Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology Current Thought and A Practical Guide_Wilson, Saunders, Trivedi_2008

Contents

16.3Patient Selection  . . . . . . . . . . .   214

16.4.2Patient Comfort, Alertness, and Cooperation

for Postoperative Motility Assessment  . .   215

16.4.3Sedation Protocol for Suture Adjustment  .   216

16.5Surgical Technique  . . . . . . . . . .   217

16.5.1 Limbal vs FornixApproach  . . . . . .   217

16.5.2Technique  . . . . . . . . . . . . .   217

16.5.5Adjustable Superior Oblique Suture Spacer    218

16.7Complications  . . . . . . . . . . . . . . . . . . . . . . .   219

Core Messages

•Adjustable sutures provide a second chance to improve the outcome of first surgery.

•Adjustable sutures may reduce the need for reoperations but add to the time and complexity of surgery.

•Ideal candidates are patients in whom the standard strabismus dosages may not apply.

•Adjustable sutures make intellectual sense, but solid data of the advantage are lacking.

16.1 Introduction

Strabismus surgery is by no means an exact science.

The outcome of surgery depends partly on measurements, partly on the experience and intuition of the surgeon, and very much on the healing capacity and fusion status of the patient. The goal of surgery is to align the eyes with fewest procedures; however, the surgeon may encounter surprises when the patient recovers from surgery. The same amount of surgery for the same angle of deviation will yield different results in different patients, often for no obvious reason. This is especially true for long-standing complicated strabismus, reoperations, innervational abnor-

malities, restrictive myopathies, or following injuries to the eye.

A search for improved accuracy in strabismus surgery led to an approach which allowed adjustment during the early postoperative period. Adjustable suture strabismus surgery was first described by Claude Worth in 1908 [8]; however, the first modern account of adjustable suture surgery was presented by Jampolsky in 1975 [13, 14]. He described a two-stage adjustable suture technique with surgery under general anesthesia and adjustment of the ocular position under local anesthesia on the morning after surgery or on the same day after 4−8 h, when the patient was fully alert.

The basic principle of the adjustable suture technique is to secure the extraocular muscle to the sclera using a temporary or sliding knot. After the patient has recovered from anesthesia, the alignment of the eyes is checked. The length of suture between the attachment site and muscle may be shortened or lengthened to fine-tune the alignment in an awake patient.

The adjustments are usually performed within 24 h of the primary surgery. The goal of this extra step is to decrease the need for reoperation.

A number of surgeons have used adjustable sutures in adults to improve immediate postoperative alignment. They have described their experiences with adjustable sutures [3, 17, 22, 26, 30, 31, 32,], but there havebeennoprospectiverandomizedcontrolledtrials that directly compare non-adjustable with adjustable sutures for strabismus surgery in adults [29]. There are very few reports on the use of adjustable suture surgery in children [5, 6, 10, 27]. This is most likely because of the difficulty obtaining the cooperation of a child for postsurgical manipulations.

In this chapter, we describe current approaches to adjustable suture surgery, with an emphasis on our preferred techniques.

16.2 Indications

The ideal candidates for adjustable suture strabismus surgery are patients in whom the standard strabismus surgical dosages may not apply (Table 16.1). Patients with combined horizontal, vertical, and torsional deviationsarealsothoughttobenefitfromtheadjustable suture technique. Adjustable sutures are particularly useful when the aim of surgery is to regain binocular

Table 16.1  Standard indications for adjustable suture strabismus surgery

Restrictive strabismus (thyroid ophthalmopathy, scleral buckle, or anesthetic myotoxicity)

Previous trauma or surgery Slipped, lost, or disinserted muscles

Incomitant deviations (Duane syndrome, myasthenia gravis, or paralytic strabismus)

Any long-standing complex strabismus

single vision and when the patient has a risk of postoperative diplopia. In these cases the ability to adjust after surgery provides reassurance to the patient.

It is our practice to use adjustable sutures on all muscles of all adults, even those with comitant strabismus and no prior surgery. We also use adjustable sutures in selected children who meet the standard indications mentioned in Table 16.1.

