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

Fig. 16.8a,b  Straight-edge test to assess for prism in spectacle lenses. a No prism present. Note that the table edge forms a single, continuous line through and between both lenses. b Vertical prism present. Note the presence of base-up prism in the left lens, causing the table edge to appear discontinuous

on the edge of the bed with legs dangling. The alignment is assessed with corrective lenses in place, if indicated. If the patient had required prisms preoperatively, care should be taken to assure that the glasses used during adjustment do not have prism! This can be verified by viewing a straight edge passing across the centers of the lenses (Fig. 16.8). For patients with high refractive error and prism glasses, we will prescribe prism-free glasses at the time surgery is scheduled. Those glasses may be used at the preoperative visit as well as during and after the adjustment. For patients with high refractive error who wear contact lenses, the alignment can be assessed by applying topical anesthesia and inserting the contact lenses for the adjustment session. The lenses are then removed and cleaned after the suture adjustment is complete.

Once the patient is positioned, ductions and versions are carefully assessed. Cover testing is performed at distance and near. Often, a transilluminator light must be used as a target if vision is blurred. The goal of adjustment in cases of esotropia and hypertropia is to achieve orthotropia. An exception is to undercorrect the superior oblique palsy patient who has had an inferior oblique weakening procedure in combination with a vertical rectus muscle recession. The goal of adjustment for exotropia cases is to overcorrect so that the patient is diplopic at distance

(ET 10−15 PD) with no shift at 0.33 m. The surgeon

should take extra time adjusting patients with large fusional amplitudes (>50 PD), who have a tendency to show a larger early overcorrection due to persistent fusional efforts. Non-fusing exotropia patients may be overcorrected more, especially cases of sensory exotropia. For vertical misalignments, it is harder to predict which way the muscle will drift. In our experience, recessions tend to increase as they heal, while resections tend to decrease in effect. Non-absorbable (e.g., polyester) sutures may be considered for large vertical rectus recessions, especially on the inferior rectus muscle if not using the “semi-adjustable” technique. When non-absorbable sutures are used, the patient should be counseled that the knot may eventually erode through conjunctiva and have to be removed.

In very young, less cooperative children we maintain NPO status in the recovery room with the IV left in place. We advise the anesthesiologist in advance about the possible need for sedation in the recovery room. Many children are initially fearful, but given enough time, reassurance, and proparacaine, they will eventually cooperate for adjustment. If not, the anesthesia team generally administers IV Propofol (see Section 16.4.3, Sedation Protocol for Suture Adjustment, p. 216).

To access the noose for an adjustment, the pole sutures are grasped first to avoid inadvertent sliding of the noose. To tighten or decrease the recession, the pole sutures are pulled up to draw the muscle anteriorly while the patient is asked to look toward the muscle (or, if the patient is sedated, the globe is rotated toward the muscle using a traction suture or forceps). This traction on the pole suture pulls the noose suture up and away from the sclera. The pole sutures are stabilized with a needle holder clamped in front of the noose and the noose is slid posteriorly to the sclera with another needle holder (Fig. 16.9a). To loosen or increase the recession, the pole sutures are again pulled forward with a needle holder, this time stabilizing the pole sutures by clamping behind the noose.

With the second needle holder, the noose is grasped and moved away from the muscle (Fig. 16.9b). Once the noose is adjusted, the sutures are released and the patient is asked to look toward the adjusted muscle while the eye held in place (or rotated away from the muscle if the patient is sedated). This will retract the muscle posteriorly and force the noose firmly against the sclera.

We use two approaches to complete the adjustment. To permanently secure the suture, the distal overhand knot is cut to separate the pole sutures.

The sutures are then firmly tied to each other. Care is taken not to pull up on the pole sutures while tying the sutures, as this may change the position of the muscle. Both pairs of polyglactin 910 sutures (pole and noose) are trimmed and the polyester traction suture is removed. The conjunctiva generally covers the suture ends without the need for closure.

