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

of the lids produced abnormal movement of the right globe. The adhesions were easily severed and anomalous movements improved. The authors recommended performing eyelid surgery and strabismus surgery in sequential operations rather than simultaneously to avoid this complication.

26.7 Preseptal Cellulitis

Preseptal cellulitis is discussed in detail in Chap. 22. Postoperative cellulitis has been estimated to occur at a frequency of 1 in 1100 strabismus operations [14]. We have learned that when a parent or patient calls with a concern about redness in the immediate postoperative period to ask them specifically about redness and swelling of the eyelids. Significant redness and swelling of the eyelids is very unusual following uncomplicated strabismus surgery and is often (if not usually) a sign of postoperative preseptal cellulitis (>Fig. 26.11). Systemic antibiotics are warranted. Though some reports have recommended hospitalization with intravenous antibiotic administration for treatment of postoperative cellulitis [14], most patients we have treated with preseptal cellulitis and no signs of orbital involvement after strabismus surgery were effectively managed in an outpatient setting with oral and/or intramuscular antibiotics. Patients with advanced ocular signs or symptoms, and/or constitutional signs including fever, reduced appetite, and/or lethargy, and patients who fail to improve after 24 h of outpatient therapy should be considered for admission and intravenous antibiotics.

Careful anterior segment examination and indirect ophthalmoscopy are indicated following administration of dilating drops to rule out concurrent intraocular infection. We have not seen intraocular infection in association with preseptal cellulitis, but we believe that the risk of intraocular infection may be higher in this setting and this concern has been raised by Parks [15]. The choice of antibiotics depends upon the age of patient and the local microbial spectrum. In some areas of the country, methicillin-resistant Staphylococcus aureus represents the bulk of serious staphylococcal infections, including com- munity-acquired infections, and clindamycin is often the drug of choice. Moxifloxacin is a reasonable consideration because of its ability to penetrate the blood–ocular barrier at therapeutic levels [16].

26.8 Eyelid Ecchymosis and Hematoma

Eyelid bruising and hematoma formation following strabismus surgery is unusual. It occurs most commonly in our experience following surgery on the inferior oblique muscle and following prolonged, complex reoperations, especially involving manipulation in the posterior aspect of the orbit (>Fig. 26.12). Eyelid ecchymosis and hematoma formation is generally benign and self-limiting. Severe hemorrhage and hematoma formation in the upper eyelid can cause damage to the levator aponeurosis with resulting ptosis. We have seen prolonged discoloration of the eyelid related to a hematoma in one patient lasting several months and producing great distress in the child’s family. Hemorrhage after strabismus surgery, including eyelid hemorrhages, is discussed in detail in Chap. 24.

26.9 Burns

Thermal burns to the ocular adnexa during eye surgery are rare, but have been reported. There are several potential sources of thermal injury in an operating room. Supplemental oxygen that gathers under the surgical drapes in high concentrations can lead to fires when cautery is used [17]. The use of compressed air rather than oxygen has been suggested as a method to reduce fire hazard during ophthalmologic procedures [18].

Inadvertent burns of the eyelids can also occur during attempted cautery of other ocular structures if the cautery device comes in contact with the skin. This is most likely to occur with use of thermal cautery, and is generally mild. Other, more unusual causes of burns are also possible. For example, we performed transillumination of the globe through the eyelids in a patient after surgery for reasons unrelated to her strabismus surgery. Our standard transilluminator was not available, prompting use of the fiber-optic attachment on the operating room headlamp. The surgeon first touched the end of the fi- ber-optic light source to confirm that it was not hot. Noting that it was completely cool, it was then placed on the skin of the lateral canthal area and used to transilluminate the globe. Upon completion of this procedure, small round burns were noted on the skin in the lateral canthal area. This prompted the

Fig. 26.11. Preseptal cellulitis of the right upper eyelid that developed 3 days after uncomplicated horizontal rectus muscle surgery

Fig. 26.12. Eyelid ecchymosis following surgery on the inferior oblique muscle

surgeon to hold the tip of the fiber-optic light source against his own hand for several seconds, after which it became immediately apparent that prolonged contact with this otherwise cool light source results in the production of a great deal of heat. Our patient healed without sequelae, and an important lesson was learned.

