|INCOMITANT STRABISMUS UPDATE
|Year : 2015 | Volume
| Issue : 3 | Page : 271-278
Complications of strabismus surgery
Scott E Olitsky1, David K Coats2
1 Children's Mercy Hospital; Department of Ophthalmology, University of Missouri, Kansas City School of Medicine; Department of Ophthalmology, University of Kansas School of Medicine, Kansas City, USA
2 Texas Children's Hospital, Texas; Baylor College of Medicine, Houston, USA
|Date of Web Publication||1-Jul-2015|
Scott E Olitsky
3101 Broadway Blvd, Kansas City, MO 64111
Source of Support: None, Conflict of Interest: None
| Abstract|| |
All surgeries carry risks of complications, and there is no way to avoid ever having a complication. Strabismus surgery is no different in this regard. There are methods to reduce the risk of a complication during or after surgery, and these steps should always be taken. When a complication occurs, it is important to first recognize it and then manage it appropriately to allow for the best outcome possible. This article will discuss some of the more common and/or most devastating complications that can occur during or after strabismus surgery as well as thoughts on how to avoid them and manage them should they happen.
Keywords: Complications, Strabismus, Surgery
|How to cite this article:|
Olitsky SE, Coats DK. Complications of strabismus surgery. Middle East Afr J Ophthalmol 2015;22:271-8
| Introduction|| |
It is said that the only surgeons who do not have complications are those who do not operate and those that lie about having no complications. All surgeries carry risks of complications, and there is no way to avoid ever having one. Strabismus surgery is no different in this regard. There are methods to reduce the risk of a complication during or after surgery, and these steps should always be taken. When a complication occurs, it is important to first recognize it and then manage it appropriately to allow for the best outcome possible. This article will discuss some of the more common and/or most devastating complications that can occur during or after strabismus surgery as well as thoughts on how to avoid them and manage them should they happen.
| Anterior Segment Complications|| |
Dellen are characterized as shallow, clearly defined excavations at the margin of the cornea. They are generally 1.5-2 mm in diameter and occur following localized evaporation and dehydration of the cornea. Resulting disruption of the tear film and localized evaporation result in increasing compactness of the corneal stromal lamellae.
When dellen occur following strabismus surgery, they typically develop within the first 2 weeks and tend to occur more frequently on patients operated with a limbal approach compared to those operated using a nonlimbal approach. , Dellen probably often go undiagnosed because subjective symptoms may be absent, clinical findings may be subtle, and strabismus surgery is often performed on small children who cannot be readily examined at a slit lamp. The occurrence of dellen is much more common following resection procedures compared to recession procedures and are much more likely to occur following very large resections. Their formation following horizontal rectus muscle surgery is not uncommon, but it is very rare to see after vertical rectus muscle or oblique muscle surgery.
Treatment of dellen involves corneal rehydration and measures to reduce limbal conjunctival elevation. A lubricating ophthalmic ointment usually leads to resolution within a few days to a week, accompanied by spontaneous reduction in bulbar conjunctival swelling as postoperative healing progresses. Patients with an underlying tear film deficiency may be at higher risk and require closer follow-up.
| Inadvertent Advancement of the Plica Semilunaris Conjunctivae|| |
Inadvertent advancement plica semilunaris conjunctivae (often simply referred to as plica) typically results from the suturing of plica to the conjunctiva adjacent to the limbus. This complication may occur following strabismus surgery using a limbal incision. During standard limbal surgery, the anterior aspect of the limbal conjunctival flap becomes folded beneath the plica. At the conclusion of the surgery, the surgeon attempts to identify the anterior edges of the conjunctival flap. The plica may have become hydrated and swollen during surgery and the surgeon mistakenly believes that he/she has grasped the anterior corners of the conjunctival flap, when in fact the edges of the plica have been inadvertently grasped. [Figure 1] demonstrates how easily this can occur. Only by careful study of the anatomy will the surgeon recognize that the medial angle of the eye appears abnormal and that the swollen plica has been inadvertently advanced forward. Once the mistake is recognized, key landmarks can be easily identified.
|Figure 1: (a) Inadvertent advancement of the plica semilunaris during closure of a limbal incision: (a) Appearance of the medial angle of the conjunctiva when the plica is held against the limbus, demonstrating how the surgeon can be fooled into believing that the edge of the conjunctival flap has been identified, and (b) appearance of the same eye after release of the plica and acquisition of the edges of the conjunctival flap (with permission from Coats DK, Olitsky SE, Strabismus surgery and its complications, Springer 2007)|
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This complication may be more likely following prolonged surgery and is most prone to occur after an extensive reoperation and in older patients with extremely thin conjunctiva. The use of excessive hydration during surgery may result in greater distortion of the anatomy by increasing edema of tissues in the operative site.
Prevention of inadvertent advancement of the plica should begin before surgery is initiated. The surgeon should examine the anatomy of the medial aspect of the eye and take care to restore the anatomy to its preoperative state at the time of closure. In cases where a difficult closure is anticipated a sterile methylene blue skin marking pen can be used to mark the anterior corners of the conjunctival flap before proceeding with surgery. At the conclusion of the case, these corner markers are easy to locate, and they help facilitate accurate conjunctival closure.
| Chemosis|| |
Chemosis occurs to a mild degree in all patients undergoing strabismus surgery, but can occasionally be pronounced. Severe chemosis is rarely seen following routine strabismus surgery but can disrupt the suspensory attachments to the conjunctival fornix through hydraulic dissection. Prolonged prolapse of the conjunctiva may result in fusion of the folds together requiring excision.  Treatment is initially supportive, consisting of aggressive lubricating ophthalmologic ointments, with the addition of cellophane tents at night if the swollen conjunctiva protrudes anterior to the eyelids. Topical steroids are often prescribed and appear to be of value. This conservative treatment regimen will usually result in significant improvement or resolution within a few days to a week.
