Ординатура / Офтальмология / Английские материалы / Strabismus Surgery and Its Complications_Coats, Olitsky_2007

Fig. 8.21a,b. Closure of a limbal incision. a The true corners of the conjunctival flap (arrowhead) can be best identified by placing traction on the underlying Tenon’s fascia near the edges of the flap. b The conjunctival flap is then sutured back to the limbus with absorbable suture

in the corners of the conjunctival flap and suturing them to the conjunctiva adjacent to the muscle insertion (>Fig. 8.23a). Some surgeons also prefer to place a suture in the middle of the conjunctival flap to secure it to the underlying insertion, though this step is not always necessary unless significant posterior sagging of the flap is present. Recession of the limbal flap is also frequently done to facilitate access to adjustable sutures postoperatively (>Fig. 8.23b).

8.2.3Converting a Fornix Incision into a Limbal Incision

Occasionally the surgeon finds it necessary to convert a fornix incision into a limbal incision after surgery has begun.

Fig. 8.22. Modified limbal incision. For most simple rectus muscle operations some surgeons create a two-sided incision, eliminating one of the radial incisions

Indications for conversion may include inadequate exposure of the surgical site, bleeding, and complications that may be best managed with the additional exposure of the surgical site afforded by a limbal incision. Conversion can be easily accomplished with a few simple steps.

8.2.3.1 Technique

The end of the fornix incision nearest the limbus is extended to the limbus (>Fig. 8.24). The incision is then carried along the limbus and a radial incision made in the adjacent conjunctival quadrant (>Fig. 8.24). Closure may require additional sutures along the original fornix incision to reduce the risk of protrusion of Tenon’s capsule through the wound postoperatively.

This additional suture(s) is often placed prior to converting the fornix incision into a limbal incision.

8.2.4 Swan “Over the Muscle” Incision

The Swan incision [7, 8] is described here primarily for historical interest and is rarely used today. Many surgeons feel that the Swan over the muscle technique is more likely to be associated with complications compared to other surgical approaches. Copious bleeding can occur if the conjunctival incision is too deep and enters the muscle. Damage to the muscle itself is more likely to occur during several steps of the procedure, compared with other techniques. Additionally, visible

conjunctival scarring in the palpebral fissure can be cosmetically more objectionable compared with that which occurs with other surgical approaches. Finally, surgical access to the muscle for reoperations is rendered more difficult due to extensive scarring around the muscle.

8.2.4.1 Technique

The globe is retracted to expose the conjunctiva over the muscle to be operated. A conjunctival incision is made over the rectus muscle to be operated concentric with the limbus and just anterior to the cul-de-sac (>Fig. 8.25a). For medial rectus muscle surgery, the incision is made 1–2 mm anterior to

the plica semilunaris. The incision must be made through the conjunctiva only to avoid extending the incision through Tenon’s capsule and into the muscle, which can result in extensive bleeding and/or damage to the muscle. Next, the conjunctiva is reflected anteriorly to expose Tenon’s fascia anterior to the muscle insertion (>Fig. 8.25b). The intermuscular septum is then identified, grasped with forceps, and incised to expose the underlying sclera (>Fig. 8.25c). A muscle hook is then passed to isolate the rectus muscle. The intermuscular septum on the opposite side of the rectus muscle is then incised (>Fig. 8.25d)

Fig. 8.25a–e. Swan incision, demonstrated primarily for historical interest. a A conjunctival incision is made over the rectus muscle, and b the conjunctiva is reflected anteriorly to expose Tenon’s fascia anterior to the muscle insertion c The intramuscular septum is incised. d The intermuscular septum on the opposite side of the muscle is then incised exposing the toe of the hook. The muscle is then recessed or resected without separating the muscle from the overlying muscle capsule or the adjacent intermuscular septum.

Fig. 8.25a–e. (continued) Swan incision, demonstrated primarily for historical interest. e The conjunctiva is then closed with an interrupted or running suture

allowing the toe of the hook to be visualized. Without further dissection, the muscle is then recessed or resected without separating the muscle from the overlying muscle capsule and intermuscular septum. The conjunctiva is then closed with an interrupted or running suture (>Fig. 8.25e).