A different completion step is used on the day of surgery to allow for readjustment up to 7 days later. A second overhand knot is tied on the pole suture to reduce its length to 2−3 mm. The noose sutures are then trimmed to a 5-mm length (we refer to this as the “short tag noose”) with no overhand knot (Fig. 16.7). The polyester suture is removed and the suture ends tucked under conjunctiva. In our experience, the sliding noose will not move during the healing period as long as it has been tied securely with a good square knot.

In most cases, we use the short tag noose to allow for later suture readjustment. If a non-absorbable pole suture is used, or if there is a desire to minimize the amount of suture material in the wound, then the suture is permanently secured and trimmed.

When suture adjustment is performed more than 24 h after surgery, it is slightly more uncomfortable for the patient than same-day or next-day adjustment. The conjunctiva should be anesthesized with a proparacaine-soaked cotton-tipped applicator or subconjunctival infusion of a small amount of 2% lidocaine. The conjunctival incision will have selfsealed by the time of the adjustment, so that it will be necessary to tease it open with forceps. If the muscle is firmly adherent to sclera, a muscle hook may be needed to gently separate the muscle from sclera and allow the muscle to be pulled forward or recessed. This is important to verify, as otherwise the noose may slide but the muscle will not move. The younger the patient, the sooner the muscle becomes firmly adherent to the globe. We have not been able to adjust children more than 2 days after surgery without sedation. Elderly patients will tolerate adjustment up to 1 week later. We have performed very late adjustments up to 2 weeks after surgery, but only in the OR with sedation. After 2 weeks, we do not recommend attempting an adjustment out of concerned that that the now-dissolving polyglactin 910 suture will break before the muscle has re-adhered to the globe.

Some surgeons find it easier to advance the muscle when it is over recessed rather than to further recess

Take Home Pearls

•The Q-tip test helps identify patients who are suitable for adjustable sutures.

•Keep the incision size as small as possible for maximum comfort and minimum scarring.

•Ensure a tight noose to prevent inadvertent slippage.

•Assure the patient is sufficiently alert for adjustment.

•The goal is not always straight eyes. Aim for orthophoria in esotropia and hypertropia. Overcorrect exotropia.

•Do not ignore your original numbers – it is possible to over-adjust back to no effect.

•There is no need to tie off a well-done cinch knot.

•For pediatric adjustable strabismus suture surgery, use the short tag noose approach to avoid the need for sedation when postoperative alignment is good.

the muscle when it is under recessed; however, using our preferred technique, we have found no difference in recession vs advancement.

When deciding whether to perform an adjustment, do not ignore our original numbers. It is important to recognize when to stop adjusting. Adjustments >2 mm should be avoided except in unusual cases such as severe restrictive strabismus. If there is no change in alignment after an adjustment, then other factors, such as orbital restriction or transient muscle weakness, are at play and there is no point in trying to adjust further.

We recently reviewed the results of our short tag noose adjustable technique [18] in 95 patients aged 2−83 years; of them, 81% had complex strabismus

(reoperation, muscle restriction, nerve palsy). The reoperation rate was 14% for horizontal and 20% for vertical strabismus. Eighteen percent of patients were adjusted >1 day after surgery, with an overall success rate of 85% for both horizontal and vertical strabismus and a reoperation rate of 0% for horizontal and

7% for vertical strabismus in that group.

16.11 Conclusion

Adjustable suture strabismus surgery makes sense intellectually, but validation studies to date are not uniformly compelling. Some studies suggest that the reoperation rate is as low as 10%. The target of the suture adjustment is not always straight eyes – the exact goal for postoperative alignment varies, and must be developed with time and experience. Our recent results indicate a reoperation rate of 14−20% in a referral practice of patients with complex strabismus; however, statistics may not be able to account for the “safety net” effect of being able to adjust when there is a big postoperative surprise. Adjustable sutures provide practical benefits to both the patient and the surgeon and have become preferable for adults and many young children. Adjustable sutures do not guarantee excellent results, but they can be useful when more than usual uncertainty exists about the expected degree of the correction.

