Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Strabismus and Amblyopia_Wright, Spiegel, Thompson_2006

possible if the muscle is tight and contracted, as in the case of thyroid-associated strabismus, congenital fibrosis syndrome, or a slipped muscle. Indications for hang-back recessions include a recession over a retinal buckle, recession over an area of scleral ectasia, or large recessions, of a tight contracted muscle, if posterior exposure is difficult. However, for routine strabismus surgery, the author (K.W.W.) prefers the fixed recession so the muscle is secured at the desired recession point.

Adjustable Suture Technique

Adjustable suture techniques allow movement of the muscle position after surgery when the patient is fully awake and the anesthesia has dissipated (Fig. 11-6). Unlike fixed sutures, the adjustable suture technique allows for fine-tuning of ocular alignment in the immediate postoperative period. The adjustable suture procedure is usually performed on recessions in two stages: in the first stage, surgery is performed under either local or general anesthesia, and the muscle is placed on a suture in such a way that the muscle position can be adjusted later. The second stage, or adjustment phase, is performed when the patient is fully awake or after the local anesthetic has worn off (5 h for lidocaine) and the muscle function has returned to normal. In this phase, the muscle is adjusted to properly align the eyes and then permanently tied in place. The adjustment procedure must be performed within 24 to 48 h after the initial surgery while the muscle is still freely mobile. Later adjustments have not been recommended because the muscle rapidly adheres to the globe. However, successful in-office reoperation within the first week of surgery has been described.5 The muscle is sutured like a hang-back recession, but the suture is tied in a bowknot or secured by a sliding noose so the position of the

FIGURE 11-6A–C. (A) Bow tie adjustable suture technique. After the sutures have been passed through the scleral insertion, they are tied together in a single-loop bow tie. This bow tie can be untied postoperatively to adjust the muscle. (B) Noose adjustable suture. Sutures suspend the muscle posteriorly, and a noose around the sutures slides up and down to secure the muscle at the desired position. The ocular alignment is finetuned with the patient awake. The muscle placement is finalized by tying off the pole sutures, then trimming all loose sutures. (C) Companion photograph of (B) shows adjustable suture through fornix, with scleral traction suture holding the conjunctiva superiorly and exposing the adjustable suture.

muscle can be easily changed (Fig. 11-6A–C). Adjustable sutures have limitations similar to hang-back recessions, with the maximum recession approximately 6 to 7 mm. Central sag occurs but, because the muscle position can be changed after surgery, this is usually not an issue. Plan on a slight overcorrection, as advancing an over-recessed muscle is easier than trying to increase the recession, especially if the recession is greater than 6 to 7 mm.

The most important indication for an adjustable suture is complicated strabismus, including paralytic strabismus, largeangle strabismus, reoperations, and thyroid myopathy. In these situations, the standard tables for surgical measurements do not apply, and results with the fixed-suture technique are unpredictable. In addition to the more complicated strabismus cases, many surgeons routinely use adjustable sutures on most cooperative adult patients, even those undergoing uncomplicated, horizontal surgery. Adjustable sutures are usually used with recession procedures, as adjustable tightening procedures are difficult to perform.

Patient selection is crucial for successful implementation of the adjustable suture technique. The adjustment procedure is somewhat uncomfortable and can evoke substantial anxiety. There is no specific age limitation for the use of adjustable sutures, but patients younger than 15 years of age are often too anxious about medical procedures. Unless a child is exceptionally calm and cooperative, adjustable sutures should be limited to cooperative adult patients. Strong sedatives before adjustment should be avoided because sedation influences eye position. The patient should wear full optical correction when ocular alignment is being assessed during the adjustment procedure to ensure proper image clarity and control of accommodation.

