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

Both vertical rectus muscle involvement and involvement of the superior oblique muscle can lead to development of vertical strabismus. In contrast to vertical strabismus caused by vertical rectus muscle restriction which is typically relatively comitant across the horizontal gaze fields, Thacker and coworkers [42] reported that the restriction due to involvement of the superior oblique muscle tended to be markedly incomitant across the horizontal gaze fields. Failure to recognize involvement of the superior oblique muscle and operating only on the vertical rectus muscles could exacerbate the horizontal and vertical incomitance, and could worsen the A-pattern as well as increase the incyclotorsion [42].

27.11.2 Superior Rectus Muscle Involvement

While the superior rectus muscle is often involved in patients with thyroid-related ophthalmopathy, involvement of the inferior rectus muscles is usually more severe and the presence of a hypotropia with limited up gaze usually predominates the clinical presentation. Simultaneous involvement of the superior rectus muscles and superior oblique muscles can produce very unusual strabismus in patients with thyroid-related ophthalmopathy. We treated a patient with thyroid-related ophthalmopathy who had severe restrictive strabismus includ-

ing a large angle esotropia, moderate angle left hypotropia, and incyclotorsion of 10° in the right eye and 12° in the left eye (>Fig. 27.11). The patient had previously undergone a 10-mm right medial rectus muscle recession prior to our evaluation. Orbital imaging revealed enlargement of all four rectus muscles in each eye and enlargement of the superior oblique muscle in both eyes (>Fig. 27.12). Forced traction testing was not done in the office preoperatively, and preoperative planning was based on the assumption that the left hypotropia was primarily due to asymmetric contracture of the left inferior rectus muscle relative to the right inferior rectus muscle and the incyclotorsion was thought to be due to involvement of the superior oblique muscles. The preoperative surgical plan was to perform asymmetric recession of the inferior rectus muscles and the left medial rectus muscle with adjustable sutures combined with tenotomy of the superior oblique tendon in both eyes.

At surgery, the overwhelming finding on forced duction testing was severe contracture of the superior rectus muscles, particularly the right superior rectus muscle. Thus, it became immediately obvious that the preoperative plan was incorrect and that the left hypotropia was present because the patient preferred to fixate with the right eye, which had a more severely restricted superior rectus muscle. The down gaze innervation required to overcome the severely contracted right superior rectus muscle resulted in the development of the left hypotropia due to Hering’s law of equal innervation.

Fig. 27.12. Orbital CT scan of the patient in Fig. 27.11

When an ocular deviation is due to restriction of the fixing eye, the primary consideration at surgery should be to free the restrictive forces in the fixing eye to make fixation and alignment in the primary position possible. Surgical decisions are guided by forced traction testing before and/or during surgery. In this case, the superior rectus muscle was recessed in both eyes, with a larger recession performed on the right superior rectus muscle. Nasal transposition of both superior rectus muscles was performed to help offset the large incyclotorsion. Evaluation of the fundus intraoperatively with indirect ophthalmoscopy revealed significant residual incyclotorsion. The right superior oblique tendon was noted to be extremely tight and a tenotomy was performed to help address the residual incyclotorsion. The left superior oblique tendon was moderately tight, and was left intact. A left medial rectus muscle recession with an adjustable suture was performed to treat the esotropia. Following postoperative adjustment, the incyclotorsion and esotropia were eliminated. He was able to overcome a small residual vertical deviation and achieve single vision by adopting a 20º right face turn. Because the patient was satisfied, no further treatment was recommended. This case emphasizes the importance of preoperative and intraoperative traction testing as well as the potential value of intraoperative examination of the fundus with indirect ophthalmoscopy for objective improvement in cyclotorsion in unusual cases.