References

1.Pacheco EM, Guyton DL, Repka MX (1992) Changes in eyelid position accompanying vertical rectus muscle surgery and prevention of lower lid retraction with adjustable surgery. J Pediatr Ophthalmol Strabismus 29:265–272

2.Meyer DR, Simon JW, Kansora M (1996) Primary infratarsal lower eyelid retractor lysis to prevent eyelid retraction after inferior rectus muscle recession. Am J Ophthalmol 122:331–339

3.Helveston EM (1986) Pediatric ophthalmology and strabismus. Transactions of the New Orleans Academy of Ophthalmology. Raven, New York, pp 61–70

4.Kushner BJ (2000) The effect of anterior transposition of the inferior oblique muscle on the palpebral fissure. Arch Ophthalmol 118:1542–1546

5.Jampolsky A (1986) Management of vertical strabismus. In: Transactions of the New Orleans Academy of Ophthalmology. New Orleans Academy of Ophthalmology. Raven, New York, pp 154–157

6.Patel MP, Shapiro MD, Spinelli HM (2005) Combined hard palate spacer graft, midface suspension, and lateral canthoplasty for lower eyelid retraction: a tripartite approach. Plast Reconstr Surg 115:2105–2114; discussion 2115–2117

Chapter 26

7.Ohba M, Ohtsuka K, Hosaka Y, Ogawa K, Osanai H (2004) A case of a slipped medial rectus muscle after strabismus surgery. Binocul Vis Strabismus Q 19:165–168

8.Bloom JN, Parks MM (1981) The etiology, treatment and prevention of the “slipped muscle”. J Pediatr Ophthalmol Strabismus 18:6–11

9.Sprunger DT (1997) Recession of both horizontal rectus muscles in Duane syndrome with globe retraction in primary position. J AAPOS 1:31–33

10.Foster RS (1997) Vertical muscle transposition augmented with lateral fixation. J AAPOS 1:20–30

11.Lagréze WA, Gerling J, Staubach F (2005) Changes of the lid fissure after surgery on horizontal extraocular muscles. Am J Ophthalmol 140:1145–1146

12.McGhee CN, Dean S, Danesh-Meyer H (2002) Locally administered ocular corticosteroids: benefits and risks. Drug Saf 25:33–55

13.Simpson WA, Downes RN, Collin JR (1989) Unusual complication of strabismus and lid surgery. Ophthalmol Plast Reconstr Surg 5:131–132

14.Kivlin JD, Wilson ME Jr. (1995) Periocular infection after strabismus surgery. The Periocular Infection Study Group. J Pediatr Ophthalmol Strabismus 32:42–49

15.Parks MM (1989) Routine antibiotic coverage in eye muscle surgery [letter]. Binocular Vision Q 4:152–153

16.Hariprasad SM, Shah GK, Mieler WF et al (2006) Vitreous and aqueous penetration of orally administered moxifloxacin in humans. Arch Ophthalmol 124:178–182

17.Ho SY, French P (2002) Minimizing fire risk during eye surgery. Clin Nurs Res 11:387–402

18.Neatrour GP, Lederman IR (1989) Reducing fire hazard during ophthalmic surgery by using compressed air. Ophthalmic Surg 20:430–432

Most strabismus operations are straightforward and are performed without serious complications or surprises. Despite this, there are many situations the strabismus surgeon may encounter that are not so straightforward. Abnormal and/or unexpected anatomical issues may be anticipated prior to surgery or they may be unanticipated and first discovered intraoperatively. The purpose of this chapter is to review some of the more common scenarios that may be encountered before and during strabismus surgery that may alter management options.

27.1Congenital Aplasia

of the Extraocular Muscles

Anomalous embryologic development of mesodermal tissues around the eye can result in agenesis of extraocular muscles. The inferior rectus, inferior oblique, and the inferior portion of the lateral rectus muscle are thought to originate from a common inferior mesodermal complex embryologically. The remaining extraocular muscles, including the levator palpebrae superioris, are thought to be derived from a superior mesodermal complex [1]. Congenital aplasia and hypoplasia of each of the extraocular muscles has been reported. Congenitally absent muscles have been reported most commonly in patients with craniofacial dysostosis syndromes and chromosomal abnormalities. However, the condition can occur in otherwise healthy individuals and is not always recognized preoperatively. Strabismus surgery on patients with absent or hypoplastic extraocular muscles can be complex. Nonstandard surgical techniques, such as transposition procedures and suspension procedures, are often required. This discussion will begin with a review of muscle abnormalities in patients with craniofacial syndromes and be followed by a review of management options for specific muscle abnormalities.