References

1.Anninger W, Forbes B, Quinn G et al. (2007) The effect of topical tetracaine eye drops on emergence behavior and pain relief after strabismus surgery. J AAPOS

11:273−276

2.Castelbuono AC, White JE, Guyton DL (1999) The use of (a)symmetry of the rest position of the eyes under general anesthesia or sedation-hypnosis in the design of strabismus surgery: a favorable pilot study in 51 exotropia cases. Binocul Vis Strabismus Q 14:285−290

3.Chan TK, Rosenbaum AL, Hall L (1999) The results of adjustable suture technique in paediatric strabismus surgery. Eye 13:567−570

4.Cogen MS, Guthrie ME, Vinik HR (2002) The immediate postoperative adjustment of sutures in strabismus surgery with comaintenance of anesthesia using propofol and midazolam. J AAPOS 6:241−245

5.Dawson E, Bentley C, Lee J (2001) Adjustable squint surgery in children. Strabismus 9:221−224

6.Engel JM, Rousta ST (2004) Adjustable sutures in children using a modified technique. J AAPOS 8:243−248

7.Eustis HS, Elmer TR Jr, Ellis G Jr (2004) Postoperative results of absorbable, subconjunctival adjustable sutures.

J AAPOS 8:240−242

8.George ND (2003) Adjustable sutures: Who needs them?

Eye 17:683−684

9.Goldenberg-Cohen N, Tarczy-Hornoch K, Klink DF et al.

(2005) Postoperative adjustable surgery of the superior oblique tendon. Strabismus 13:5−10

10.Hakim OM, El-Hag YG, Haikal MA (2005) Releasable adjustable suture technique for children. J AAPOS

9:386−390

11.Haynes GR, Bailey MK (1996) Postoperative nausea and vomiting: review and clinical approaches. South Med J

89:940−949

12.Honkavaara P, Pyykko I (1999) Effects of atropine and scopolamine on bradycardia and emetic symptoms in otoplasty. Laryngoscope109:108−112

13.Jampolsky A (1975) Strabismus reoperation techniques. Trans Sect Ophthalmol Am Acad Ophthalmol Otolaryngol 79:704−717

14.Jampolsky A (1979) Current techniques of adjustable strabismus surgery. Am J Ophthalmol 88:406−418

15.Jampolsky A (1998) The Philip Knapp Lectureship. J AA-

POS 2:131−132

16.Kushner BJ (2004) An evaluation of the semiadjustable suture strabismus surgical procedure. J AAPOS 8:481−487

17.Kipioti A, George ND, Taylor RH (2004) Tied and tidy: closing the conjunctiva over adjustable sutures. J Pediatr

Ophthalmol Strabismus 41:226−229

18.Liang S, Loudon S, Salgado C et al. (2008) Short tag noose for optional, late suture adjustment in strabismus surgery (Abstract), J AAPOS 2008;12:102

19.Mendel HG, Guarnieri KM, Sundt LM et al. (1995) The effects of ketorolac and fentanyl on postoperative vomiting and analgesic requirements in children undergoing strabismus surgery. Anesthesia & Analgesia 80:1129–33

20.Mocan MC, Azar NF (2005) Amniotic membrane transplantation for the repair of severe conjunctival dehiscence after strabismus surgery with adjustable sutures. Am J

Ophthalmol 140:533−534

21.Nguyen DQ, Hale J, Lany H von et al. (2007) Releasable conjunctival suture for adjustable suture surgery. J Pediatr

Ophthalmol Strabismus 44:35−38

22.Ogut MS, Onal S, Demirtas S (2007) Adjustable suture surgery for correction of various types of strabismus.