A hypertropia and superior rectus muscle restriction in patients with thyroid-related ophthalmopathy can be so severe as to greatly impede or completely preclude the ability to surgically approach the muscle using standard techniques. Not only is the insertion of the superior rectus muscle further from the limbus compared to the other rectus muscles, but also the orbital rim and upper eyelid both limit surgical access to a severely restricted superior rectus muscle. Ing [43] reported the use of an upper lid splitting technique to allow better exposure of a severely contracted superior rectus muscle (> Fig. 27.13). While this may seem an extraordinary step for a strabismus surgeon to take in approaching an extraocular muscle, the risk

Chapter 27

Fig. 27.13. Upper eyelid splitting procedure to allow surgical access to a severely restricted superior rectus muscle. {Reprinted from Ing E (2005) Vertical upper-lid split incision for access to a severely restricted superior rectus muscle in a patient with Graves ophthalmopathy. J AAPOS 9:394–395, copyright 2005, with permission from the AAPOS [43]}

of complications when operating on an extremely contracted superior rectus muscle when exposure is poor can be significant enough to justify such an approach.

27.11.2.1Exotropia in Thyroid-Related Ophthalmopathy

Exotropia is extremely uncommon in patients with thyroidrelated ophthalmopathy. It is uncommon for several reasons:

(1)significant lateral rectus muscle contracture is infrequent,

(2)medial rectus muscle contracture is very common, and (3) contracture of the vertical rectus muscles, which have adduction as a tertiary function, is common. Each of these factors makes development of an exotropia unusual, except in the rare setting in which the lateral rectus muscle is asymmetrically involved relative to its antagonist, the medial rectus muscle, a condition which should be easily detected on orbital imaging. The presence of an exotropia in a patient with thyroid-related ophthalmopathy should trigger consideration of concurrent myasthenia gravis [44], a condition known to occur in a small proportion of patients with thyroid-related ophthalmopathy

27.12Strabismus Following Scleral Buckling Surgery

Strabismus following scleral buckling surgery for nal detachments is usually temporary [46]. Causes rary diplopia include periocular edema, muscle and edema, and reduced vision precluding fusion diplopia may be seen in as many as 5%–25% of cording to a review performed by Seaber and Strabismus occurring following scleral buckling

generally been attributed to scarring [48]. However, the condition is probably heterogeneous (>Table 27.1). High-resolution magnetic resonance imaging has revealed multiple other potential mechanisms [7], including occult rectus muscle disinsertion, restrictive interference by the explant, interference by a myopic staphlyoma, and anterior migration and transaction of a rectus muscle by an encircling explant. Fat adherence [37] and anesthetic myotoxicity related to retrobulbar injection [49] have also been reported as a possible cause of restrictive strabismus following scleral buckling surgery.

There have been numerous reports of unintentional rectus muscle detachment following scleral buckling procedures [50–52]. This can occur as a direct complication of surgery or can be caused by anterior migration of an encircling element that detaches the muscle postoperatively. The detached muscle may retract into the posterior orbit or reattach to the globe posterior to the buckle. The patient in Fig. 27.14 presented with a right hypertropia as a result of anterior migration of a silicone encircling element with detachment of the inferior rectus muscle in her nonamblyopic eye. She did well following retrieval and reattachment of the inferior rectus muscle, which had retracted into the posterior orbit. The muscle was identified because of its intact attachments to the lower eyelid retractors in the inferior oblique muscle. Though not necessary for this patient due to the obvious nature of the problem, highresolution orbital imaging can be helpful in clarifying the diagnosis and in helping to devise an appropriate surgical plan.

Fig. 27.14. Anterior migration of an encircling band placed to treat a retinal detachment has resulted in erosion of the inferior rectus muscle­ insertion

Scarring and adhesions Rectus muscles disinsertion

Restrictive interference by explant

Limitation of movement by a myopic staphlyoma Anterior migration and transaction of a rectus muscle Anesthetic myotoxicity related to retrobulbar injection

series by Cooper and coworkers [54] excyclotorsion was seven times more likely to occur than intorsion. Excyclotorsion was most commonly caused by partial or total disinsertion of the superior oblique tendon and tightening of the inferior rectus muscle related to the underlying scleral buckle. Intorsion occurred due to scarring of the superior oblique tendon to the nasal border of the insertion of the superior rectus muscle. Surgery was successful in reducing torsion 4° or more in almost 60% of their patients. The surgical plan was devised on a case-by-case basis and included standard recess/resect surgery of the rectus muscles, Harada–Ito procedures, inferior oblique recessions, adjustable sutures, and dissection of the scar tissue. No formula is available to manage such complex patients.