16.3 Patient Selection

The adjustment procedure can cause some discomfort and can evoke substantial anxiety in patients; therefore, patient selection is crucial if the suture adjustment is to be performed without sedation. Most surgeons recommend the technique in children older than 12 years; however, we have found that it can be performed in cooperative children as young as 5 years. Dawson and co-authors found that the supervised, active participation of a parent or caretaker was a key feature in the success of completing the adjustment [5].

Many surgeons perform the “Q-tip” test to identify patients who will be suitable for the adjustment procedure. This test consists of touching a cotton swab or twirled tissue end to the medial and/or lateral aspect of the unanesthetized bulbar conjunctiva. If the patient is able to tolerate manipulation of the bulbar conjunctiva, then he or she should do well with the adjustment procedure. If the patient fails the Q-tip test, then it may be best to either perform non-adjust- able surgery or to arrange for backup sedation.

In young children, the use of the adjustable suture technique may require two stages of anesthesia. The surgery is carried out, the child is assessed when fully awake, and then more sedation is given, if required, to allow the suture to be adjusted.

The adjustable suture technique can be used with either a recessed or a resected rectus muscle. Adjustable suture surgery has also been successfully performed on the superior oblique tendon [9].

16.4Anesthetic and Analgesic Considerations

The choice of anesthesia is important if the suture adjustment is to be performed on the day of strabismus surgery. There are three key anesthetic considerations in adjustable suture surgery: (1) recovery of extraocular muscle function in time for assessment and adjustment; (2) patient comfort, alertness, and cooperation for postoperative motility assessment; and (3) sedation protocol for suture adjustment in patients unable to cooperate for adjustment.

16.4.1Recovery of Extraocular Muscle Function

For general anesthesia patients, extraocular muscle function recovers to normal by the time the patient has recovered sufficient alertness for postoperative assessment. When local anesthesia is used, longacting local anesthetics, such as bupivacaine, should also be avoided due to the lasting effect on extraocular muscle function. When shorter-acting local anesthetics, such as lidocaine, are used, a minimum of 5 h is required for motility to recover.

16.4.2Patient Comfort, Alertness, and Cooperation

for Postoperative Motility Assessment

16.4.2.1Premedication

One of the most commonly reported side effects of strabismus surgery is postoperative nausea and vomiting (PONV). Some studies have reported the inci-

dence to be two times greater in children than adults, ranging from 48 to 85% [11, 23]. It is imperative that the anesthesiologist attempt to minimize this risk to facilitate the postoperative eye examination and suture adjustment and to reduce the risk of aspiration and patient discomfort. Factors that influence PONV include the preoperative anxiety of the patient, anesthetic agents administered, and the use of opioids. Anesthesiologists can reduce the risk of PONV by avoiding emetogenic agents such as volatile anesthetics, nitrous oxide, opioids, etomidate, ketamine, and acetylcholinesterase inhibitors, and by administering anticholinergics, anxiolytics, and antiemetics.

16.4.2.2Induction and Maintenance

Induction with intravenous propofol is recommended

[4, 33]. Maintenance of anesthesia should preferably be maintained with short-acting intravenous agents, such as propofol or dexmedetomidine, because volatile anesthetics, such as halothane, isoflurane, and sevoflurane, may prolong emergence and/or cause emergence agitation and delirium [4, 33].

Muscle relaxants are not necessary during surgery, but they may facilitate the strabismus correction itself by making it easier for the surgeon to manipulate the extraocular muscles. If a muscle relaxant is used, a short-acting agent, such as mivacurium, which is rapidly metabolized by endogenous plasma cholinesterases and therefore does not require reversal agents, is recommended [33]. Longer-acting muscle relaxants may have residual neuromuscular blockade effects on the patient without the administration of reversal agents thereby delaying postoperative examination. The use of longer-acting muscle relaxants require reversal with acetylcholinesterase inhibitors and anticholinergics, which may also increase the incidence of PONV [11].

16.4.2.3Analgesia

Analgesia for strabismus surgery has presented anesthesiologists and ophthalmologists with several dilemmas. These patients clearly require analgesia both intraoperatively and postoperatively, but many opioid analgesics cause sedation, which makes accurate postoperative examination nearly impossible.