Ophthalmic Surg Lasers Imaging 38:196−202

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24.Pradda GS, Cruz OA, Krock JL (1997) Comparison of postoperative emesis, recovery profile, and analgesia in pediatric strabismus repair. Rectal acetaminophen versus intravenous fentanyl-droperidol. Ophthalmology

104:419−424

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26.Spierer A (2000) Adjustment of sutures 8 hours vs 24 hours after strabismus surgery. Am J Ophthalmol 129:521−524

27.Strominger MB, Richards R (1999) Adjustable sutures in pediatric ophthalmology and strabismus. J Pediatr Ophthalmol Strabismus 36:112−117

28.Suh DW, Guyton DL, Hunter DG (2001) An adjustable superior oblique tendon spacer with the use of nonabsorbable suture. J AAPOS 5:164−171

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31.Tripathi A, Haslett R, Marsh IB (2003) Strabismus surgery: adjustable sutures-good for all? Eye 17:739−742

32.Velez FG, Chan TK, Vives T et al. (2001) Timing of postoperative adjustment in adjustable suture strabismus surgery. J AAPOS 5:178−183

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17.2Intraoperative Complications  . . . . . .   228

17.2.1Perforation of the Sclera  . . . . . . . .   228

17.2.2Management of Penetration

17.2.4Management of a Lost Muscle  . . . . .   230

17.2.5Slipped Muscle  . . . . . . . . . . .   231

17.2.6Operating on the Wrong Muscle

or Performing the Incorrect Procedure

on an Extraocular Muscle  . . . . . . .   232

17.3Immediate Postoperative Occurrences  . .   232

17.4Postoperative Infections and Inflammation    233

17.4.1Orbital Cellulitis  . . . . . . . . . . .   233

17.4.2 Myositis  . . . . . . . . . . . . . .   233

17.4.3Necrotizing Scleritis  . . . . . . . . .   233

17.4.4Endophthalmitis  . . . . . . . . . . .   233

17.6Delayed Postoperative Reactions  . . . .   236

17.6.1Foreign Body Granuloma  . . . . . . .   236

17.6.4Conjunctival Inclusion Cysts  . . . . . .   236

17.7.2Advancement of the Plica Semilunaris

17.7.4Changes in Refractive Error  . . . . . .   239

17.7.5Complications Related to Anesthesia  . . .   239 References  . . . . . . . . . . . . . . . . .   240

Core Messages

•Surgical complications are defined as a deviation from the normal postoperative course. Failure to cure is

not necessarily a complication and may result from variability or inaccuracy

of preoperative measurements.

•Scleral penetration or perforation is more likely to occur in smaller

eyes with thin sclera. Highly myopic eyes or eyes that have undergone cryotherapy also have thin sclera.

•A lost muscle is most likely to occur during a resection of the medial rectus muscle.

•Findings of endophthalmitis include lethargy, asymmetric conjunctival injection, eyelid swelling, and possibly fever within 4 days of surgery. The diagnosis is made when leukocoria secondary to vitritis is recognized.

•Anterior segment ischemia is a rare but potentially serious complication of

strabismus surgery, which occurs almost exclusively in adults who have undergone surgery on multiple rectus muscles.

of strabismus surgery may occur during surgery or at a later date, as a result of some intraoperative event. Complications can occur after a properly planned and well-executed procedure and do not necessarily imply a deviation in the standard of care.

17.2 Intraoperative Complications

The prompt recognition and appropriate management of complications that occur during strabismus surgery may obviate an untoward postoperative result.

17.1 Introduction

Complications following strabismus surgery have become less frequent with improvements in surgical techniques and instrumentation. Spatula needles, synthetic absorbable sutures, and direct visualization of the muscles with excellent lighting in the operating room all contribute to successful surgery. As with all surgery, the strabismus surgeon must be able to recognize and manage intraoperative and postoperative problems. Strabismus surgery is not an exact science and should not be described as such to patients and parents. Unsatisfactory postoperative alignment can usually be corrected or improved with intervention by refractive error correction, prism therapy, or additional surgery [1].