8.3Conjunctival Incisions for Oblique Surgery

Surgery on the inferior oblique muscles is almost always performed through a fornix incision, though a limbal incision may be used. A conjunctival incision for oblique muscle surgery is

made in the oblique conjunctival quadrant adjacent to that aspect of the muscle or tendon to which the surgeon requires access. The incisions are similar in size and placement to fornix incisions made for rectus muscle surgery, though some surgeons prefer to place the incision more posteriorly. If a limbal incision has been used to access the inferior rectus or lateral rectus muscle, the inferior oblique muscle is often approached through the same limbal incision. Because identification and isolation of the superior oblique tendon can sometimes be difficult, some surgeons prefer to approach the superior oblique tendon through a limbal incision. When a limbal approach is desired, an incision is created similar to that which is created for access to the superior rectus muscle.

References

1.Coats DK, Paysse EA (1997) Intraoperative traction testing to detect incomplete inferior oblique myotomy/myectomy. J AAPOS 1:197–200

2.Guyton DL (1981) Exaggerated traction test for the oblique muscles. Ophthalmology 88:1035–1040

3.Plager DA (1990) Traction testing in superior oblique palsy. J Pediatr Ophthalmol Strabismus 27:136–140

4.Apers R, De Clippeleir L, Van Lammeren M (1989) Basic principles for strabismus reinterventions. Bull Soc Belge Ophtalmol 232:53–60

5.von Noorden GK (1968) The limbal approach to surgery of the rectus muscles. Arch Ophthalmol 80:94–97

6.Parks MM (1968) Fornix incision for horizontal rectus muscle surgery. Am J Ophthalmol 65:907–915

7.Swan KC (1954) Recession under Tenon’s capsule. AMA Arch Ophthalmol 51:32–41

8.Swan KC (1956) Resection under Tenon’s capsule. AMA Arch Ophthalmol 55:836–840

9.Velez G (1980) Radial incision for surgery of the horizontal rectus muscles. J Pediatr Ophthalmol Strabismus 17:106–107

10.Acuña O, Iturriaga H, Salgado C (2004) Estudio prospective y comparative de cirugía de estrabismo: abordeje limbo versus fórnix. Arch Chil Oftal 61:39–44

John Taylor is credited with the idea that strabismus could be treated by performing an operation to weaken the extraocular muscles [1]. In the mid eighteenth century he traveled throughout Europe and performed free tenotomies of the extraocular muscles. He often patched one eye and left town before the patch was removed and the results of the surgery became obvious. In 1839, Dieffenbach recorded the first case of an esotropia that was cured with a complete tenotomy of the medial rectus [1, 2]. Following his report, tenotomy of the medial rectus muscles became the standard method of treatment for patients with esotropia. As would now be expected, many patients developed large overcorrections. In an attempt to increase the predictability of strabismus surgery, Jameson introduced the scleral suture technique in 1922 [3]. He noted that direct suturing of the muscle to the sclera allowed the surgeon to more accurately grade the weakening effect as well as provided the surgeon with knowledge about the new attachment site on the globe. Modern-day conventional recessions are based upon Jameson’s original concept. Although the needles and sutures used for strabismus surgery have achieved significant advances since Jameson’s time, the basic recession technique used today remains remarkably similar. This chapter will review rectus muscle recession techniques including standard recessions, hang-back recessions, and other techniques designed to reduce the effect of rectus muscle contraction on the globe. In addition to general instructions about recession techniques, specific guidelines and suggestions for each of the four rectus muscles will also be addressed.

9.1General Principles for Recession of the Rectus Muscles

By moving a rectus muscle posterior to its original insertion site and reattaching it to the sclera, the length/tension curve of the muscle is changed. This has the effect of “weakening” the muscle’s effect on the globe. For most recessions, this effect is seen clinically only as a change in the alignment of the eye. Ductions do not appear to be limited unless a very large recession is performed, typically involving placement of the muscle posterior to the equator. This weakening effect probably occurs because of both a reduction in the distance between the origin and new insertion of the muscle, and changes in the relationship between Tenon’s capsule, the intermuscular septum, and

the rectus muscle pulleys. The relationship between the amount of recession required and the size of the deviation treated is not linear. As can be seen in Table 9.1, the recession effect obtained from retroplacing the medial rectus is initially linear, but as the size of the recession increases, the relative effect of the procedure increases. Once the muscle is placed behind the equator, the incremental effect of further recession is reduced.