In addition, narcotics such as morphine increase the

incidence of PONV [11, 19, 24]. The administration of short-acting local anesthetics, such as topical tetracaine prior to emergence from anesthesia, may provide adequate analgesia without any associated side effects of narcotics [1]. Long-acting local anesthetics should be avoided, as noted above. If a parenteral opioid must be used, we recommend remifentanil, alfentanil, or fentanyl, which have a rapid onset and are short-acting. In patients with normal renal function, our preference is to use intraoperative ketorolac, which minimizes postoperative pain without concomitant sedation or PONV [19]. Ketorolac is probably most effective if given at the start of the procedure, but if there is concern about increased intraoperative bleeding, it may be given 30 min prior to the end of the surgery. For patients who will not require additional anesthesia for the suture adjustment, oral or rectal analgesics, such as acetaminophen in conjunction with an enteral opioid such as oxycodone, improve pain with less sedation and/or PONV than intravenous opioids [24].

Some anesthesiologists recommend using 65% nitrous oxide, although it can contribute to PONV, along with other intravenous anesthetics for maintenance of anesthesia during strabismus correction to reduce the use of other anesthetic agents that may prolong emergence [4, 11]. Anticholinergics administered preoperatively or at the time of induction, such as scopolamine, glycopyrrolate, or atropine, may provide several benefits both intraoperatively and postoperatively [12, 23]. They delay gastric discharge minimizing secretions, and may prevent the oculocardiac reflex. More importantly, administration of anticholinergics may decrease the incidence of PONV due to their antimuscarinic actions. High doses of anticholinergic agents may cause undesirable side effects, such as blurred vision, restlessness, and hallucinations. Benzodiazepines, such as diazepam, lorazepam, and midazolam also have many beneficial effects on the patient undergoing strabismus correction [4, 23]. They may not only decrease anxiety helping to facilitate either the insertion of peripheral venous catheters or the mask induction of anesthesia, but they may reduce the incidence of PONV as well.

Benzodiazepines should be administered judiciously, because high doses may also cause undesirable sedation postoperatively.

16.4.2.4Postoperative Nausea and Vomiting

Postoperative nausea and vomiting (PONV) is a major problem in some patients. Ondansetron, a 5-HT3 antagonist, is a very effective antiemetic with very few side effects, and therefore it should be given prophylactically to prevent PONV [25]. Additional antiemetics should also be considered for use both prophylactically and for symptomatic treatment of

PONV [11]. For example, dexamethasone, a potent synthetic glucocorticoid, may augment the antiemetic effects of ondansetron. Metoclopramide, a dopamine agonist and prokinetic, can also be used as an antiemetic after strabismus surgery, but in high doses it may cause extrapyramidal side effects including oculogyric crisis. Hydroxyzine, an antihistamine, may also provide relief of both perioperative anxiety and

PONV, and therefore may also be considered during the perioperative period.

16.4.3Sedation Protocol

for Suture Adjustment

For patients, mainly children, who will be unable to remain still during the suture adjustment, the anesthesiologist should be notified in advance of the possible need to provide additional anesthesia. These patients should be in a monitored setting such as the postanesthesia care unit or operating room. A quiet location, such as an isolation room or procedure room, away from the noise and bustle of a recovery room may help calm the patient and provide needed privacy. The recommended ASA standards for basic anesthetic monitoring and airway management should be strictly adhered to for patient safety regardless of the adjustment location.

Short-acting intravenous anesthetics that facilitate rapid emergence with minimal side effects, such as propofol, should be used. Often a full induction dose of propofol (1−3 mg/kg) is required to allow insertion of the eyelid speculum and manipulation of the adjustable sutures. Topical anesthesia with proparacaine or tetracaine is an important adjunct [1].

As with any general anesthetic administration, the anesthesiologist should remain at the bedside until emergence.

16.5 Surgical Technique

The surgery is performed under general or local anesthesia per surgeon preference. The adjustment is performed when the patient is fully awake or after the local anesthetic has worn off and the function of the muscle has returned to normal.

sutures. The ends of the noose suture are tied together to provide a bucket handle for manipulation of the noose during adjustment.