MUSCLE SHORTENING PROCEDURES

Muscle shortening procedures include muscle resections, tucks, and plications. These procedures tighten the muscle, but they do not actually strengthen the muscle. For the most part, they correct strabismus by creating a tight muscle that acts like a leash or tether. These procedures produce incomitance, as the tightened muscle restricts rotation away from the shortened muscle (Fig. 11-7). For example, a right medial rectus shortening procedure limits abduction of the right eye and creates an

A B C

FIGURE 11-7A–C. Effect of a rectus muscle resection (shaded muscle). The resection has its greatest effect on gaze away from the resection. (A) The muscle tightens on gaze away from the resected muscle. (B) A resected rectus muscle. (C) The muscle slackens on gaze to the resected muscle.

esodeviation shift that increases in rightgaze. Right medial rectus tightening would be indicated to correct an incomitant exotropia that is greater in rightgaze. Note that tightening the medial rectus muscle does not strengthen adduction but instead limits abduction. Bilateral medial rectus resections limit divergence and induce an esodeviation greater for distance fixation; therefore, it is not the answer for convergence insufficiency.

Resection

A muscle resection consists of tightening a muscle by removing the anterior part of the muscle and reattaching the shortened muscle to the original insertion site. The muscle resection is the most popular tightening procedure and is performed on rectus muscles.

Tuck

A muscle tuck shortens the muscle by folding the muscle and suturing the folded muscle to muscle. The muscle tuck has, for the most part, fallen out of favor partially because the muscle- to-muscle suturing does not hold well and tends to become cheese-wire loose over time. A superior oblique tendon tuck or plication, however, is used for some cases of superior oblique

palsy, either as a full-tendon plication or plication of the anterior tendon fibers (i.e., Harada–Ito procedure).

Wright Plication

The author (K.W.W.) developed a rectus muscle plication procedure that tightens the muscle by folding the muscle and suturing it to sclera (Fig. 11-8).14,18 With the plication, the muscle is sutured to the scleral insertion, in contrast to a tuck, where muscle is sutured to muscle. The muscle–scleral attachment of

A

B

FIGURE 11-8A,B. Wright rectus muscle plication. (A) The muscle is secured with the suture placed posterior to the insertion at the desired plication point (usually 6 mm or less). Once the posterior muscle is secured, the suture ends are passed through the scleral insertion. The drawing shows the suture secured to the posterior muscle and the doublearmed needles being passed at the scleral insertion. (B) The plication is completed with the posterior muscle advanced to the insertion. There is a small roll of redundant tendon that will flatten and disappear 3 to 4 weeks after surgery.

the plication is more secure than the muscle-to-muscle union of a tuck.

The plication can be used in place of a standard resection. Because there is a fold of tendon associated with the plication, a small lump is present immediately after surgery but disappears within 3 to 4 weeks. Important advantages of the plication procedure over resection include reversibility. A plication can be removed by simply cutting and removing the suture within 2 days of the surgery, before the muscle heals to sclera. Another advantage is safety against a lost muscle. Because the muscle is not disinserted, there is little risk of a lost muscle. The plication procedure also preserves the anterior ciliary vessels and reduces the risk of anterior segment ischemia. These advantages have made the Wright plication popular for small or mediumsized rectus muscle tightening surgeries.

RECESSION AND RESECTION

Resections (or plications) of rectus muscles can be teamed with a recession of the antagonist muscle same eye to correct strabismus. This monocular surgery is called a recession–resection, or “R & R,” procedure. The effect of the recession–resection of agonist and antagonist induces incomitance and limits ocular rotation in one direction. For example, a right lateral rectus muscle recession reduces ocular rotation to the right, and a resection of the right medial rectus muscle also restricts rotation to the right. Limited rotations after an R & R procedure may improve over several months to years, but some residual incomitance often persists. Because the R & R procedure induces incomitance, it can be used to treat incomitant strabismus. It is also useful in treating sensory strabismus, allowing monocular surgery to be performed only on the amblyopic eye and sparing surgery to the good eye.

FADEN

The Faden procedure is performed by suturing the rectus muscle to sclera, 12 to 14 mm posterior to the rectus muscle insertion. This technique pins the rectus muscle to the sclera so, when the eye rotates toward the fadened muscle, the arc of contact cannot unravel. As a result, the moment arm shortens, thus reducing