The “safe” limit for a recession depends on the condition being treated. In the mid twentieth century, it was believed that the medial rectus muscle could not be recessed more than 5.0 mm without significantly interfering with movement of the eye. This belief resulted in many cases of congenital esotropia being undertreated. In an effort to improve the success rate of surgery, often three or four muscles were operated at one time. It was later recognized that recessions of at least 7 mm could be performed without producing an adduction deficit. This led to a higher success rate of surgery, particularly for larger deviations, while avoiding the need to operate on a third or fourth muscle. Some studies have shown that even larger recessions can be performed on the medial rectus muscle without creating a duction deficit [4]. In some situations, a rectus muscle may be recessed considerably further. With the use of the hang-back recession technique, large recessions can be performed easily and safely. The intentional creation of a duction limitation may be required for effective treatment of some conditions. For example, a patient with a large exotropia in a poorly seeing eye will usually gladly tolerate the requisite abduction deficit that will occur after a large recess and resect operation in order to avoid the need to operate on the sound eye. Therefore, we do not subscribe to the notion of a “maximum” rectus muscle recession.

Table 9.1. Typical size of bilateral medial rectus recession for esotropia

9.2 Measurement of Recession

9.2.1 Muscle Insertion Artifacts

The distance a muscle is moved during a recession procedure can be measured from either its original insertion site or its distance from the limbus. There are a number of reports in the literature demonstrating variability of rectus muscle insertion sites as referenced to the limbus [5, 6]. This is especially true of the medial rectus muscle insertion. The relationship between the muscle insertion site and the limbus has been shown to be particularly variable in young patients before the anterior segment is fully developed. Sevel [7] examined the insertions of the extraocular muscles and discovered that posterior movement of the muscle tendon from the limbus along with growth of the anterior segment of the eye cause the rectus muscle insertions to reach their approximate adult location sometime between the ages of 18 months and 2 years. This fact has also been demonstrated clinically. Barsoum-Homsy [8] measured the distance between the medial rectus muscle insertion site and the limbus in children under 1 year of age undergoing surgery for congenital esotropia. Among the 52 eyes examined, the insertion site varied between 3.0 and 5.5 mm posterior to the limbus.

In addition to the variability of rectus muscle insertion distances from the limbus, other authors have reported potential intraoperative changes in the apparent insertion site, which can affect the recession measurement. Keech and coworkers [9] found that disinsertion of the medial rectus muscle resulted in a mean reduction in the distance between the muscle insertion site and the limbus of 0.9 mm. In addition to this change, the use of fixation forceps on the insertion, to abduct the eye, resulted in an advancement of the medial rectus muscle insertion an additional 0.3 mm toward the limbus. Kushner and co-workers [10] demonstrated a similar anterior displacement of rectus muscle insertion sites of approximately 1 mm when the globe was fixated by placing forceps on the rectus muscle stump after detachment of the muscle from the sclera. Because of the potential for the insertion site to vary between individuals and for the insertion site to change during the course of surgery, some surgeons are concerned that measuring the amount of recession from the original muscle insertion site may alter the amount of recession actually achieved from a given surgery. Surgeons with this belief recommend measuring the desired amount of retroplacement of the muscle from the limbus, because the limbus represents a stable landmark from which to base this important surgical measurement [11].

The axial length of the globe has also been reported to play an important role in the size of a rectus muscle recession required for a given deviation [12]. Some surgeons alter their surgical plan based upon the axial length of the eye [12, 13].