For patients who require treatment of strabismus following scleral buckling surgery, reasonable treatment options may include standard strabismus surgery, botulinum toxin injection, and/or prism therapy [53]. The success of treatment using botulinum toxin has been conflicting [55, 56]. The majority of patients can achieve single binocular vision in the primary position with treatment [57]. The prognosis for restoring binocular vision is lower in patients who have had a macula-off retinal detachment, poor visual acuity, image distortion, and/or a history of multiple procedures for retinal detachment [53]. Some surgeons have recommended removal of the scleral buckle and other explants as the first step in the management of strabismus associated with scleral buckling surgery [58]. We have rarely found removal of encircling buckles to be of value in the treatment of strabismus following retinal detachment repair, and rarely recommend this as a first step. Hydrogel implants (see below) and larger radial elements impeding ocular ductions, however, usually require removal. Consultation with a retina surgeon may be appropriate in these cases to determine the risk of recurrent retinal detachment if removal of these explants is to be considered.

While strabismus surgery performed on the eye that has not undergone a scleral buckling procedure is technically easier and may be associated with a greater likelihood of restoring single vision [58], patients with a history of unilateral retinal detachment are often, if not usually, reticent about having strabismus surgery performed on their sound eye. Thus, in most cases, we perform strabismus surgery on the eye that has undergone previous scleral buckling surgery because of strong

patient preference. If surgery is performed on the sound eye in a patient with a relatively small deviation and without significant restriction of ocular ductions in the contralateral eye, surgical planning and the technical aspects of surgery are relatively straightforward.

Strabismus surgery on an eye that has undergone previous scleral buckling surgery, on the other hand, can be challenging. In general, more surgery is often required than would initially be suspected for the size of a given deviation. Surgery can be unpredictable, and therefore adjustable sutures may be considered when feasible. We generally attempt to correct strabismus without removal of the scleral buckle. Two technical problems commonly arise during surgery on an eye that has an intact scleral buckle. The first involves isolation and dissection of the target rectus muscle. Generally, the muscle can only be hooked posterior to the scleral buckle, because the muscle anterior to this point is usually tightly adherent to the capsule surrounding the explant. Careful dissection of the anterior aspect of the muscle from the underlying encapsulated scleral buckle can

usually be accomplished and the muscle can then usually be disinserted from the globe at its anatomical insertion. A standard recession can then be performed.

Reattachment of the recessed muscle posterior to the scleral buckle is usually straightforward and relatively simple, provided good exposure of the surgical site is possible. Occasionally, a recessed muscle needs to be placed on the sclera in the area underlying or near the scleral buckle. The muscle should not be placed under the buckle, because the buckle will produce a posterior fixation suture effect limiting ocular ductions and the buckle may erode through the newly recessed muscle postoperatively. We prefer to suture the recessed muscle directly to the sclera and will often remove a small segment of the scleral buckle posteriorly, leaving the anterior portion of the scleral buckle intact. The muscle can then be sutured directly to the sclera (>Fig. 27.15). Occasionally we have found it necessary to suture rectus muscles directly to the scleral buckle and its surrounding capsule. This technique has worked well, but we are always concerned about long-term stability of the muscle

Fig. 27.15a–c. Removal of the posterior portion of a scleral buckle to allow the rectus muscle to be sutured to the sclera under the buckle. a Buckle exposed after detachment of rectus muscle, b posterior seg-

ment of buckle removed and discarded, and c muscle sutured directly to the sclera in the area previously under the buckle

insertion when the muscle has been sutured to the scleral buckle and its capsule, and we try to avoid this technique when possible.

It is sometimes impossible to cleanly dissect the anterior portion of a rectus muscle away from the capsule surrounding the scleral buckle. When this occurs, the rectus muscle can be transected at its junction with the posterior edge of the scleral buckle. The now shortened rectus muscle can then be recessed or resected as desired (>Fig. 27.16). Adjustable sutures can be helpful since the effect of surgery may be unpredictable; although while they are useful, adjustable sutures are often so technically challenging in this setting that this limits their use.

