5.1 Goals

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  Improve the short- and long-term outcomes of strabismus surgery by reducing undercorrections and overcorrections.

  
  
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  Decrease the risk of requiring additional surgery.

5.2 Advantages

Strabismus surgery outcomes are dependent not only on the surgeon and amount of surgery, but also on the patient’s potential for fusion and healing of the muscle(s). For cases that may be less predictable due to prior surgeries and abnormalities of the extraocular muscles or orbit, the adjustable suture technique is a useful option to modify the position of the muscles before healing of the surgical site. While the adjustable suture technique requires additional time in the operating room and during adjustment, the added effort may be offset if additional surgery is avoided. ¹

The adjustable sliding noose technique allows the surgeon to more easily gauge the amount of adjustment done, if needed, compared to the bowtie slipknot technique. For the bowtie slipknot technique, the muscle is reinserted, and then the muscle suture is tied in a half-bowtie, which can be untied for adjustment if needed or pulled through into a square knot to secure the position of the muscle. The bowtie slipknot technique is suitable for intraoperative adjustment of superior oblique surgery. The adjustable sliding noose technique has variations including a removable noose, which uses a clove hitch with three slip knots and can be removed from the muscle suture ² to lessen the amount of buried suture at the conclusion of surgery. The short tag noose uses a shorter adjustable sliding noose, which is buried under the conjunctiva, so that immediate or delayed adjustment is possible. ³ For the short tag noose technique, if no adjustment is required, the buried sutures, including the short tag noose, remain untouched postoperatively. In patients with robust Tenon’s capsule, isolating and adjusting the short tag noose on the muscle suture can be challenging.

5.3 Expectations

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  Adjustments should be able to be performed without difficulty or significant patient discomfort.

  
  
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  In the pediatric population, the adjustable suture technique can be considered in some teenage patients with topical anesthesia, but for most children, brief sedation, usually with propofol, is required. ⁴ If repeat sedation is required, the clinical location for adjustment depends on the surgical center and may be done in the post-anesthesia care unit or after returning to the operating room.

  
  
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  Once the position of the muscle is finalized, with or without adjustment, postoperative healing should be similar to nonadjustable strabismus surgery.

5.4 Key Principles

The adjustable suture technique can be used for all four rectus muscles by performing the surgery with the patient under general anesthesia and evaluating the alignment after the patient has awoken from anesthesia. The basic principles of the hangback technique are used with placement of the muscle suture at the original insertion in most cases for both recessions and resections. All the operative rectus muscles may be placed on adjustable sutures, or one muscle may be selected for adjustable suture placement, usually the muscle on the deviating or nondominant eye, or the muscle that has been recessed. Adjustable sutures are not used for the inferior oblique muscle due to its posterior location. Adjustable sutures can be used for certain superior oblique procedures with intraoperative adjustment based on forced duction testing and fundus torsion.

Recommended instruments for performing strabismus surgery adjustments are listed in Table 5.1. An assistant is also needed during adjustments.

5.5 Indications

Some strabismus surgeons offer the adjustable suture technique for all patients, while some reserve the adjustable suture technique for complex cases, including:

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  Reoperations.

  
  
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  Dysinnervation syndromes, such as Duane syndrome.

  
  
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  Cranial nerve palsies.

  
  
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  Restrictive strabismus.

  
  
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  Orbital anomalies.

5.6 Contraindications

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  Patients who are at high risk of anesthesia complications if sedation is required for adjustment.

  
  
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  Patient and family preference for nonadjustable strabismus surgery.

  
  
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  Patients, including teenagers, who are unlikely to tolerate adjustment with topical anesthesia, if repeat sedation is not established at the surgical center.

5.7 Preoperative Preparation

To help determine if a patient will tolerate adjustment with topical anesthesia, the technique is discussed with the patient’s family and also with pediatric patients who are able to assent to surgery. The patient’s tolerance of eye drop administration in the office can be assessed first. If eye drops are well-tolerated, a topical anesthetic is instilled and the conjunctiva is gently touched and moved over the sclera with a cotton-tip applicator. If this is well-tolerated by the patient, the patient may tolerate adjustable strabismus surgery with topical anesthesia, although the sensations during adjustment are notably different. If this is not well-tolerated by the patient, or it is otherwise determined that the patient will not tolerate adjustable strabismus surgery which is otherwise indicated for the condition, a plan for repeat sedation can be discussed with the anesthesiologist preoperatively. In some cases, nonadjustable strabismus surgery may be planned instead, with the understanding that additional surgery may be needed, especially for complex cases.

5.8 Operative Technique

The conjunctival incision, isolation, and imbrication of the rectus muscle for recession or resection are described in Chapters 3 and 4. The following are the subsequent steps for adjustable suture placement using an adjustable sliding noose:

1. 
   