The distance the muscle is moved along the globe can be measured using a cord length or arc measurement. Clark and Rosenbaum [14] performed a geometric analysis to determine the measurement difference between true arc length measurements compared with ruler and caliper measurements based upon the size of the recession being performed and the axial

Chapter 9

length of the eye. They found that both a curved ruler and caliper were accurate when measuring arc lengths of 9.0 mm or less. For longer arc length measurements, accuracy was found to be dependent upon the axial length. For recessions greater than 9.0 mm in magnitude, a curved ruler was more accurate than calipers when the axial length of the eye was typical for the average patient population (21–24 mm). However, for smaller and larger eyes, a curved ruler can introduce clinically important measurement errors for arc length measurements as small as 12 mm in small eyes and 14 mm in large eyes. We generally use a caliper for our measurements. For larger recessions where the use of a caliper can be cumbersome, the measurements can be made in two steps. The amount of recession to be performed is divided in half. The caliper is then used to mark the sclera for one-half the recession distance. This mark is then used to perform a second measurement of equal magnitude to mark the final position for suture placement.

9.3Specific Considerations for Surgery on Individual Rectus Muscles

Unique considerations for performing surgery on each of the rectus muscles will be reviewed, followed by a review of rectus muscle recession techniques.

9.3.1 Medial Rectus Muscle

Unlike the other rectus muscles, the medial rectus muscle does not have any direct attachments to an adjacent oblique muscle. Because of this, the medial rectus muscle is more difficult to retrieve should it be lost at the time of surgery. Excessive dissection of the intermuscular membrane and muscle capsule is discouraged, in part for this reason. In addition to being unnecessary, it may alter the muscle pulleys and increase the risk of inadvertent muscle damage during surgery [15].

9.3.2 Inferior Rectus Muscle

The inferior rectus muscle has fascial attachments to Lockwood’s ligament, the inferior orbital septum, and the tarsus of the lower eyelid. Because of these attachments, recession of the inferior rectus may produce retraction of the lower eyelid (Chap. 26). Lid retraction may be seen with even moderate inferior rectus muscle recessions. Therefore, techniques designed to minimize the risk of lid retraction when performing a recession on an inferior rectus muscle are recommended, especially when large recessions are performed. Briefly described here, these techniques are reviewed in detail in Chap. 26. Meyer and co-workers [16] described the use of primary infratarsal lower eyelid retractor lysis to prevent eyelid retraction after inferior rectus muscle recession [16]. This technique prevented lower eyelid retraction even with recessions of up to 10 mm. Advancement of the capsulopalpebral head after recession of

the inferior rectus muscle has also been shown to minimize lower eyelid retraction [17]. Finally, generous dissection of the attachments between the inferior rectus and the lower eyelid can reduce lower eyelid retraction (>Fig. 9.1). Dissection is required to at least 12 mm posterior to the insertion of the inferior rectus. It is important to visualize the adjacent vortex veins during this dissection to avoid injuring them, a complication that can cause significant bleeding.

9.3.3 Lateral Rectus Muscle

The insertion site of the inferior oblique muscle lies posterior to that of the lateral rectus muscle insertion. Therefore, the strabismus surgeon should exercise caution when attempting to isolate the lateral rectus muscle insertion on a muscle hook to avoid inadvertently incorporating the inferior oblique muscle on the muscle hook. This risk can be minimized by either passing the muscle from the superior aspect of the lateral rectus muscle insertion or by avoiding the tendency to pass the hook too deeply into the orbit during attempts to hook the lateral rectus muscle. During reoperation procedures on a previously

Fig. 9.1. Recession of the inferior rectus muscle demonstrating the appearance of the muscle after generous dissection of the attachments between the inferior rectus muscle and the lower eyelid retractors to minimize lower eyelid retraction following inferior rectus recession

recessed lateral rectus muscle, this may be more difficult. Direct visualization of both the lateral rectus and the inferior oblique muscles is helpful. If the insertion of the inferior oblique muscle is mistakenly moved during surgery on the lateral rectus muscle, unexpected motility disturbances may occur (Chap. 25).

