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

the limbus and has its base in the fornix. The advantages and disadvantages of each of these two primary strabismus surgery incision approaches are reviewed. An earlier approach introduced by Swan [7, 8] relied on an incision through the conjunctiva that was concentric with the corneal limbus and located over the rectus muscle to be operated. The Swan incision is reviewed primarily for historical interest, as it has largely been abandoned due its difficulty and higher rate of complications. Other surgical approaches have been proposed, but have never gained wide acceptance. Velez [9], for example, described a radial incision for surgery on the horizontal rectus muscles.

Any surgical approach for strabismus surgery must provide adequate surgical exposure, be associated with minimal postoperative adhesion and scar formation, be easy to create and to close, and should facilitate reoperation by limiting the amount of scarring that occurs postoperatively in the episcleral space. The choice of surgical incision is primarily based on surgeon preference, though some situations are best managed with one surgical approach preferentially. For example, while reoperations can usually be easily performed through either a fornix or limbal incision, complex reoperations involving exploration of the posterior aspect of the orbit and involving extensive scarring are often more easily carried out through a limbal incision. Posterior fixation sutures, especially when performed more than 12 mm posterior to the limbus, can often be performed more easily (and perhaps more safely) through a limbal incision, though use of a fornix incision is reasonable in most situations requiring a posterior fixation suture.

The inferior oblique muscle is almost always approached surgically through a fornix incision. If the inferior rectus muscle or the lateral rectus muscle is to be operated simultaneously, inferior oblique muscle surgery can be performed through the same limbal incision created to gain access to these rectus muscles. The superior oblique tendon is usually, but not always, operated through a fornix incision. Because identification and isolation of the superior oblique tendon can sometimes be difficult, it is not unreasonable to approach the superior oblique tendon through a limbal incision or to convert a fornix incision to a limbal incision to improve surgical exposure, if necessary.

8.2.1 Fornix (Cul-de-Sac) Incision

The fornix conjunctival incision approach to strabismus surgery was popularized by Parks [6] and has undergone modifications by several surgeons. The name is misleading because the incision is not actually made in the fornix, but rather is made on the bulbar conjunctiva, like all conjunctival incisions for strabismus surgery. Fornix incisions have several key advantages compared to limbal incisions. Fornix incisions are easier to construct, require less time than limbal incisions, and they are easier to close at the end of the case. Three muscles can be accessed through a single fornix incision in any quadrant, including the two adjacent rectus muscles and one oblique muscle. The oblique muscles, however, are rarely accessed through an

inferonasal fornix incision. Fornix incisions are more difficult to use when the conjunctiva is extremely thin, such as in very elderly patients, but can be used for surgery on a patient of any age. We routinely use a fornix incision for strabismus surgery on patients older than 60 years of age. A fornix incision is not a good option for surgery performed under topical anesthesia (Chap. 6), because the manipulation required to perform surgery through a fornix incision is usually not well tolerated by the patient when using the topical anesthesia approach.

Patients tend to be more comfortable postoperatively following a fornix incision compared to those who have had surgery through a limbal incision [10] and the cosmetic appearance of the eye is usually superior in the immediate postoperative period. Closure is straightforward and complications related to closure are less likely to occur with fornix incisions compared to limbal incisions (Chap. 19). Additionally, reoperation of a muscle that was initially approached through a fornix incision is typically easier than for one that was initially approached through a limbal incision because there tends to be fewer adhesions between the conjunctiva and episclera anterior to the muscle insertion when a fornix incision has been used.

A disadvantage of the fornix approach is the fact that exposure of the surgical site is not as generous as that obtained through a well-constructed limbal incision. This is most likely to be a problem with procedures that require surgical manipulation 12 mm or more posterior to the limbus such as very large recessions, posterior fixation sutures, and reoperations involving the posterior orbit. The option of conjunctival recession is not possible with a standard fornix incision. Additionally, the technique is more difficult to learn in many ways than is the limbal approach, and until the surgeon is experienced in performing surgery through a fornix incision, a relatively skilled assistant is essential.