27.2 Craniofacial Dysostosis Syndromes

Strabismus is common in patients with craniofacial syndromes. Strabismus in this patient subset is often atypical. Patients may have both horizontal and vertical deviations and commonly

have marked apparent overaction and/or underaction of the oblique muscles. Strabismus in this patient subset can occur due to a combination of one or more factors including muscle disturbance created by abnormal orbital anatomy, paralytic strabismus, and absent or hypoplastic extraocular muscles. In addition, orbital anatomy is often so abnormal that the rectus muscle paths are altered [2] and the trochlea of the superior oblique muscle may be abnormally located [3] (>Fig. 27.1).

All six extraocular muscles have been reported as congenitally absent or hypoplastic in patients with craniofacial syndromes [4–6]. Coats and coworkers [5] reported a patient with congenital absence of 11 of the 12 extraocular muscles. They pointed out that ophthalmic surgeons only surgically manipulate the distal aspect of the extraocular muscles and that true absence of the entire muscle can only be determined through neuroimaging of the orbits. Because any of the extraocular muscles or multiple muscles may be congenitally absent or hypoplastic in patients with craniosynostosis, Greenberg and Pollard [6] recommend limited exploration of all of the extraocular muscles during surgery to repair strabismus in patients with craniosynostosis.

Generally speaking, standard surgical techniques may be less effective in the treatment of strabismus associated with craniofacial syndromes. Coats and coworkers [5] reported lack of effectiveness of several operations that had been attempted to correct V-pattern strabismus with severe oblique dysfunction in patients with craniofacial syndromes. Among 14 patients who underwent 16 operations, including medial rectus muscle infraplacement, inferior oblique recession, inferior oblique myectomy, inferior oblique anterior transposition, and inferior oblique denervation/extirpation, all patients had significant residual ocular motility disturbances. Denervation and extirpation of the inferior oblique muscle and inferior oblique myectomy of the overacting inferior oblique muscles offered the best, but still suboptimal, improvement. Agenesis of the superior oblique tendon appeared to be the cause of severe inferior oblique overaction in a large proportion of affected patients. Stager and coworkers [7, 8] reported the use of nasal and anterior transposition of the inferior oblique muscle insertion to correct recurrent inferior oblique overaction, including that associated with agenesis of the superior oblique tendon (Chap. 11).

The timing of strabismus surgery relative to craniofacial surgery depends upon the age of the child, condition, and the

opinion and experience of the surgeon. On the one hand, craniofacial surgery can and often does alter ocular alignment; hence, some surgeons prefer to defer strabismus surgery until craniofacial surgery has been completed. On the other hand, it is more likely that a patient will attain binocularity if strabismus surgery is performed early; hence, some surgeons prefer to perform strabismus surgery as early as possible, even if this means performing surgery prior to completion of craniofacial surgery. The surgeon and patient should recognize that additional strabismus surgery may be required later if ocular alignment is altered by the future craniofacial surgery. A compromise approach might be to perform surgery early if the patient presents for ophthalmologic evaluation early in life. If the patient presents in later childhood or adulthood, deferring surgery until craniofacial surgery has been completed may be optimal, since the chance of obtaining binocularity is reduced in older age groups. Strabismus can negatively impact an already difficult situation for affected patients, and we have been willing to perform surgery prior to completion of craniofacial surgery even in late presenting patients when the patient desires earlier treatment.

Experience has demonstrated that a formula or cookbook approach to the management of strabismus in patients with congenital absence of more than one extraocular muscles is not feasible. The surgeon is left with a decision on how to maximally transfer remaining functional extraocular muscles to improve the patient’s ocular motility status, taking care to ensure that adequate anterior segment circulation is main-

tained and the patient is not put at excessive risk for anterior segment ischemia. Greenberg and Pollard [6] pointed out that some evidence exists that collateral anterior segment blood flow is reduced in patients with absent rectus muscles. We and others [9] have seen intact anterior ciliary vessels traveling in Tenon’s fascia and on the sclera in the area of the missing rectus muscles with these vessels ultimately entering the sclera in an area near the position where the missing muscle would have inserted, suggesting the presence of some degree of anomalous anterior segment circulation even when an extraocular mus­ cle is congenitally absent. The true nature of anterior segment circulation in patients with absent or hypoplastic extraocular muscles is unclear.