The treatment of restrictive strabismus is usually limited to recession surgery alone. This may not be the case in many patients with scleral buckle-related strabismus, where restrictive forces tend to be relatively mild and resection of a rectus muscle is often required to achieve the desired effect, particularly if the patient is unwilling to have surgery performed on the sound eye. Reattaching a resected rectus muscle to the sclera may require placement of sutures slightly anterior to the scleral buckle in order to facilitate reattachment of the muscle to the globe.

Patients with scleral buckle-related strabismus should understand that the prognosis for successful treatment is often guarded, depending on the complexity of the problem. Successful surgery may allow the patient to achieve single vision in the primary position, but the field of single vision may be small in some patients.

27.13 Hydrogel Explants

Treatment of strabismus caused by hydrogel explants deserves special consideration. These explants are no longer used in scleral buckling surgery. Patients who have received hydrogel explants in the past may present with strabismus, pain, a feeling of orbital fullness, and a subconjunctival mass [59]. Hydrogel explants can enlarge dramatically over time and onset of symptoms may not occur until years after buckling surgery. The strabismus produced is restrictive in nature and may be worse in the mornings when the hydrogel implant has become hydrated during the patient’s dependent sleep position. Surgical correction of associated strabismus requires removal of the hydrogel explant. Removal of these explants is technically challenging. The hydrogel material is very fragile and fragments when surgically manipulated. It usually must be removed in piecemeal fashion. In a study involving 17 eyes of 15 patients, Kearney and coworkers [59] reported relief of pain and discomfort with improvement of ocular motility in all patients following removal of their hydrogel explants. Extraocular muscle surgery was not required in any of their patients following removal of the explant. Hydrogel sponges can slowly erode through the sclera and therefore consultation with a retinal surgeon is important when considering removal of a hydrogel explant. In the series reported by Kearney and coworkers [59], three eyes suffered intraoperative eye wall perforation, one developed bacterial endophthalmitis postoperatively, and five eyes developed recurrent retinal detachments.

Fig. 27.17. Computed tomography scan of the orbit in a patient presenting with a small left hypotropia and a small esotropia. The presence of subtle enophthalmos prompted a scan to be ordered, revealing an old medial wall blowout fracture with entrapment of the medial rectus muscle

27.14 Occult Orbital Fractures

Unsuspected occult blowout fractures can produce complex strabismus. A history of prior trauma may not be reported or even recalled by the patient. The surgeon must maintain a high index of suspicion and should consider orbital imaging of patients with atypical strabismus [60]. Strabismus associated with occult posterior orbital wall fractures is usually associated with at least mild restriction of ocular motility and is often, if not usually, associated with enophthalmos, which can be subtle. The patient in Fig. 27.17 presented with an atypical and unexplained small, but symptomatic, vertical and horizontal deviation. Careful examination of the left eye revealed mild enophthalmos. Computed tomography scanning of the orbits revealed an occult medial wall fracture with entrapment of the medial rectus muscle posteriorly. Though he did not recall a history of ocular trauma during our initial evaluation, he recalled suffering a significant bruise to his left eye during a boxing match 20 years beforehand, after we informed him of the presence of the fracture. The patient was sent to an oculoplastics specialist for repair of the fracture. In this case the diplopia resolved and strabismus surgery was not required. In many cases, strabismus will persist following fracture repair, though the deviation is often significantly altered by fracture repair.

27.15Strabismus Associated with Glaucoma Setons

Strabismus has been reported as a result of mechanical restriction caused by a variety of glaucoma drainage devices [61–67]. Proposed mechanisms for glaucoma implant-related strabismus (>Table 27.2) include an increase in the length–tension curve of the muscle induced by the underlying bleb, a posterior

Increase in the muscle length–tension curve induced by underlying bleb

Posterior fixation effect

Bulk associated with the implant and its capsule Orbital–implant disproportion

ciated with the implant and its capsule, and orbital–implant disproportion [63, 65, 66]. The Baerveldt 350-mm2 glaucoma implant may be particularly prone to inducing heterotropia and ocular motility restriction [62]. The condition is best managed by removal or repositioning of the orbital glaucoma drainage device or removal of a large associated cyst, if present. The patient in Fig. 27.18 presented with vertical and horizontal diplopia following placement of an Ahmed valve in the superonasal orbit [66]. The patient would not allow surgery on her sound eye and would not allow the drainage device to be removed or moved. We were able to effectively counteract her strabismus by performing a resection and transposition of the superior rectus muscle, resulting in realignment of her eyes in the primary position with restoration of single vision in the primary position.