8.2.1.1 Fornix Incision Technique

A fornix conjunctival incision can be made in any of the oblique quadrants between adjacent rectus muscles. In general, incisions placed in the lower quadrants are preferred to those placed in the upper quadrants (>Fig. 8.9). The incision is generally made parallel or nearly parallel to the lid margins, beginning approximately 8 mm posterior to the limbus and extending nasally or temporally as needed. Some surgeons prefer fornix incisions that are more obliquely oriented. This choice is a matter of surgeon preference and has no significant impact on the outcome of surgery or healing. The precise location of a fornix incision depends on a number of factors, including which muscle(s) is to be operated, surgeon preference, the type of surgery (recession versus resection), the size of the recession, the presence of other ocular pathology, and previous surgery. For example, the incision is often placed more posteriorly and closer to the muscle if a large recession is planned, because an incision placed in this manner allows greater exposure of a surgical site that is located further from the corneal limbus.

Fig. 8.9. Potential locations for placement of a fornix incision for rectus muscle surgery. Incisions placed in the lower quadrants are preferred, when possible

8.2.1.1.1 Initial Incision

The globe is grasped 1–2 mm posterior to the corneal limbus and positioned for surgery. Curved, locking 0.5-mm forceps are excellent for this maneuver. The conjunctiva is grasped with a fine-tipped forceps, placed under mild anterior traction, and an incision 8–10 mm in size is made (>Fig. 8.10a). Alternatively, blunt-tipped scissors can be placed directly on the conjunctiva and the incision made without grasping the conjunctiva with forceps (>Fig. 8.10b). Moderate pressure needs to be maintained on the scissors during this maneuver. When making a fornix incision medially, the incision should not be continued into the plica semilunaris as this will result in a visible notch in the plica semilunaris postoperatively. Tenon’s fascia is then grasped with forceps and incised to gain access to the episcleral space (>Fig. 8.10c). Some surgeons recommend orienting the incision through Tenon’s capsule at a right angle to the conjunctival incision. This orientation probably offers no significant clinical advantage because traction on the incision during surgery significantly distorts the initial opening, and incision through Tenon’s capsule is more difficult to perform in this manner. It is rarely possible to distinguish a difference in orientation between the conjunctival and Tenon’s capsule incisions at the end of surgery, before closure of the conjunctiva is done. Some surgeons remove a small piece of Tenon’s capsule to facilitate access to the episcleral space.

Fig. 8.10a–c. Initiation of a fornix incision using one of two approaches. a Placing the adjacent conjunctiva under traction followed by incision, or b direct incision with blunt-tipped scissors without traction

on the conjunctiva. c Tenon’s fascia is then incised to gain access to the episcleral space

8.2.1.1.2 Isolation of a Rectus Muscle

A small hook is used to initially isolate the rectus muscle insertion. A Stevens hook is ideal for this purpose. The hook is passed through the incision into the episcleral space. The toe of the hook should initially be placed in contact with the sclera. The hook is then advanced toward the rectus muscle. As the hook makes contact with the muscle, it is rotated so that it becomes parallel with the muscle insertion (>Fig. 8.11a). Placing the toe of the hook initially in contact with the sclera helps

to assure that the hook is directed under the muscle, rather than in some other, unwanted plane. The small hook is then replaced by a hook that is slightly larger than the width of the muscle insertion (>Fig. 8.11b). A Jamison hook or Green hook is often used for this purpose. To help ensure that the entire width of the muscle insertion has been isolated on the hook, a second large hook is often passed, replacing the existing hook. The assistant surgeon can be very helpful during these steps by retracting the incision with a small hook to ensure that the surgeon has constant access to bare sclera upon which to initiate passage of the muscle hooks.

