 25), turned out to be a very useful tool to create an upgaze restriction. It converts the IO from an elevator to a depressor of the eye by shifting the insertion anteriorly to a point near the lateral border of the insertion of the inferior rectus (IR). This creates a tether, which restricts upgaze and has negligible torsional effect. 2 It is most commonly used to treat dissociated vertical deviations, but is also very useful to balance an upgaze restriction in the fellow eye. The technique is described in Section 25.3.8 (Video 25.2, Video 25.3).
33.3 Faden Operation
The faden operation was designed as a procedure to limit the full excursion of the eye in a particular direction by reducing the arc of contact of the corresponding rectus muscle on the globe. 3 , 4 This was achieved by placing a suture posteriorly in sclera and then bringing it through the muscle belly to effectively create a new muscle insertion. The procedure as originally designed was performed by disinserting the muscle, placing a scleral bite under the center of the muscle with nonabsorbable suture 12 to 14 mm behind the insertion. After the muscle was recessed, the suture was brought through the central muscle belly at that position, and then tied over the muscle, securing it to sclera. A modification of the technique, which allows posterior fixation without disinsertion, has two sutures placed through sclera also 12 to 14 mm behind the insertion, on each side of the muscle, securing the outer thirds of the muscle belly to sclera. There are several important disadvantages to each of these procedures, and this author gave them up many years ago. The scleral bites at such a posterior position are difficult and carry higher retinal risks from scleral perforation than anteriorly performed surgery. 5 , 6 Suturing through muscle belly tissue is a surgical faux pas in general surgery (Chapter 5). Muscle tissue does not contain enough collagen to support sutures, which tend to cheese-wire through the tissue. This author has observed this exact complication after the central-bite faden operations in several cases. These were observed upon reoperation due to lack of effect, and the muscle paths were found to have reverted back to their original state. The outer-edge type of faden procedures may have more holding power, as more connective tissue is present in muscle capsule at the muscle edges. Postoperative magnetic resonance imaging (MRI) scans following the edge-bite type of faden surgeries do show successful redirection of the muscle belly, maintained at least several months postoperatively. 7 Muscle necrosis due to tissue strangulation has also been observed.
Clark and Rosenbaum performed forced duction testing after faden placement during surgery and were surprised to find marked resistance to movement of the eye into the direction of action of the operated muscle. This effect was not predicted by the arc of contact model of the faden operation mechanism of action. Their group studied this effect with imaging and with cadaveric surgery, and they showed convincingly that the faden operation effect is due to the suture’s collision with the muscle’s pulley sleeve, which causes the restriction, and not due to the arc of contact theory. 7 This finding agrees with the clinical observation that lateral rectus (LR) faden operation is usually ineffective, as the LR pulley sleeve is weak.
33.4 Pulley Posterior Fixation
Once it was known that globe restriction could be achieved by preventing the muscle from telescoping through its pulley sleeve, the pulley posterior fixation technique was developed to take advantage of that principle without the risk of scleral sutures. 8 , 9 , 10 It has been advocated to reduce a high accommodative convergence/accommodation ratio, but this author has also found the procedure to be useful in most esotropic patients with accommodative components to their deviation. The posterior fixation sutures often allow the temporary removal of glasses without development of immediate esodeviation, affording these children inproved alignment control for swimming and other activities requiring glasses removal, which increases their self-esteem. It is also useful to balance the persisting abduction defect of the fellow eye after correction of a sixth cranial nerve palsy. Pulley posterior fixation requires a strong adjacent pulley, and therefore works best for the medial rectus (MR), next best for the IR, somewhat for the superior rectus (SR), and not at all for the LR muscles.
Pulley posterior fixation may be performed with or without rectus muscle recession. As it is most often performed on the MR, it is described as such here (Video 30.1). The MR is approached via fornix or limbal incision, and recession is performed in standard fashion (Chapter 23), with minimal or no posterior muscle dissection in order to preserve the pulley sleeve. A Stevens tenotomy hook is placed flat over the muscle belly and slid posteriorly about 10 mm. The tip of the hook is then rotated outward toward the orbital wall and then anteriorly, with gentle but steady outward force, which lifts the pulley onto the hook and brings it into the operative field (Fig. 33‑1). The assistant then retracts overlying capsular tissue posteriorly with a toothed forceps or another small hook, to expose the tip of the hook that is lifting the pulley (Fig. 33‑2). The surgeon then passes a nonabsorbable suture (6–0 polybutester or 5–0 polypropylene is recommended) through the pulley, with a backhand-loaded needle (Fig. 33‑3, Box 33.1). Maintain pulley support with the hook until the needle tip has been retrieved (Fig. 33‑4), to prevent retraction of the needle into the orbit. If this happens, back the suture out, and repeat the steps. The suture is then loaded forehand, and placed though the upper third of the muscle belly (Fig. 33‑5) adjacent to the point where it enters its pulley sleeve, usually about 10 mm from the original insertion, and the suture is tied (Fig. 33‑6), which secures the muscle to its pulley. This process is then repeated for the inferior third of the muscle belly. Forced duction is performed, which should confirm resistance of the eye to adduction.
Sutures recommended for pulley posterior fixation.
6–0 polybutester single-armed suture with SS-24 spatulated needle (Novafil Covidien Products, Medtronic, Corp).
5–0 polypropylene single-armed suture with PC-1 needle. needle (Prolene, Ethicon Corp).
Sutures recommended for tether flap.
6–0 braided polyester, double armed, on an S-28 needle (Mersilene, Ethicon Corp).
6–0 braided polyester, double armed, on an SS-28 needle (Surgidac, Coviden.).
Sutures recommended for orbital fixation.
6–0 polypropylene with C-1 taper point needle.
6–0 braided polyester.