A surgical complication is defined as a deviation from the normal postoperative course. Surgery may be well executed without any complications but still fail. If the original purpose of surgery has not been achieved, under correction, overcorrection, or other unsatisfactory alignment may result. This is not a complication but a “failure to cure” [2]. Failure to cure in strabismus may result from variability or inaccuracy of preoperative measurements leading to the performance of inadequate or excessive amounts of surgical recession or resection. Other factors may predispose to surgical unpredictability, such as poor fusion, poor vision, and diplopia. In addition, secondary contracture of an operated muscle may result in postoperative changes in alignment. Complications

17.2.1 Perforation of the Sclera

During strabismus surgery a needle may penetrate the sclera and enter the suprachoroidal space and choroid, or perforate the retina and enter the vitreous cavity. A partialor full-thickness laceration of the sclera proximal to the muscle insertion may occur as the tendon is disinserted using scissors. Rarely, vitreous humor may be encountered following a full-thickness perforation.

A transient hyphema may be produced with deep passage of a needle attached to a fixation suture at the limbus. Fortunately, most scleral perforations do not result in serious injury to the eye and many are unrecognized both at the time of surgery and in the immediate postoperative period. Consequences of scleral perforation, however, may include reduced vision secondary to vitreous hemorrhage, retinal detachment, and endophthalmitis.

The true incidence of penetration of the globe beyond the sclera or perforation during strabismus surgery is difficult to ascertain. Estimates range from 10 to 2% [3, 4]. Many deep penetrations and perforations are not recognized when they occur and the low rate of serious consequences results in the under-re- porting of these surgical events. In a recent prospective study of 217 eyes undergoing strabismus surgery by residents and fellows the incidence of scleral penetration was 5.1% and the incidence of perforation

2.8% [5]. The surgeon’s experience was not related to the frequency of these complications. Penetrations beyond the sclera or perforations were more likely to occur with rectus muscle recessions than resections,

and horizontal rectus muscles were most frequently associated with penetrations and perforations when compared with vertical rectus and oblique muscles. The authors found that the S-24 needle was more frequently involved in the penetrations and perforations than other needles [5]. The S-14 or S-29 spatula needles are preferable because they are smaller and more suitable for surgery on children’s eyes.

Scleral penetration or perforation is more likely to occur in smaller eyes with thin sclera, so younger patients are more at risk. The mean age at surgery for patients who experienced perforations was 4.8 years in one study [5]. Children who have been treated with cryotherapy or laser photocoagulation for retinopathy of prematurity often have very thin sclera near the muscle insertions. The sclera is thinnest in the area behind the rectus muscle insertions in all eyes. This may be obvious at the time of surgery since retinal pigment epithelium may be visible as a blue area through the thin sclera. Highly myopic eyes may have extremely thin sclera and such eyes are at higher risk of perforation. Sudden rupture of a localized area of very thin sclera near the insertion in a myopic patient during a recession of the superior rectus muscle has been reported [7].

Previous extraocular muscle surgery also creates a higher risk for perforation [6]. A tight adherent muscle insertion is often found in patients with congenital fibrosis of the extraocular muscles, Duane retraction syndrome, and thyroid-related ophthalmopathy. In these cases it may be very difficult to pass a muscle hook beneath the insertion to separate the tendon and muscle from the globe. Furthermore, the muscle hook elevates the sclera into the path of the scissors and may result in a partialor full-thickness laceration of the sclera during tenotomy. Disinserting the muscle without using a muscle hook may actually be safer in such situations. Passage of a needle beneath the conjunctiva and lateral rectus muscle to place a traction suture may also result in scleral perforation.

the needle accelerates during passage. At times, the thin sclera posterior to the limbus will become darker blue in color following passage of the needle, indicating suprachoroidal hemorrhage. Perforation is detected when a visible gap in the sclera at the surgical site occurs. This may be associated with a strip of pigment or blood, and occasionally the extrusion of vitreous humor. Many cases of penetration and perforation are not recognized at the time of surgery and have no sequelae. A future indirect ophthalmoscopic retinal examination may reveal pigment accumulation within the retina or a chorioretinal scar, adjacent to the site where the muscle was attached to the sclera (Fig. 17.1).