Fig. 8.11a,b. Isolation of a rectus muscle insertion. a A small hook is used to initially isolate the muscle insertion through the episcleral space. The toe of a hook, initially in contact with the sclera, is rotated parallel to the muscle insertion as the hook is advanced toward the rectus muscle. b The small hook is then replaced by a larger hook to engage the entire muscle insertion

8.2.1.1.3 Heel or Toe Maneuver

Before the conjunctiva is retracted to expose the muscle insertion, the heel or toe maneuver can be carried out to help ensure that the entire muscle insertion has been isolated on the hook (>Fig. 8.12). The toe of the hook is the distal tip of the hook, which often terminates in a bulb or other protrusion. The heel of the hook represents the right angle bend in the distal portion of the hook. After hooking the rectus muscle, the toe of the hook is angled upward, tenting the conjunctiva. An attempt is then made to gently rotate the toe of the muscle hook toward the limbus. If the toe of the muscle hook easily advances to the limbus, the entire muscle insertion has probably been isolated. On other hand, if the toe fails to advance to the limbus, but instead the heel of the hook tends to move posteriorly, the surgeon has failed to isolate the entire muscle insertion and another hook should be passed. Rarely, the surgeon may split the rectus muscle during this maneuver and may be fooled into believing that the entire muscle has been isolated. The pole test, described below, will allow later detection of this problem.

8.2.1.1.4 Exposure of the Muscle Insertion

A small hook, such as a Jamison hook, is then is placed between the conjunctiva and the muscle insertion anteriorly. This hook it used to slowly retract the conjunctiva over the muscle insertion while simultaneously rotating the muscle insertion into the incision using the large hook that is under the muscle insertion (>Fig. 8.13a). Once the conjunctiva has been retracted, the intermuscular septum can be seen extending from the toe of the hook toward the globe. The intermuscular septum is grasped with a pair of toothed forceps. A pair of blunt-tipped scissors is used to incise the intramuscular membrane to ex-

Chapter 8

pose the toe of the muscle hook and underlying bare sclera (>Fig. 8.13b). Tenon’s fascia is lightly grasped 2–3 mm anterior to the muscle insertion and placed under mild traction. It is incised down to bare sclera approximately 1 mm anterior to the muscle insertion (>Fig. 8.13c). Cutting too close to the muscle insertion during this step can result in bleeding from the anterior ciliary vessels and/or damage to the muscle. Some surgeons prefer to omit this step.

8.2.1.1.5 The Pole Test

A maneuver referred to by some as the pole test is recommended at this stage of the operation or prior to dissection of Tenon’s capsule anterior to the muscle insertion, as a final step to ensure that the entire rectus muscle insertion has been isolated on the muscle hook (>Fig. 8.14a). The toe of a small hook, such as a Stevens hook, is placed on bare sclera located behind the muscle insertion. While maintaining mild pressure on the globe, the hook is slowly moved around the muscle insertion until it is located anterior to the insertion. If the muscle has been split during attempts to isolate the muscle and thus has not been fully isolated on the large muscle hook, the small hook cannot be advanced anterior to the muscle insertion, instead becoming trapped by the portion of the muscle insertion that has not been isolated (>Fig. 8.14b). When this occurs, the surgeon is obligated to identify and isolate the remainder of the muscle on the hook before proceeding with surgery.

8.2.1.1.6 Dissection of the Muscle Fascia

Next, the proximal end of the large muscle hook is directed toward the limbus and the rectus muscle is maintained under mild traction. The intermuscular septum is dissected with

Fig. 8.12. The heel or toe test to ensure that the entire muscle insertion has been isolated. The toe of the hook is angled in an anterior direction, tenting the conjunctiva, and then is rotated toward the limbus. On the right: advancement of the toe to the limbus suggests that the

entire muscle insertion has been isolated while (left) failure to advance to the limbus indicates that the entire insertion has not been isolated. The dotted line represents the position of the insertion.