27.3Aplasia of the Superior Oblique Muscle and/or Tendon

The anatomy and function of the superior oblique muscle and tendon is more complex compared to the remaining five extraocular muscles. The presentation of congenital absence of the superior oblique muscle is variable and it may be impossible to make this diagnosis on clinical grounds alone. Chan and Demer [10] reported on the features of patients with congenital absence of the superior oblique muscle, which they confirmed was absent with orbital imaging in six patients. They compared patients with congenital absence of the superior oblique mus-

cle to patients with clinical evidence of a superior oblique palsy but with demonstrable superior oblique muscles on orbital imaging studies. Amblyopia was not present in any of their patients with unilateral absence of the superior oblique muscle. The mean incomitance of the hypertropia on head tilt testing and during lateral gaze overlapped the values of patients who had demonstrable superior oblique muscles present. Only one of the patients had concurrent horizontal strabismus. In contrast, Wallace and von Noorden [11] reported horizontal strabismus in seven of nine patients with congenital absence of the superior oblique muscle and Helveston and coworkers [12] reported concurrent horizontal strabismus in five of six patients.

Wallace and von Noorden [11] published an algorithm for the surgical management of strabismus caused by the absence of the superior oblique muscle and/or tendon. No single procedure is appropriate for all patients and the surgical decision is based upon several factors including size of the vertical deviation, degree of excyclotorsion, concurrent horizontal strabis-

Fig. 27.2. Algorithm for the surgical management of strabismus caused by absence of the superior oblique muscle and/or tendon. (Reprinted from American Journal of Ophthalmology, volume 118, Wallace DK, von Noorden GK, Clinical characteristics and surgical management of congenital absence of the superior oblique tendon, pp 63–69, copyright 1994, with permission from Elsevier [11])

mus, and the degree of comitance (>Fig. 27.2). In addition to the scheme proposed by Wallace and von Noorden, Stager and co-workers [8] reported anterior and nasal transposition of the inferior oblique muscle (Chap. 11) to successfully treat patients with congenital absence of the superior oblique muscle, after failure of inferior oblique recession alone to adequately normalize ocular versions.

27.4 Aplasia of the Inferior Oblique Muscle

Aplasia of the inferior oblique muscle is uncommon. We have only seen aplasia of the inferior oblique muscle in association with absence of other extraocular muscles [5]. Reports on the surgical management of this condition are not available and the surgeon should devise an individualized surgical plan to logically correct the patient’s deviation, taking into account the possible presence of other extraocular muscle abnormalities.

27.5 Aplasia of the Inferior Rectus Muscle

Aplasia of the inferior rectus muscle can be unilateral or bilateral. Though generally sporadic, it can occur in association with craniofacial syndromes and can be familial, even in otherwise healthy individuals. Pimenides and coworkers [13] reported aplasia of the inferior rectus muscles in a mother and her two children who had no signs of craniofacial dysostosis. Astle and coworkers [14] reported three otherwise normal patients with bilateral congenital absence of the inferior rectus muscle (>Fig. 27.3). The patients presented with marked inability to depress the involved eye(s) in abduction, often with A-pattern esotropia and a chin-down head posture. A neuroimaging scan is helpful when the diagnosis is suspected and readily demonstrates absence of the inferior rectus muscle(s) (>Fig. 27.4).

Strabismus produced by an absent inferior rectus muscle is similar to that produced by paralysis of the inferior rectus muscle. Von Noorden and Hansell [15] reviewed the clinical characteristics and differential diagnosis in inferior rectus muscle paralysis. Presenting signs and symptoms included a highly incomitant vertical deviation, worse in the position of action

Fig. 27.4. Agenesis of the inferior rectus muscle is obvious on magnetic resonance imaging scan {Reprinted from Journal of AAPOS, 7, Astle WF and coworkers, Congenital absence of the inferior rectus muscle – diagnosis and management, pp 339–344, Copyright (2003), with permission from the American Association for Pediatric Ophthalmology and Strabismus [14]}

of the inferior rectus muscle, diplopia, and a head posture that consisted of a face turn with or without a head tilt. The head tilt was toward the paretic or paralyzed side in most, but not all, patients. They corrected the deviation with several procedures, which included inferior rectus resection and superior rectus recession in various combinations with other procedures and with contralateral superior oblique recession in one patient.