9.3.4 Superior Rectus Muscle

The superior oblique tendon passes inferior to the superior rectus muscle starting approximately 5 mm posterior to the nasal border of the superior rectus muscle insertion. It is important to avoid inadvertently hooking the superior oblique tendon when the superior rectus muscle is initially hooked. If the superior oblique tendon is unknowingly hooked along with the superior rectus muscle insertion, it is possible to perform an unintentional tenotomy on the superior oblique tendon when the superior rectus muscle is detached from the globe, potentially producing a significant iatrogenic motility disturbance. Once the insertion of the superior rectus muscle is isolated on a muscle hook, it should be inspected to ensure that the superior oblique tendon has not been inadvertently hooked. If this has occurred, the superior oblique tendon can be gently lifted off the surface of the globe while a new muscle hook is placed under the superior rectus muscle insertion, excluding the superior oblique tendon (>Fig. 9.2). The superior oblique tendon can also be retracted posteriorly, away from the superior rectus muscle insertion, while a new hook is placed.

Similar to the relationship between the inferior rectus muscle and the lower eyelid retractors, the superior rectus muscle has significant attachments to the levator muscle of the upper eyelid through the fascial sheaths of these two muscles. Moderate to large recessions of the superior rectus may produce upper eyelid retraction. Dissecting these attachments at least 12 mm posterior to the insertion site of the muscle at the time of superior rectus muscle recession will help to minimize this postoperative complication (Chap. 26).

9.4 Rectus Muscle Recession Techniques

The general technique for rectus muscle recession is similar for each of the four rectus muscles. Specific concerns regarding each individual rectus muscle are reviewed above. Each of the rectus muscles may be exposed using either a limbal or a fornix incision. In most situations, the choice of surgical approach depends entirely on the preference of the surgeon. There are a few isolated situations in which one surgical approach may be preferred over the other as reviewed in Chap. 8. For most cases, we prefer a fornix incision. Reoperations and surgery on patients with a thin or friable conjunctiva are are often preferentially operated through a limbal incision, a technique that requires minimal stretching of the conjunctiva, reducing the risk of its tearing, a complication which may make subsequent closure more difficult. The detailed techniques of conjunctival incisions, rectus muscle isolation, and of conjunctival closure are reviewed in Chap. 8, and will not be repeated here.

Fig. 9.2a,b. Isolation of the superior rectus. a The tendon of the superior oblique has been unintentionally isolated in the hook along with the superior rectus muscle. b The superior rectus muscle and superior

9.4.1Standard Rectus Muscle Recession Technique

9.4.1.1Placing Suture Near the Muscle Insertion

After the rectus muscle is isolated on a muscle hook, a suture is placed in the muscle near its insertion into the sclera. The suture should generally be placed no closer than 1 mm from the muscle’s insertion into the sclera. We prefer the use of a single double-armed polyglactin suture. A suture pass is started at the midpoint of the muscle and placed half thickness through the muscle. This is referred to as the transverse pass. The needle is allowed to exit at the border of the muscle (>Fig. 9.3a). When passing the needle away from the surgeon, it is sometimes difficult to visualize the exit location of the needle from the muscle. If the needle stays in place once its tip has exited the muscle, it is in proper location. However, if the needle appears unstable, it has most likely been passed full thickness through the muscle (>Fig. 9.3b). In this case, the suture should be partially withdrawn and passed again. The suture is then passed in the opposite direction starting in the center of the muscle, so that the transverse pass crosses the entire width of the muscle posterior to its insertion site. The small distance between the sclera and the suture adds a negligible resection effect following surgery.

Following completion of the transverse pass, locking suture passes are made at the borders of the muscle near the insertion.

oblique tendon are lifted off the surface of the globe to allow passage of a second muscle hook to isolate the insertion of the superior rectus muscle only

These border locking suture passes should incorporate at least 1mm of muscle to achieve a secure muscle-suture union (Unpublished data). The needle is passed full thickness through the muscle from the posterior to the anterior aspect of the muscle and behind the transverse suture pass (>Fig. 9.4a). The needle should not be passed through the anterior ciliary vessels, as this may result in significant bleeding. It is sometimes helpful to pass the needle around these vessels in order to ligate them and prevent bleeding when the muscle is later detached from the globe. Care should be taken to pass the needle directly through the muscle. After the suture is passed full thickness through the muscle, the needle holder is passed through the suture loop, grasping the needle and pulling it through the suture loop to create a locking bite (>Fig. 9.4b). It is preferable to grasp the suture rather than the needle during this step to prevent damage to the needle.