Fig. 8.13a–c. Exposure of a rectus muscle insertion. a A small hook is used to slowly retract the conjunctiva over the muscle insertion while simultaneously rotating the muscle insertion into the incision. b The

sharp dissection to expose the border of the rectus muscle (>Fig. 8.15a). If the surgeon prefers to dissect the epimuscular fascia, it is lightly grasped with forceps, placed under traction, and incised just above the plane of the muscle belly (>Fig. 8.15b). The decision on how extensively to dissect the intramuscular septum and muscle capsule is, to a large extent,

intermuscular septum is grasped with a pair of toothed forceps and incised, exposing underlying bare sclera. c Tenon’s fascia is incised down to bare sclera approximately 1 mm anterior to the muscle insertion

dependent on surgeon preference and the type of surgery to be performed. Some surgeons perform minimal dissection of these structures, while others routinely perform large dissections. Recession, resection, tucking, and other procedures can then be performed on the now isolated rectus muscle as described in later chapters in this textbook.

8.2.1.1.7 Closure of a Fornix Incision

The decision to perform suture closure of a fornix incision depends on surgeon preference, the state of the patient’s conjunctiva at the end of the case, and the appearance of the incision following surgery. The anterior aspect of the incision is gently pushed posteriorly (>Fig. 8.16a). If the edges of the incision are well approximated by this maneuver, suture closure may be omitted (>Fig. 8.16b). Suture closure is recommended if close approximation of the incision edges does not occur with this maneuver and when the incision is particularly large (>Fig. 8.16c). Suture closure is almost always recommended when a fornix incision has been used to perform surgery on the thin conjunctiva of an elderly patient, because close reapproximation of the wound edges in this setting is uncommon. If suture closure is warranted or desired, one or two simple interrupted sutures at intervals along the incision or a running suture closure may be utilized. Buried knots may be associated with less ocular discomfort postoperatively.

8.2.2 Limbal Incision

The limbal approach to strabismus surgery was popularized by von Noorden [5]. Many surgeons prefer limbal incisions because they are universally applicable to any and all rectus muscle operations. The advantages of limbal incisions are many,

including excellent exposure. Limbal incisions may be especially helpful when performing surgical maneuvers more than 12–13 mm posteriorly to the limbus. The surgeon is usually less dependent on a skilled surgical assistant when using a limbal approach. Reoperations, especially complex reoperations, are thought by many surgeons to be more easily performed through a limbal incision, though a fornix approach can be used by the experienced surgeon for all but the most unusual reoperation procedures. Only one rectus muscle can be operated on through a standard limbal conjunctival incision.

The disadvantages of limbal incisions are also numerous. Closure of a limbal incision is more difficult and time consuming than closure of a fornix incision and requires careful attention to detail. If the edges of the conjunctiva are not correctly identified, a number of potential complications can occur, including coiling and retraction of the conjunctival flap and anterior advancement of the plica semilunaris, both of which can be very distressing to patients (Chap. 19). The novice surgeon is often well served to mark the intended position of the limbal incision prior to making it, using a sterile gentian violet skin-marking pen (>Fig. 8.17). This technique not only aids in accurate construction of a limbal incision, but also helps to ensure accurate closure because the dye is usually still visible on the conjunctival edges at the end of surgery, facilitating identification of the corners of the conjunctival flap. This dye is readily washed away during surgery and postoperatively and we have never seen permanent conjunctival pigmentation as a result of its use when used to teach residents the techniques of limbal incision construction.

Fig. 8.17. A sterile gentian violet skin-marking pen can be used to mark the position of the limbal incision aiding both in the construction of the incision and its closure

The cosmetic appearance of a well-performed and optimally healed limbal incision is generally excellent, and equal to that of a fornix incision. Frequently, however, conjunctival ridges and bumps can be seen on the conjunctival surface even years after surgery. In the immediate postoperative period, eyes that have undergone surgery through a limbal incision tend to be less comfortable than those that have undergone a fornix incision [10].