Deep passage of sutures can best be avoided by having optimal visualization of the surgical field with good lighting and with the use of surgical loupes. Some surgeons prefer to grasp the spatula needle about one-third of the distance from the tip to allow control of the needle during passage through the sclera. This requires a release of the needle prior to advancement in cases where a long tunnel is preferred. Other surgeons prefer to grasp the needle twothirds or three-quarters back from the tip for a single passage. The needle can usually be visualized within the scleral tunnel. Positioning of the surgeon’s hands in cases of shallow orbits with small palpebral fissures may be difficult. A second muscle hook used to spread the muscle insertion is useful when suturing a tightly adherent muscle tendon prior to disinsertion. Some strabismus surgeons instill 2.5% phenylephrine at the beginning of the case both for hemostasis and

17.2.2Management of Penetration or Perforation of the Sclera

Deep penetration through the sclera into the choroid or retinal pigment epithelium should be suspected if

Fig. 17.1  Chorioretinal scar and localized granuloma 10 years following placement of posterior fixation suture using 5-0 braided Dacron. (Courtesy of R. Saunders)

dilation of the pupil in case indirect ophthalmoscopy is required during strabismus surgery.

If perforation is suspected, visualization of the retina is important. Recognition of penetration or perforation on indirect ophthalmoscopy warrants careful follow-up with repeat retinal examinations. Retinal consultation is helpful, particularly if elevation of the retina with fluid surrounding the surgical site is found [8]. Children have a formed vitreous and are unlikely to develop a retinal detachment following retinal injury during strabismus surgery. Larger lacerations of the sclera are more likely to result in a detached retina and require immediate intervention to close the wound. In some cases with uveal tissue prolapse, a scleral patch graph may be necessary [6]. In cases in which scleral perforation is recognized, local (topical and subconjunctival) and systemic antibiotics or even a drop of dilute povidone iodine may be administered to re-sterilize the wound.

17.2.3 Lost Muscle

During or following strabismus surgery a detached muscle may slip back and be “lost” posteriorly in the orbit. Plager and Parks reported that 67% of lost superior, inferior, and lateral rectus muscles were retrievable, while only about 10% of lost medial rectus muscles were located [11]. This complication can occur when the muscle or tendon is disinserted from the globe or during a resection when the muscle is transected. The preplaced sutures may not have incorporated sufficient tendon or muscle tissue and may release spontaneously or be cut inadvertently. A thin tendon or muscle may be released or cut with a muscle hook or may rupture spontaneously anywhere along its course. This most often occurs at the muscle tendon−junction. Rupture with mild traction is referred to as the “Pulled-in-Two” syndrome (PITS)

[12]. The PITS is more likely to occur in a patient with a tenuous attachment from previous surgery or in an elderly individual where there is atrophy of the tissue.

A lost muscle is most likely to occur during a resection procedure, particularly on the medial rectus muscle. Although any muscle may be lost, the inferior oblique muscle usually does not retract when it is disinserted and remains in the proximal

Tenon’s capsule. It can usually be distinguished by its fleshy appearance. The superior rectus muscle may be transected during a planned superior oblique tenectomy procedure when direct visualization is not achieved. A muscle may also be lost following surgery if it detaches from the sclera because of inadequate suture attachment or unrecognized suture weakness or placement of the suture within the muscle capsule without securing the tendon or tissue with a locking knot.