Unless the drainage device is to be removed, the strabismus surgeon should avoid the area of active filtration. If the sound eye cannot be operated, this may mean devising a specific approach that will stay clear of the region such as resecting the inferior rectus for the treatment of a hypertropia, a condition that would normally be corrected through recession of the superior rectus muscle. No formula is available for treatment of glaucoma seton-related strabismus and each case must be managed with a uniquely designed surgical plan.

27.16 High Myopia Related Strabismus

Atypical strabismus has been reported in patients with high myopia. Demer and von Noorden [68] reported restriction of eye movements due to contact between the posterior aspect of an elongated globe and the posterior orbital walls. In other cases, the cause of atypical strabismus in patients with high myopia has historically been less clear. Adult patients with high axial myopia may develop a progressive restrictive esotropia and hypotropia. The condition has been referred to as the “heavy eye syndrome.” Though moderate success has been reported with standard strabismus surgery [69] the condition generally does not respond adequately to standard recession and recession techniques. Several theories have been advanced to explain the cause of this unusual ocular motility disturbance in patients with high axial myopia . Theories proposed include structural abnormalities of the extraocular muscles [70], sixth nerve palsy, and myopathic paralysis of the lateral rectus muscle by compression of the muscle against the orbital rim by the enlarged globe [71]. Krzizok coworkers [72] evaluated a large

Fig. 27.18. Strabismus caused by mechanical restriction related to an Ahmed valve in the superonasal orbit

group of patients with this condition using magnetic resonance imaging. They demonstrated that the lateral rectus muscle was downwardly displaced in the mid orbit by a median of 3.4 mm (>Fig 27.19). Furthermore, they demonstrated that normalization of the lateral rectus muscle with a silicone loop (“guide pulley”) or a nonabsorbable suture resulted in good alignment with improvement of abduction and elevation [73].

Tsuranu and coworkers [74] and Nishida and coworkers [75] also reported on restrictive strabismus in patients with high myopia, noting that there was more significant disruption of the orbit in many cases than isolated inferior displacement of the lateral rectus muscle. They demonstrated that the posterior aspect of the globe became subluxated superiorly and temporally resulting in deviation of the anterior aspect of the globe medially and inferiorly. The patient in Fig. 15.7b, c demonstrates these findings. In addition to normalization of the paths of the lateral rectus muscle, we have utilized partial transposition of the superior and lateral rectus muscle bellies toward the superotemporal aspect of the orbit, securing the adjacent muscle bellies together as far posteriorly as possible using nonabsorbable suture as described in Chap. 15. The muscles are not disinserted during this transposition procedure, which resembles a Jensen transposition.

27.17 Brown Syndrome

Acquired Brown Syndrome is usually unilateral and is not common. It has been associated with a number of conditions

Fig. 27.19. Magnetic resonance imaging of the orbit of a patient with high myopia with esotropia and hypotropia, demonstrating disturbance of the paths of each of the rectus muscles, and displacement of the posterior globe up and out. {Reprinted with permission from Krzizok TH, Kaufmann H, Traupe H (1997) New approach in strabismus surgery in high myopia. Br J Ophthalmol 81:625–630, copyright 2007 [73]}

including rheumatoid arthritis, pseudotumor, sinusitis or sinus surgery, orbital abscess, endophthalmitis, orbital trauma, and metastatic disease, or it may be idiopathic. Rao and coworkers [76] reported a case of acquired Brown syndrome due to Cys­ ticercus cellulosae, a parasitic cyst. If an inflammatory etiology is suspected, injection of steroids adjacent to the trochlea can be an effective treatment, often resulting in resolution of symptoms within a few days. Orbital imaging studies can be helpful in both identifying the etiology and developing a surgical plan in noninflammatory cases.