The surgeon has the option of adjusting the sutures intraoperatively, or postoperatively from 1 h to 1 week after surgery. Intraoperative adjustment allows for immediate correction of a major postoperative misalignment but is less likely to allow for more refined adjustment, which requires an alert patient. Adjustment is generally performed within 24 h because of

16.5.1 Limbal vs Fornix Approach

The limbal approach provides broad exposure during the surgery and suture adjustment. This approach requires conjunctival closure, as it is difficult to cover the suture knot with the conjunctiva after the adjustment.

The fornix approach includes a hidden incision underneath the eyelid with less scarring, thus producing excellent cosmetic results in most cases. Exposure is limited, which may increase the technical difficulty of surgery and suture adjustment. The fornix approach is more comfortable for the patient, as the sutures are covered. In some cases, no conjunctival closure is required.

16.5.2 Technique

There are two main methods for muscle reattachment:

1.Bow-tie technique (Fig. 16.1a). The sutures are passed through scleral tunnels and they are tied together in a single loop bow tie as with a shoelace. At adjustment, the bow is untied, the muscle position adjusted, and the bow retied. Once the desired alignment is obtained, the bow is cut and converted to a square knot.

2.Cinch or sliding-noose technique (Fig. 16.1b). The sutures are passed through scleral tunnels emerging less than 1 mm apart. A noose is created by tying a separate piece of suture around the scleral

Fig. 16.1  a Bow-tie technique: The sutures are tied together in a single-loop bow tie like a shoelace. b Sliding-noose technique: A noose is created by tying a separate piece of suture around the scleral sutures

irritation caused by the untied sutures protruding from conjunctiva. The exact timing of adjustment between 1 and 24 h is a matter of local logistics and surgeon preference. When the surgeon is satisfied with the adjustment, the sutures are firmly tied together to permanently secure the muscle. Surgeons who use larger conjunctival incisions often preplace the conjunctival sutures during the primary surgery and tie them off after the final adjustment [21].

16.5.3 Adjustable Sutures in Children

A variety of adaptations of the adjustable suture technique for use in children have been described. The sutures can be adjusted under topical anesthesia on the morning following surgery [3] or in the afternoon on the same day of surgery [5]. The “Releasable adjustable” suture technique allows the suture adjustment on the next day as an office procedure, using intranasal Midazolam and topical lidocaine 2% jelly [10]. The modified adjustable suture technique eliminates the necessity of further manipulation in children who do not require adjustment [6].

16.5.4 Semi-Adjustable Sutures

Muscle slippage is more likely when surgery is performed on the inferior rectus muscle, with an incidence of between 7 and 41%. This has been observed both in adjustable and non-adjustable cases [35].

Kushner described a “semi-adjustable” technique in an effort to secure the muscle more firmly to the globe, thus reducing the incidence of muscle slippage while preserving the potential for adjustment

[16]. The process involves suturing the corners of the muscle firmly to the sclera and placing the center of the muscle on an adjustable suture (Fig. 16.2). A trade-off of this procedure is that it limits the potential to increase the amount of recession at the time of adjustment. By targeting an initial overcorrection with placement of the corner sutures, this downside is limited.

Fig. 16.2  Semi-adjustable sutures showing that the corners of the inferior rectus muscle are sutured firmly to the sclera and the center of the muscle is placed on an adjustable suture. (From [16])

16.5.5Adjustable Superior Oblique Suture Spacer

The “superior oblique suture spacer” is a modification of Knapp’s [15] and Wright’s [34] technique which allows partial, reversible, and intraoperatively adjustable superior oblique weakening [28]. The technique uses a non-absorbable suture to separate the cut ends of the superior oblique tendon with precision. This allows the separation to be adjusted in a graded manner intraoperatively according to the exaggerated traction test and fundus torsion.

The major advantage of adjustable suture strabismus surgery is that it is believed to reduce the rate of reoperations by providing a chance to refine alignment in an alert patient; however, the surgery is complex, involving greater operating time plus the logistics of scheduling the adjustment. The procedure increases the amount of suture material left in the eye after the adjustment.There is increased patient anxiety, though the discomfort is generally minimal. Some patients are unable to cooperate for adjustment. To the great disappointment of patient and surgeon, despite all of the care taken to perfectly align the eyes at adjustment, there may still be a change in alignment as the eye heals, giving an unsatisfactory result.