17.2.4 Management of a Lost Muscle

Oncethiscomplicationisrecognizedintraoperatively, planned steps must be taken to attempt to recover the muscle. This is the time for the surgeon to collect his thoughts, draw on his experience and overcome the anxiety or panic inherent in this situation. The medial rectus muscle in particular will most likely retract through Tenon’s capsule, particularly if dissection of the intermusclar membrane, check ligaments, and capsule have been extended posteriorly during preparation for muscle resection or detachment. Enlarging a limbal incision or converting a fornix incision to a limbal incision will aid in visualization. It is important to understand that the muscle will often retract into Tenon’s capsule along the orbital wall, and not “hug” the globe posterior to the equator. The rectus muscle pulley system and orbital check ligaments account for this. The conjunctiva is reflected and the

Tenon’s capsule grasped and advanced carefully with forceps. Using good overhead lighting and perhaps a head light, the global surface is visually inspected and the connective tissue carefully manipulated in an attempt to locate the potential space where the muscle capsule penetrated Tenon’s capsule. It is wise to avoid excessive dissection posteriorly, as violation of the orbital fat pad will result in excessive posterior scarring and adherence. Evoking bradycardia (oculocardiac reflex) following grasping and tugging on suspected muscle tissue may indicate that the muscle has been found [13]. Although immediate retrieval is desirable, a less experienced surgeon might decide to close the conjunctival incision and refer the patient to a strabismus surgeon experienced in the retrieval of lost muscles. During the postoperative period, the severed muscle may attach to the sclera posteriorly,

particularly if there was minimal dissection to isolate the muscle prior to it being “lost.” The absence of hemorrhage and edema may make the tissue planes more distinct when reoperation takes place approximately 1 week after the initial surgery.

If the retracted muscle is reattached to the sclera, it should be secured proximal to the original insertion. If it cannot be found, a transposition procedure is an option. A partial tendon transposition, such as an augmented Hummelsheim procedure or a modified Jensen procedure, will preserve anterior segment circulation [14]. Botulinum toxin injection to the antagonist of the lost muscle can further obviate operating on another rectus muscle. Surgical weakening of the antagonist is usually not necessary if the transposition procedure is done at the time the muscle is lost or shortly thereafter, since contracture has not yet occurred. Anterior transposition of the inferior oblique muscle has been used successfully to replace a lost or damaged inferior rectus muscle [15].

Alost muscle may be recognized in the postoperative period if there is a large deviation with limited or absent ductions in the field of action of a recently operated muscle. The sutures used for attachment to the sclera may detach spontaneously or rarely following trauma. Patients may also present with clinical findings suggestive of a lost muscle and a history of strabismus surgery. In these circumstances, a surgical plan including preoperative orbital imaging may be of some benefit [16].

Demer and co-workers devised a strategy to improve the retrieval of a lost or transected muscle utilizing orbital imaging to visualize the anatomy and function of the extraocular muscles [17]. Multipositional magnetic resonance imaging (MRI) demonstrates contraction and relaxation by comparison of the muscle’s cross-sectional area in various positions. If contractility can be demonstrated, the authors suggest performing an orbitotomy along the adjacent wall if the muscle is located posteriorly, or a direct conjunctival approach if the imaging localizes the muscle anteriorly. If there is no contractility demonstrated, a transposition procedure may be a better option [18].

Alternatively, computed tomography (CT) images obtained with 2-mm-thick coronal and axial cuts using a spiral scanner may help to localize a lost muscle.

A technique to locate a lost muscle using a 3-di- mensional image guidance system (LandmarkX System, Xomed, Jacksonville, Fla.) originally designed

for neurosurgical procedures has been described. The CT images are loaded into the image guidance system. Using a transnasal endoscopic approach, the guidance probe is used to locate the muscle. The muscle can be secured with sutures and reattached to the globe [19]. It is important to understand that this type of surgical manipulation may disturb the retroorbital fat and connective tissue, resulting in postoperative scarring with limitation of muscle function even when the muscle is found and reattached.