While a recession/resection surgery may be effective for an inferior rectus muscle paresis, a transposition procedure involving partial or complete transfer of the medial and lateral rectus muscle insertion to the inferior aspect of the globe is usually required [16, 17]. The tendons of the medial and lateral rectus muscles are transposed to a position where the missing inferior rectus muscle would have inserted (>Fig. 27.5). The transposition procedure may be augmented using posterior fixation sutures (Chap. 13), if desired. Botulinum toxin can be administered to the antagonist superior rectus muscle for added surgical effect, though temporary ptosis is common postoperatively [14]. Gamio and coworkers [18] reported on the use of inferior oblique recession and anterior transposition to successfully treat three patients with absent inferior rectus muscles.

27.6 Aplasia of the Superior Rectus Muscle

Aplasia of the superior rectus muscle has been reported less frequently than aplasia of the inferior rectus muscle. Mather and Saunders [9] reported bilaterally absent superior rectus muscles in a child who appeared clinically to have a double elevator palsy. The child had abnormal eye movements consisting of paradoxical depression of the abducting eye on attempted elevation of the adducting eye. These authors suggested that absence of the superior rectus muscle should be considered when paradoxical eye movements are seen with attempted up gaze in patients exhibiting severe limitation of elevation.

Alignment of the eyes in the primary position can be achieved with transposition surgery. Two basic approaches can be considered. Mather and Saunders [9] successfully utilized a modified Jensen procedure in which the superior halves of the horizontal rectus muscle bellies were united using synthetic absorbable sutures without disinsertion of these muscles (>Fig. 27.6). Rattigan and Nischal [19] reported use of a transposition procedure of the medial and lateral rectus muscles superiorly with posterior fixation suture augmentation to treat three patients with craniofacial syndromes and a primary position hypotropia due to absence or severe thinning of the superior rectus muscle. They noted at the time of surgery that two of the patients had “massive subconjunctival fibrosis,” despite the fact that none of the patients had undergone previous strabismus surgery.

27.7 Aplasia of the Horizontal Rectus Muscle

Isolated aplasia of the horizontal rectus muscles has been reported infrequently. One or multiple [20] horizontal rectus muscles may be congenitally absent. The condition can occur in association with craniofacial syndromes and chromosomal abnormalities. Keith and coworkers [21] reported the absence of the right lateral rectus muscle and hypoplasia of the left lateral rectus muscle in a patient with duplication of the long arm of chromosome 7. Coats and coworkers [22] also reported hypoplasia of the lateral rectus muscles in a patient with partial duplication of the long arm of chromosome 7.

A patient with isolated aplasia of a horizontal rectus mus­ cle presents with horizontal strabismus in the primary position and marked reduction or inability to move the eye in the direction of the absent muscle. When the primary position deviation is only moderate, a standard full tendon or partial tendon transposition procedure can be effective [23]. Posterior fixation suture augmentation or botulinum toxin injection

Fig. 27.5. The tendons of the medial and lateral rectus muscles are transposed to a position near to where the missing inferior rectus muscle would have inserted

Fig. 27.6. Modified Jensen-type transposition procedure, involving partial transposition of the horizontal rectus muscles without disinsertion to treat absence of the superior rectus muscle

to the antagonist muscle may be required to achieve optimal alignment. Standard, simultaneous recession of the antagonist muscle may be contraindicated because of the potential to compromise anterior segment circulation through simultaneous disruption of remaining anterior ciliary arteries in an eye with already disturbed anterior segment circulation. In longstanding cases, the primary position deviation can be large and severe limitation of ocular ductions may be present due to contracture of the antagonist. Standard strabismus surgery may not be adequate to achieve alignment in the primary position. We successfully treated a patient with hemifacial microsomia and congenital absence of the right lateral rectus muscle using a periosteal flap as a tether (Chap. 15) combined with extirpation of the anterior two-thirds of the patient’s contracted medial rectus muscle. The patient had an esotropia greater than 100 prism diopters preoperatively and could not abduct the involved eye beyond its fixed position in adduction.

27.8Abnormal Muscle Paths

and Heterotopic Rectus Muscle Pulleys

Magnetic resonance imaging has been increasingly used to assess the extraocular muscle paths and rectus muscle pulley position in the evaluation of atypical strabismus. A large body of evidence has been published on the topic of heterotopic rectus muscle pulleys as the cause of many atypical and even some common strabismus patterns. Heterotopic rectus muscle pulleys have been reported to be the true cause of such varied conditions as some cases of Brown syndrome [24], incomitant strabismus [25], and apparent oblique muscle dysfunction [26]. While not practical or necessary for the routine management of strabismus, high resolution magnetic resonance imaging can be helpful in selected patients with unusual strabismus [27].