16.7 Complications

Complications following the adjustable suture technique are rare. Intra-adjustment complications include nausea, vomiting, and ocular pain. An oculocardiac reflex and possible bradycardia may be associated with muscle manipulations; thus, some patients may experience syncope, lightheadedness, diaphoresis, or sense of temperature change. The risk can be reduced with reassurance, topical anesthesia, supine positioning, and avoiding an eyelid speculum. Cardiac monitoring during adjustment is not needed except in cases of heart disease and heart block.

Suture breakage and inability to adjust the muscle can occur. There may be persistence and irritation of the suture knot after adjustment, which cannot be safely removed until around 3 weeks after the surgery.

Mocan andAzar [20] have reported four patients who developed severe conjunctival dehiscence, requiring amniotic membrane transplantation, after strabismus surgery with adjustable sutures. Eustis and colleagues

[7] found a more robust tissue response to surgery in patients with adjustable sutures, with 4 of 30 (13%) patients developing suture granuloma and 2 (7%) patients with a sub-conjunctival infection.

In this section, the senior author’s preferred techniques for adjustable suture surgery, including the “short tag noose” suture, will be detailed. There are not necessarily any studies to support these preferences, but these are the approaches that have evolved through experience with mentors, colleagues, students, and, of course, patients.

The adjustable suture recession or resection surgery is performed under general anesthesia in all patients, if medically permissible. Despite excellent retrobulbar anesthesia, many patients are still quite uncomfortable with the sensation of pulling on the muscle. General anesthesia allows for assessment of the position of the eyes under anesthesia, a valuable tool in surgical planning in some cases [2]. It also allows for forced duction testing without concern for causing discomfort. Finally, general anesthesia obviates the need to wait for local anesthetic to wear off, allowing for earlier suture adjustment on the day of surgery, thus simplifying the logistics of the procedure.

In patients not medically appropriate for general anesthesia, subtenon’s irrigation of lidocaine is used. With this approach, the eye is anesthetized with proparacaine and prepped and draped. Four percent lidocaine hydrochloride (Xylocaine, Astra Zanaca, North Ryde, NW Australia) is drawn up into a 3-cc syringe capped with an irrigating (Randolph) cannula. The patient is sedated and a lid speculum is placed. A sharp Westcott scissors is then used to open the conjunctiva in the quadrant near the muscle. The cannula is advanced deep into the quadrant and 2 cc of anesthetic is injected.

Care is taken during surgery to maximize patient comfort in the postoperative period. Hydroxypropyl methylcellulose (Goniosol, Ciba Vision Ophthalmics, Duluth, Ga.) is placed over the cornea at intervals during the surgery to prevent the cornea from drying without need for frequent applications of normal saline.Afornix incision is preferred, keeping the incision size as small as possible. A Guyton muscle hook allows the muscle to be manipulated through a conjunctival incision as small as 1 cm. At each step, a minimum of tension is placed on the incision.

We prefer the sliding noose adjustable suture approach. The muscle is secured with a double-armed 6-0 polyglactin 910 (Vicryl, Ethicon, Somerville, N.J.) suture and disinserted from the sclera. The mus-

Fig. 16.4a−c  Tying an overhand knot. The straight arrows show the direction in which the sutures are passed/pulled in a sequential manner. a The empty needle holder is looped 360° in a clockwise direction around the sutures. b The suture ends are then grasped with the same needle holder and pulled through the loop. c The knot is tightened by pulling the suture taut

cle insertion is identified and grasped with 0.5 Castroveijo forceps. Spatulated needles from the sutures are passed one after the other, through the original insertion, at half-thickness depth. The needles are

passed in a “V” configuration (Fig. 16.3). For recessions, the scleral passes are separated by 1−2 mm when they enter sclera, but are nearly touching where they exit (Fig. 16.3a). For resections, where the muscle may be pulled up to the insertion at adjustment, this “V” separation is exaggerated to 3−5 mm at the entry site, but the sutures still nearly touch at the exit site (Fig. 16.3b).

For an adjustable recession, the standard hangback approach and surgical dosages are used. For an adjustable resection, an extra 1−3 mm of muscle is resected. The muscle is then allowed to hang back by the same amount. This allows for either advancement or recession of the resected muscle at adjustment. It also avoids the sometimes unsightly appearance of muscle tissue (rather than tendon) at the insertion site (Fig. 16.3b).