   Once the operative muscle has been imbricated and then disinserted or resected, the ends of the muscle suture are held up to identify the poles of the muscles with their respective needles. One end is chosen and the needle loaded on a needle holder near its center. The insertion is securely grasped with toothed forceps. The tip of the needle is then oriented tangential to and pointed slightly away from the sclera. The needle is engaged partial thickness in the sclera at one pole of the original insertion or with vertical displacement if planned for pattern strabismus or a small vertical deviation. The needle may enter the sclera nearly at the base of the small ridge at the original insertion, and then carefully advanced partial thickness anteriorly, ensuring that the needle is visible along the entire scleral tract without being too shallow. The path of the needle may be directed toward the center of the area anterior to the insertion or perpendicular to the insertion.

   
   
2. 
   

   The above step is repeated for the opposite pole of the muscle. The exit points of both sutures anterior to the insertion should be 1 to 2 mm apart, either by using a modified crossed-swords technique or parallel scleral passes in close proximity to each other (Fig. 5.1). If the ends of the muscle suture are too widely spaced, the adjustable sliding noose will not slide easily along the muscle suture, especially when the muscle is pulled up to the insertion, such as for a resection.

   
   
3. 
   

   The two ends of the muscle suture are tied together in an overhand knot using an empty needle holder (Fig. 5.2), leaving ample length of suture between the muscle and the knot for later adjustment and final tying of the suture. The tails of the suture distal to the knot should also be of adequate length to use as the adjustable sliding noose.

   
   
4. 
   

   The tails are trimmed, and then the needle is trimmed off one remnant of the polyglactin suture. The assistant holds the muscle suture taut across the eye with an empty needle holder, being careful not to drag the suture on the cornea. The surgeon uses two additional empty needle holders to tuck the suture remnant between the muscle suture and insertion site (Fig. 5.3), and then to wrap the suture remnant two full rotations around the muscle suture. The assistant may hold one end of the adjustable suture to prevent it from unraveling during this step. The suture remnant is then tied with a 1–1 throw square knot (Fig. 5.4) with sufficient tightness for the sliding noose to remain in position without sliding too loosely but also not excessively tight so that it is difficult to slide the noose along the muscle suture during adjustment. The assistant continues to hold the muscle suture taut. The ends of the adjustable sliding noose can be brought together by placing the two needle holders around the ends of the adjustable noose at a 90-degree angle (Fig. 5.5), and then the ends are tied in an overhand knot to more easily grasp both ends of the adjustable noose during adjustment. One end of the adjustable noose is trimmed short and one left moderately long to easily distinguish between the adjustable sliding noose and the muscle suture during adjustment.

   
   
5. 
   

   For a recession, the muscle is first pulled up to the insertion by both ends of the muscle suture. Calipers set at the planned amount of recession are used to measure from the insertion, along the length of suture toward the needles (Fig. 5.6). The adjustable sliding noose is slid to the distal tip of the calipers by holding the adjustable noose with one needle holder and the muscle suture with a second needle holder (Fig. 5.7). The insertion is then grasped to rotate the globe away from the muscle so that the muscle hangs back. A needle holder can also be used to pull the sutures posteriorly through the scleral tunnels if needed. The planned amount of recession is confirmed with calipers.

   
   
6. 
   

   For a resection, the muscle is pulled up to the insertion, and the adjustable sliding noose is adjusted to be at or near the insertion on the muscle suture. A small amount of recession may be incorporated into the surgical plan for a resection to provide room for additional tightening during adjustment if needed.

   
   
7. 
   

   Next, a single-armed polyester nonabsorbable suture, which is usually white to easily distinguish from the violet polyglactin suture, is placed on the side of the insertion and muscle suture away from the conjunctival incision, to be used as a traction suture during adjustment and to aid exposure of the adjustable sutures during adjustment (Fig. 5.8). For example, for an inferiorly placed conjunctival incision, the traction suture is placed at the insertion superior to the muscle suture with a partial-thickness pass perpendicular to the insertion while securely grasping the insertion with toothed forceps. An optional second pass of the traction suture for improved traction and exposure can be placed as follows: the ends of the muscle suture and the adjustable noose are tucked away from the sclera anterior to the insertion, where a second partial-thickness pass is placed, this time parallel to the insertion. The ends of the traction suture are gathered with the central loop if the second pass is made, and tied together in an overhand knot (Fig. 5.9). The needle is trimmed.

   
   
8. 
   

   Once the muscle and sutures are in good position, the conjunctival incision is reapproximated to partially cover the adjustable sutures.

   
   
9. 
   

   At the conclusion of surgery, the sutures are taped with one or two 0.5-inch strips of paper tape, either on the nasal bridge for a nasally located conjunctival incision or on the temple for a temporally located conjunctival incision, after cleaning and drying the patient’s skin (Fig. 5.10). The sutures can be gathered onto a small area on the skin with a needle holder.

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