The muscle is secured with suture that is sufficiently strong to withstand postoperative manipulation.
The muscle is attached to the globe usually at the muscle’s insertion stump in a ‘hang loose’ manner.
The suture anchoring the muscle is secured in a way that it can be easily loosened and then re-tied at the time of adjustment.
The suture is able to slide through the site of attachment to the globe allowing the muscle to slide back or be pulled forward.
The incision in conjunctiva should be made so that the surgeon can access the suture at the time of adjustment and then close the conjunctiva satisfactorily with the patient awake.
The use of adjustable sutures are effectively limited to the rectus muscles (Figure 1).
A The muscle is exposed.
B The suture is placed 1 to 1.5 mm from the insertion (a ‘handle-suture’ as shown in Figure 2 is placed in all cases).
C The suture is secured with a central bite which is tied and locking loops are placed at the borders.
D If the muscle is tight, it is cut from the globe with a scalpel, cutting against a muscle; otherwise scissors are used.
E The sutures are brought through the muscle’s stump.
F If a bolster is used, the suture is brought through after putting the needles through conjunctiva to produce a conjunctival recession (as shown) or through conjunctiva overlying the stump.
G The suture is tied over the bolster (if used) or on conjunctiva.
In every case of adjustable suture, a so-called ‘handle suture’ is placed in superficial sclera usually near the limbus. This is used for stabilizing the eye, securing the muscle, and in rotating it at the time of adjustment. The suture can be temporarily tied with a bow know, a slip knot, or a ‘noose like’ cinch knot that can be secured tightly or loosened to slide up and down the suture as needed during adjustment.
Use of an adjustable suture begs the question, “Where should the eyes be placed at the time of adjustment?”. While there is no reliable answer to this question, I tend to leave the eyes in the alignment I would like to achieve at the same period postoperatively if the muscle had been firmly attached to sclera at the time of operation. Patients with postoperative diplopia are adjusted to a diplopiafree position. Non-fusing exotropic patients are left straight or slightly exotropic; non-fusing esotropic patients are left straight or slightly esotropic. Because I never use an adjustable suture in a patient treated surgically for intermittent esotropia, I can only suggest leaving the eye in the same alignment that is preferred when standard surgery is performed; that is, a slight overcorrection.
A ‘handle’ of 6-0 Vicryl placed in sclera at the limbus as a means of grasping and manipulating the globe during adjustment is shown in Figure 2. The ‘handle’ must be exposed at the conclusion of surgery regardless of which type of incision has been used. A forceps grasping the handle allows relatively easy rotation and stabilization of the globe during surgery and during adjustment. A three-cornered limbal incision may be used that can be taken down at the time of adjustment and repaired when the adjustment is completed. A sliding knot over the sutures suspending the muscle can be helpful during adjustment. The sliding knot is secured at surgery when the muscle is at the intended position and the suture ends are tied. At adjustment, the knot may be loosened and slid toward the cornea while the patient looks in the opposite direction as the globe is stabilized with the handle suture if the recession effect is to be increased. If the recession effect is to be lessened, the suture holding the muscle is pulled up and the slip knot is slid toward the muscle. When a cul-de-sac incision is used, a handle suture is placed at the upper insertion in case of an inferiorly placed incision. For adjustment, this suture is pulled up to center the incision over the muscle stump.
A The ‘handle’ suture.
B The suture ends must be retrievable.
C The handle suture stabilizes the globe during adjustment.
D A ‘three cornered’ limbal incision may be used.
E The sutures may be secured with a slip knot.
F The amount of ‘hang back’ can be measured.
G The muscle is advanced or it drops back sliding through the slip knot which is tightened when the muscle is in the intended position.
H Both the handle suture and the adjustable suture are led out through the cul-de-sac (inferior) incision shown.
I The handle suture lifts the incision over the muscle insertion.