After the sutures are passed, they are pulled up so that the muscle is drawn up to the original insertion. These sutures are then secured to each other using an overhand knot (Fig. 16.4), with care being taken not to allow either pole of the muscle to fall back asymmetrically. The extra suture is cut just above the overhand knot. These joined sutures are called pole sutures. To apply the adjustable noose, the 5-cm fragment of polyglactin 910 suture is used. This piece of suture is placed underneath the pole sutures and wrapped around a second time (Fig. 16.5). A square knot is then tied to ensure a tight noose, which prevents inadvertent slippage. This is critical – the noose should be as tight as possible. The ends of this noose are tied together in an overhand knot as described above, using two needle holders to obtain a noose length distinctly shorter than the pole sutures. The extra suture above the overhand knot is trimmed. The noose is slid forward or back to the desired location. If the pole sutures are nearly touching where they exit, the noose is placed at the exact desired recession (e.g., 5 mm from the exit site for a 5-mm recession).

If the pole sutures are separated where they exit, an additional “fudge factor” is added (e.g., 5.5 mm for a

5-mm recession if the pole sutures exit 1 mm apart). The new muscle position is confirmed by measuring its distance from the scleral insertion.

A 5-0 polyester (Mersilene, Ethicon, Somerville, N.J.) traction suture is often placed, as it helps in manipulating the globe and retracting conjunctiva during suture adjustment. The first pass of the traction suture is perpendicular to the muscle insertion above the quadrant where the incision was made (Fig. 16.6a, pass 1), while the second pass is parallel and anterior to the insertion (Fig. 16.6a, pass 2). The two loose suture ends are then gathered into the left hand, along with the loop between the two passes, and a needle holder, held in the right hand, is positioned over the sutures (Fig. 16.6b).The loose ends are secured to each other with two overhand knots (Fig. 16.6c).

The sutures are tucked under the conjunctiva at the end of the surgery. The conjunctiva is not routinely sutured as the small incision self-seals under the eyelid; however, excess Tenon’s tissue should be excised to prevent the formation of conjunctival cyst or pyogenic granuloma. This can most easily be accomplished by copiously irrigating the incision with saline, then grasping and excising protruding tissue

(taking care to avoid any suture material). If the conjunctival incision has enlarged inadvertently during surgery, it is partly closed with a 6-0 fast-absorbing gut suture or 8-0 polyglactin 910 suture (Vicryl, Ethicon, Somerville, N.J.), burying the knots for comfort. The incision must be left large enough to allow for suture adjustment even if it is partially closed with sutures. An eye patch is not necessary unless there is an epithelial defect. Antibiotic/steroid drops are preferred over ointment to avoid blurring the vision during the adjustment. The long suture ends are folded and taped over the medial surface of the nose or just lateral to the lateral canthus with a half-inch steristrip.

For pediatric adjustable sutures where sedation will be required for adjustment, two steps are taken to avoid the need for sedation in case adjustment is not needed. Firstly, no polyester traction suture is placed. Secondly, the pole sutures and noose are trimmed and tucked under conjunctiva. An overhand knot is placed just 2−3 mm away from the suture exit site, allowing for an additional 2- to 3-mm recession while not leaving excessive suture material. The noose sutures are

Fig. 16.5a−c  Application of the noose. a A piece of suture is placed underneath the pole sutures and wrapped around a second time. The suture noose is tied using a square knot. c The ends of the noose are tied together in an overhand knot

also trimmed, but no overhand knot is placed so that they can be distinguished from the pole sutures. This has been described as the “short tag noose” technique

(Fig. 16.7) [18].

The adjustment is performed 1−2 h after surgery in the recovery room when the surgery is performed under general anesthesia. If local anesthesia is used, the adjustment should not be performed until at least 5 h have passed to give time for the local anesthetic effect to wear off. We also perform late adjustments up to 1 week after surgery in some cases.

To initiate the suture adjustment session, the steristrips are removed, and debris is cleaned from the eyelid. Topical anesthetic drops are instilled at least thrice at 2- to 3-min intervals. We prefer proparacaine over tetracaine, which causes severe stinging when first instilled. To assure that the patient is sufficiently alert, we ask the patient to sit without back support