Chapter 27

inferior oblique muscle might alter the physiologic action of the muscle. Surgeons should be aware of the potential for the double-bellied inferior oblique muscles to be found at surgery and ensure that the entire muscle is disinserted at its origin or residual inferior oblique muscle action caused by the residual, undisturbed portion of the muscle may persist postoperatively, resulting in residual unwanted ocular misalignment. Postoperative traction testing, often suggested as the best way to ensure that the inferior oblique muscle has been completely disinserted, may not be sufficient to detect a small residual band of intact inferior oblique muscle [29] (>Fig. 27.7). We have been seen double-bellied inferior oblique muscles and multiple inferior oblique muscle insertions less frequently than reported by Deangelis and Kraft. However, in a cadaver study involving 200 eyes, Emmel and coworkers [30] found bifid or trifid inferior oblique muscle insertions in about 50% of cases. In the normal course of surgery to isolate the inferior oblique muscle, we believe that it is likely that the entire inferior oblique muscle is usually readily hooked and that the surgeon may not even recognize the presence of a double-bellied inferior oblique muscle since the entire muscle, including both bellies, is contained and compacted on a hook.

27.9.2 Superior Oblique Muscle/Tendon

Helveston and coworkers [31] have reported variation in the anatomy of the superior oblique tendon in patients with congenital superior oblique palsy (>Fig. 27.8). In addition to redundant and absent superior oblique tendons, the tendon may insert on the nasal side of the superior rectus muscle or into

27.9 Abnormal Extraocular Muscle Insertions

Extraocular muscle insertions have been reported to be abnormally anteriorly or posteriorly located on the globe, to have multiple attachments to the globe, and to have other unusual variations. Abnormalities of extraocular muscle origins, on the other hand, have rarely been reported. The lack of reports of muscle origin abnormalities may reflect the fact that surgeons typically encounter only the distal aspect of the muscle surgically, rather than a true paucity of abnormalities involving the extraocular muscle origins.

27.9.1 Inferior Oblique Muscle

Deangelis and Kraft [28] reported finding a double-bellied inferior oblique muscle insertion in 10.9% of operated inferior oblique muscles. They noted that fundus excyclotorsion was more common in eyes that had a double-bellied inferior oblique muscle, and postulated that the double-belly of the

Fig. 27.7. Inferior oblique traction testing may be inadequate to detect residual, uncut fibers of the inferior oblique muscle

Tenon’s capsule rather than into the sclera. These variations in the anatomy of the superior oblique tendon are important to recognize intraoperatively as they may have significant impact on surgical decisions.

27.9.3 Bifid Rectus Muscles

Bifid rectus muscle insertions have been reported in patients with craniofacial syndromes [32] and in otherwise healthy patients [33]. Sundaram and coworkers [33] reported a bifid medial rectus muscle insertion associated with intermittent distance exotropia in an otherwise healthy patient. Minor, intuitive modifications of the surgical plan are required to manage the bifid rectus muscle insertions. Our approach has been to suture the bifid components of the insertion together and recess or resect the two insertions as a unit.

27.9.4 Abnormal Rectus Muscle Insertions

Rosenbaum and Jampolsky [34] reported pseudoparalysis caused by an abnormal insertion of superior rectus muscle, which was inserted just above the insertion of the lateral rectus muscle. Okano and co-workers [35] reported on the treatment

of a patient with severe exotropia and a preoperative diagnosis of adduction paralysis who was found to have an anomalous posterior insertion of a hypoplastic medial rectus muscle 11.5 mm from the limbus. The patient was satisfactorily treated with a Hummelsheim transposition procedure, though it is unclear why the authors did not simply advance the medial rectus muscle. Wine and co-workers [36] operated on a 5-year-old boy with congenital left hemiparesis associated with schizencephaly and a large V-pattern exotropia, who was found to have lateral rectus muscles that were abnormally inferiorly positioned. Despite recession with supraplacement, the V-pattern exotropia persisted postoperatively, though there was also untreated overaction of the inferior oblique muscles, which may have contributed to the problem.