Fig. 27.20. Use of a scalpel to detach a tight rectus muscle. The scalpel is used to gently cut through the insertion while the hook protects the underlying sclera

27.18 Congenital Extraocular Muscle Fibrosis

Congenital fibrosis of extraocular muscles most commonly involves the inferior rectus muscles and/or medial rectus muscles, in our experience. Patients with congenital fibrosis involving the inferior rectus muscles may present with a severe hypotropia, chin-up head posture, and true ptosis or pseudoptosis. We have noted anomalous contracture of the medial rectus muscles in attempted up gaze in patients with bilateral congenital fibrosis involving the inferior rectus muscles. Up gaze limitation combined with contraction of the medial rectus muscles on attempted up gaze superficially resembles Perinaud syndrome, and these patients have often undergone neuroimaging prior to evaluation by us because of this concern. The distinguishing ophthalmologic feature is absence of globe retraction with attempted up gaze as occurs in Perinaud syndrome. The diagnosis of congenital fibrosis syndrome is often suspected in the first months of life, but the diagnoses may be difficult to confirm until the child is older, due to examination difficulties in an uncooperative child.

Surgical correction requires recession of the fibrotic muscle(s). Free tenotomy may be required in severe cases. Disinsertion of a severely restricted muscle from the sclera can be hazardous and can result in laceration of the sclera. The use of a sharp blade to gradually transect the muscle by slowly cutting down through the muscle to the underlying muscle hook can reduce the risk of injuring the sclera (>Fig. 27.20).

27.19 Miscellaneous Muscle Abnormalities

Acquired strabismus has occasionally been reported due to focal metastasis of a malignancy [77] and can also result from local benign and malignant neoplasia (>Fig. 27.21). Careful history and ophthalmologic examination and a strong index of suspicion in patients with atypical strabismus are required to diagnose these unusual situations.

Extraocular muscle involvement has been reported with idiopathic primary systemic amyloidosis [78, 79]. Sharma and coworkers [80] reported a patient with strabismus fixus and severe convergence due to amyloidosis causing paralysis of the lateral rectus muscles. Bilateral horizontal recession/resection surgery resulted in significant improvement. We managed a patient with no history of amyloidosis who had a long history of esotropia and mild abduction deficit in the left eye. Historically the esotropia had been of sudden onset and had been stable for many years. A recess/resect operation on the left eye was planned to treat a presumed residual microvascular sixth nerve palsy. At surgery, a white/yellow material was noted to be adherent at the lateral rectus muscle. Concerned that the material might represent a neoplastic or infectious process, strabismus surgery was not performed. Instead, a biopsy of the lesion was made and histopathologic studies demonstrated amyloidosis.

27.20 Abnormalities of the Sclera

27.20.1 Thin Sclera

Areas of scleral thinning or scleral ectasia can present significant challenges when attempting to reattach a muscle to the sclera. When thin sclera is encountered, sutures can be placed in adjacent thicker sclera using a hang-back approach (Chap. 9). Alternatively, techniques that do not require placement of sutures into the sclera can be helpful [81, 82]. We developed a technique that allows rectus muscle recession or resection without the need to place sutures in the sclera. Muscle insertion sutures are used in place of scleral sutures and the muscle sutures are then tied to the insertion sutures to perform both a recession and a resection. This technique is reviewed in Chap. 21. Tissue adhesives have also been suggested for reattachment of a muscle to the sclera, but are not yet practical enough for common use.

Scleral plaques often develop as a focal translucency of the sclera in elderly individuals [83]. The lesions are most often located anterior to the tendon insertion of the horizontal rectus muscles. With age, the plaques can become significantly calcified and contain a large amount of calcium sulfate. Attempting to pass suture needles through this material can be extremely hazardous. Instead, sutures should be passed through adjacent healthy sclera, utilizing a hang-back approach to accomplish the desired surgical result. The final resting position of the muscle should not overlie a scleral plaque, as it is unclear if the muscle will adhere to the plaque sufficiently to secure the muscle to the sclera.

Fig. 27.21. Patient with pseudo-Brown syndrome due to a benign tumor involving the inferior rectus muscle

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59.Kearney JJ, Lahey JM, Borirakchanyavat S et al (2004) Complications of hydrogel explants used in scleral buckling surgery. Am J Ophthalmol 137:96–100

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Chapter 27

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