17.2.5 Slipped Muscle

A previously operated muscle may slip posteriorly from its intended attachment site during the postoperative period. The muscle retracts within its capsule, while the muscle capsule remains attached to the new insertion site. This complication may result if the sutures do not adequately secure the tendon or muscle prior to tenotomy. The suture may only include muscle capsule if the full-thickness locking passes do not include muscle tissue. Postoperative trauma to the surgical site may also result in a slipped muscle [20].

A typical patient will present with muscle weakness and an unexpected postoperative strabismus. There is a duction deficit with limited rotations and reduced saccades in the field of action of the involved muscle. The duction limitation is not as pronounced as in a case of a lost muscle (Fig. 17.2). The resulting over-correction of the strabismus is usually not anticipated by the surgeon. Reoperation is usually necessary to correct the problem, and to prevent additional retraction and contracture of the antagonist muscle. It is difficult to confirm the location of the muscle with imaging. Intraoperatively the translucent muscle capsule may be identified as being attached to the sclera at the intended insertion site. There may be partial slippage of the muscle tissue within the capsule resulting in an asymmetric attachment. During surgical exploration the capsule should be followed posteriorly since muscle tissue or tendon may be contained within it.

Jampolsky described a “see-through test,” in which a muscle hook is easily visible behind a muscle capsule from which muscle tissue has detached [21]. The capsule may present as a pseudotendon and only with gentle posterior placement of an additional muscle

Fig. 17.2  a Child with slipped muscle postoperatively showing a right face turn following recession of left medial rectus muscle. b The same patient with a left exotropia present in primary-gaze position. c Poor adduction of the left eye in right gaze indicating a slipped left medial rectus muscle. d Normal horizontal versions in right gaze

hook will the true insertion of the slipped muscle be localized. Sutures may be passed and locked through the capsule while the true tendon is searched for if there is difficulty identifying the muscle. Sliding a muscle hook posteriorly between the capsule and the sclera is another useful technique to locate muscle tissue. Using this “step test” a bump or step is found at the junction of the muscle capsule and true tendon

[21]. Once found, the slipped muscle is secured and advanced. The actual reattachment site may vary according to the surgeon’s preference and the measured deviation. Additional strabismus surgery may be required in the future as there is less predictability of results following repair of a slipped or lost muscle.

17.2.6Operating on the Wrong Muscle or Performing the Incorrect Procedure on an Extraocular Muscle

Strabismus surgery may be performed on a muscle not included in the original surgical plan. There may be an anomalous extraocular muscle insertions or agenesis as is found in some patients with craniosynostosis [22, 23]. Improper placement or lack of a traction suture may result in rotation of the globe such that the anatomic muscle insertions are rotated. In such a case the surgeon may incorrectly believe that he or she is operating on the intended muscle. The superior oblique tendon may be confused with the superior rectus tendon and the wrong muscle operated on especially with poor visualization of the operative field.

Lack of attention to detail may result in a muscle being resected when the intention is to perform a recession, or vice versa. These events are all less likely to occur if the surgeon confirms the planned procedure during the preoperative “time out” which is being utilized in most operating rooms to avoid operating on the wrong eye or perhaps the wrong patient.

The surgeon should analyze the causes for an unexpected result and explain to the patient that in many cases, reoperation can correct an untoward result.

17.3Immediate Postoperative Occurrences

In the immediate postoperative period a corneal abrasion can produce severe pain and should be treated with patching. A retained foreign body (suture, cotton fiber, eyelash) can cause postoperative pain and a foreign body sensation.

Hemorrhaging into a muscle may produce a temporary underaction or spasm with a resultant limitation in the field of action of the involved muscle. This may mimic a slipped or lost muscle, but local hemorrhagic edema will help in recognizing this occurrence. Normal ductions will usually return in a few days once the edema and hemorrhage subside.