27.10 Accessory Muscle

In vertebrates, the retractor bulbi muscle is derived from the same embryonal tissue as other extraocular muscles. Several authors have reported the persistence of muscles in humans that were thought to be a vestige of the retractor bulbi muscle. Accessory extraocular muscles are uncommon, but when present they can produce bizarre and atypical strabismus. Anomalous orbital structures can produce a variety of unusual strabismus patterns [37]. Muhlendyck [38] has suggested that

persistence of the retractor bulbi muscle might be a cause of some cases that are clinically diagnosed as Duane syndrome. Kirkham [39] reported an accessory inferior oblique muscle.

Three major types of anomalous structures have been described: (1) those arising from the extraocular muscles themselves and inserting in abnormal locations, (2) fibrous bands that are located beneath the rectus muscles, and (3) discrete anomalous muscles originating from the posterior orbit and inserted in abnormal locations on the globe [37]. Clinical findings that may suggest the presence of an anomalous orbital structure include globe retraction, large vertical strabismus, and an elevation deficit that is worse in abduction [37]. Neuroimaging studies can be useful in identifying abnormal accessory extraocular muscles in the orbit (>Fig. 27.9).

Surgical treatment depends upon signs and symptoms as well as the nature of the particular abnormal orbital structure. Park and Ou [40] reported a patient diagnosed with a congenital third nerve palsy who was found to have an accessory lateral rectus muscle medial and parallel to the normal lateral rectus muscle that produced restriction to forced duction testing in adduction. Recession of the accessory muscle combined with a recess/resect operation of the normal medial and lateral rectus muscles resulted in resolution of the restrictive forces with a good surgical outcome. Surgical treatment of accessory extraocular muscles is not always required. Valmaggia and coworkers [41] reported finding a supernumerary intraconal muscle in the posterior aspect of the left globe of a child with marked elevation deficiency of the involved eye (>Fig. 27.10). The clinical and radiographic features of this child suggested the persistence of an atavistic structure, the retractor bulbi muscle. Treatment was not recommended because the patient

Chapter 27

was asymptomatic. Restrictive bands are sometimes found under the inferior rectus muscle in patients with congenital fibrosis syndromes.

27.11 Atypical Restrictive Strabismus

27.11.1 Thyroid-Related Ophthalmopathy

Enlargement of extraocular muscles can occur from a variety of processes including neoplasm, infections, inflammation, infiltrative disorders, and obstruction of orbital venous outflow. Thyroid ophthalmopathy is the most common cause of enlarged extraocular muscles in the adult population.

27.11.1.1 Oblique Muscle Involvement

Extraocular muscle fibrosis and contracture occur in a relatively predictable pattern in most patients with thyroid-related ophthalmopathy. Generally, only the rectus muscles are clinically involved. The order of most to least likely rectus muscle to be involved is the inferior, medial, superior, and lateral rectus muscle, respectively. Oblique muscle involvement is less commonly recognized, but may occur. Thacker and coworkers [42] reported four patients with thyroid-related ophthalmopathy who presented with incomitant vertical strabismus, A-pattern horizontal strabismus, over depression in adduction, and under elevation in adduction. Each of the patients also had significant incyclotorsion. Clear evidence of superior oblique enlargement was noted on orbital imaging of each patient. Intraoperative traction testing revealed relative tightness of the superior oblique muscle/tendon in all patients. The patients were treated with superior oblique tenotomy or superior oblique tendon silicone spacer procedures. A 6-0 Prolene tendon retrieval suture (aka chicken suture) was placed in the end of the transected tendon to allow for recovery and reversal of the tenotomy, if required postoperatively. Additional surgical procedures were performed on the rectus muscles with adjustable sutures as needed. The ocular motility disturbance was dramatically reduced in three of the four patients.

Fig. 27.9. Abnormal accessory muscle noted on neuroimaging of the orbit. {Reprinted from Valmaggia C, Zaunbauer W, Gottlob I (1996) Elevation deficit caused by accessory extraocular muscle. Am J Oph­ thalmol 121:444–445, copyright 1996, with permission from Elsevier [41]}

Fig. 27.10. Limited up gaze in a child with an accessory extraocular muscle. {Reprinted from Valmaggia C, Zaunbauer W, Gottlob I (1996) Elevation deficit caused by accessory extraocular muscle. Am J Oph­ thalmol 121:444–445, copyright 1996, with permission from Elsevier [41]}