The limbal approach to strabismus surgery involves creation of a conjunctival flap that is initiated at the limbus and has its base in the fornix. The incision typically involves a region corresponding to 2 to 3 o’clock of the conjunctiva adjacent to

the corneal limbus, with radial incisions that are 8–10 mm in length into adjacent oblique conjunctival quadrants between adjacent rectus muscles. Placement of limbal incisions for surgery on each of the rectus muscles is shown in Fig. 8.18. Several techniques have been described for the creation of a limbal incision. Any of these techniques is reasonable provided that it results in the construction of a limbal incision that is smooth, has right angle turns connecting the limbal and radial components, and provides adequate exposure of the surgical site. One of the simplest techniques is described below.

8.2.2.1 Limbal Incision Technique

8.2.2.1.1 Initial Incision

The surgeon may be seated on the side of the globe opposite the rectus muscle to be operated on, or seated to the right for surgery on the superior rectus muscle. After retracting the globe to expose the conjunctiva over the muscle to be operated, the conjunctiva along the path of one planned radial incision is grasped 2–3 mm posterior to the corneal limbus and incised (>Fig. 8.19a). This should produce an incision that starts at the corneal limbus and extends 4–6 mm posteriorly. One blade of a pair of blunt-tipped scissors is then directed posteriorly and the radial incision extended. The conjunctiva is then elevated and the limbal component of the incision created, often preceded by blunt dissection of the episcleral space near the corneal limbus. A second radial incision is then made at a right angle to the limbus (>Fig. 8.19b). A common mistake that is made when creating the second radial component of the incision involves vertical orientation of the scissors, which produces a conjunctival dog-ear flap (>Fig. 8.19c), rather than an abrupt transition from the limbal to the radial component of the incision, making closure more difficult. Instead, the scissors should be oriented horizontally and flush against the sclera, which produces a sharp, right angle turn.

the borders of the muscle to incise the intermuscular septum (>Fig. 8.20c). The amount of dissection of these structures depends on the preference of the surgeon and the procedure being performed. Less dissection is usually done for recession procedures than for resection procedures. Some surgeons prefer utilizing a cotton tip applicator or a muscle hook (Chap. 9) to manually disrupt the fine adhesions of the muscle capsule to the muscle belly and the attachments of the intermuscular septum to the borders of the muscle. Recession, resection, tucking, and other procedures can then be performed on the now isolated rectus muscle as described in later chapters in this textbook.

8.2.2.1.3 Closure of a Limbal Incision

After completion of surgery on the muscle, careful closure of a limbal conjunctival incision is required and is particularly im-

Fig. 8.19a–c. Creating a limbal incision. a An initial radial component of the incision is created, b followed by the limbal and a second radial component of the incision. The scissors should be oriented horizontally and flush against the sclera as the radial portion of the incision is created. c Failing to do so can produce a conjunctival dog-ear flap (arrowhead) instead of the desired sharp, right angle incision (arrow)

portant following surgery on the medial rectus muscle where improper closure can have particularly significant adverse functional and cosmetic implications (Chap. 19). The conjunctiva should be unrolled with forceps and the anterior corners of the conjunctival flap identified and grasped with forceps. The surgeon should not assume that the anterior corners of the incision have been identified using this technique alone. The underlying adherent Tenon’s fascia should be lightly grasped with forceps and pulled gently toward the limbus. This maneuver often results in further unfolding of the conjunctival flap, allowing the surgeon to identify the true corners of the flap (>Fig. 8.21a). A suture is then passed through each edge of the conjunctival flap and the edges of the flap sutured to the conjunctiva adjacent to the limbus (>Fig. 8.21b). Buried or exposed knots can be used to close the incision based on surgeon preference, though buried knots may be associated with improved postoperative patient comfort.

A modification of the limbal incision that can be used for most simple rectus muscle operations involves creation of a single radical incision (>Fig. 8.22). The left radial incision is generally omitted for a right-handed surgeon and the right radial incision omitted for a left-handed surgeon. Upon completion of surgery, closure requires placement of a single suture.

Following long-standing strabismus, the conjunctiva can become contracted, producing restrictive forces on the globe that must be reduced or eliminated in order to correct the ocular deviation. One advantage of a limbal incision is that the conjunctiva can be easily recessed when warranted. A simple method of conjunctival recession involves placement of sutures