9.4.1.2Detachment of the Muscle from the Globe

The muscle sutures are placed between the index finger and thumb of the hand holding the muscle hook. Independent control of the sutures is helpful. If the surgeon grasps the muscle hook in his or her hand and is able to pull the sutures with his or her fingers independently of the hook, more space can be created between the insertion site of the muscle and the sutures, facilitating detachment of the muscle and reducing the risk of cutting the muscle sutures (>Fig. 9.5).

Fig. 9.3a,b. Transverse needle pass near the muscle insertion. a The needle is placed into the muscle near the midpoint of the muscle width near the insertion site. It is passed half thickness through the muscle

until the needle tip exits the border of the muscle. b Note that the tip of the needle tends to fall toward the globe if the needle has been unintentionally passed full thickness through the muscle

Fig. 9.5. Independent control of the muscle hook and the sutures while detaching the muscle from the sclera. Note that the surgeon is able to independently lift the sutures and provide more space to safely cut the muscle from its insertion site

9.4.1.3Securing the Muscle to the Sclera at its New Location

Locking forceps are placed on the edges of the muscle stump after the muscle has been detached from the sclera. The sclera is marked to identify the entrance site for the upcoming needle pass where the new insertion site of the muscle will be

placed. This measurement can be made from the limbus or the original insertion site of the muscle as described previously (>Fig. 9.6a, b). The mark on the sclera is made by indenting the sclera at the desired recession site using a caliper. This maneuver displaces fluid from the sclera and allows visualization of the underlying choroid, creating the appearance of a blue spot on the sclera. The surgeon should be careful not to press too firmly with the caliper at either the anterior or the posterior site of the caliper placement. Inexperienced surgeons often neglect to carefully observe the anterior tip of the caliper while pressing on the sclera with the posterior caliper tip. They may unknowingly place too much pressure on the anterior tip of the caliper and perforate the globe during this step. The sclera may be marked for both needle passes at this point, if desired. However, the second mark often disappears by the time the surgeon is ready to pass the second needle. The caliper tips can be covered with ink from a sterile gentian violet skin-marking pen to create a sustained mark on the sclera, if desired.

The needle is then placed into the sclera at the previously marked positions. The needle pass in the sclera should be a minimum of 2 mm in length and 200 µm in depth [11]. Many surgeons prefer much longer scleral bites, but these minimum values are sufficient to secure the muscle to the sclera. The first needle exits the sclera and is allowed to remain in place. The second needle is then passed in a similar fashion. This “crossed swords” technique allows the sutures to be passed in close proximity to each other without the second needle pass damaging the previously passed suture (>Fig. 9.7). It is not necessary however, for the two needles to exit the sclera in close proximity. The sutures are then pulled through the sclera in the direction of their pass in order to avoid cheese wiring of the sclera.

The sutures are then tied and cut making certain that the muscle remains in place at its new insertion site by maintaining anterior traction on the sutures while they are being tied (>Fig. 9.8). If the needle passes are made too close to each other, the central portion of the muscle may sag posteriorly. This can be corrected by passing the needle back through the midportion of the muscle and behind the original suture, prior to cutting the muscle sutures. The suture is then tied to bring the central portion of the muscle up to its intended attachment site (>Fig. 9.9).

9.4.2 Hang-Back Recession Techniques

9.4.2.1 Introduction

In an attempt to improve outcomes associated with conventional extraocular muscle surgery, Jampolsky popularized the concept of the adjustable suture in the 1970s [18]. Use of adjustable sutures led to the development of hang-back or suspension recession procedures. Repka and Guyton [19] performed strabismus surgery using techniques that are key to the adjustable suture technique, but without attempting to perform a postoperative adjustment. This procedure became known as a hang-back recession. The procedure described by