Pyogenic granulomas appear as a fleshy red mass with relatively rapid growth. The lesion is a proliferative fibrovascular response to previous trauma including surgery. In most cases, these lesions will resolve spontaneously. Many surgeons recommend the use of topical steroids although their efficacy has not been proven. Surgical excision may be required for pyogenic granulomas that fail to resolve after topical treatment alone. Reoccurrence following excision is rare.
Extruded/exposed Tenon's fascia
Occasionally extrusion/exposure of Tenon's fascia through the conjunctival incision occurs following strabismus surgery. This complication can be avoided by ensuring that the edges of the conjunctival incision are well opposed or sutured following surgery. If a large amount of Tenon's fascia is noted to be extruding through the conjunctival incision at the end of the case, the surgeon can either excise the extruding Tenon's fascia or place additional sutures in the conjunctiva to fully internalize the exposed fascia. Occasionally, however, a patient will present postoperatively with exposed Tenon's fascia, sometimes with the exposed Tenon's fascia stringing from the wound and even overhanging the eyelid. The exposed Tenon's fascia can be trimmed flush with the conjunctival surface. Topical steroids can be used in cases where excision is not possible, and resolution typically occurs within days or weeks.
Epithelial inclusion cyst
Subconjunctival epithelial inclusion cysts occur infrequently as a complication of strabismus surgery. They can occur anywhere in the operative field, but most commonly occur adjacent to conjunctival incisions or near the new muscle insertion into the sclera. These cysts are thought to arise from inclusion of conjunctival epithelial cells into the substantia propria or the sclera. Nests of conjunctival epithelial cells that have become deposited during strabismus surgery later proliferate, forming a central cavity and ultimately forming a visible cyst. If the conjunctiva becomes adherent to the suture and is pulled into the scleral tunnels, conjunctiva epithelial cells may become deposited in the scleral tunnels and allow a cyst to form [Figure 2].
|Figure 2: Dragging of the conjunctiva into the scleral suture tunnels which could implant epithelial cells into the scleral tracts and lead to epithelial cyst development (with permission from Coats DK, Olitsky SE, Strabismus surgery and its complications, Springer 2007)|
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When an epithelial inclusion cyst forms at the site of muscle reattachment to the sclera failure to recognize that the muscle is attached to the cyst can result in detachment of the muscle. While very small epithelial inclusion cysts can be effectively removed through a small conjunctival incision placed adjacent to the cyst, most medium to large epithelial inclusion cysts are best removed through a standard limbal conjunctival incision, similar to the limbal incisions created for surgery on the rectus muscles. Limbal incisions allow the surgeon to maintain control of adjacent muscles during excision. Isolation of the adjacent muscle on a muscle hook can help ensure the safe removal of the cyst without accidental disinsertion of the muscle if the cyst is large and located close to the muscle. The goal of surgery should be to remove epithelial inclusion cysts intact. Manipulating the cyst with forceps should be avoided as the cyst can easily be ruptured. Once the cyst has been fully exposed, it should be carefully excised from the underlying sclera. Attachment of the cyst to the underlying sclera is typically very firm and care must be taken to transect these fine but firm attachments to the underlying sclera without rupturing the cyst. If the cyst ruptures during removal, every attempt to excise all visible elements of the cyst should be made along with irrigation of the operative site in an attempt to wash away any stray epithelial cells, and applied cautery to the sclera where the cyst was attached. A nonsurgical option for the management of epithelial inclusion cysts is aspiration of cyst contents, intracyst injection of alcohol which is then left in the cyst for several minutes, and then aspiration of the alcohol.
| Anterior Segment Ischemia|| |
Anterior segment ischemia is a rare but potentially sight-threatening complication following strabismus surgery.  Risk factors for the development of anterior segment ischemia include advanced age, previous rectus muscle surgery and history of a vasculopathy, such as diabetes and/or hypertension. Of these risk factors, advanced age and the number of rectus muscles being operated upon appear to be the most important. Surgery on an adjacent vertical and horizontal rectus muscle is more likely to lead to an observable effect on anterior segment circulation. , Detachment of three or four rectus muscles at one time carries a significant risk of compromising the vascular supply of the anterior segment in some patients.
A history of prior extraocular muscle surgery should be taken into account when weighing the risk of anterior segment ischemia developing if further surgery is planned. A direct connection between the anterior ciliary arteries that are severed at the time of surgery is never reestablished. Therefore, surgery on other rectus muscles later in life increases the risk of developing anterior segment ischemia. This is especially true if further surgery involves detachment of the third or fourth rectus muscle in the same eye. Repeat surgery on a previously operated rectus muscles does not itself increase the risk of anterior segment ischemia since reestablishment of blood flow through the previously disrupted anterior ciliary artery does not occur.
Underlying vascular disease plays an important role in determining which patients are most at risk for anterior segment ischemia. Patients with co-existent vascular disease in combination with other aforementioned risk factors are considered at greatest risk for anterior segment ischemia. While strabismus surgery is not contraindicated, surgery must be planned carefully, and patients must be counseled appropriately.
Anterior segment ischemia can range from mild and self-limited to severe and vision threatening. Mild cases with reduced iris perfusion may be demonstrated only with iris angiography while more severe cases may include changes in pupil shape and reactivity, postoperative uveitis, cataract, keratopathy, hypotony and eventual loss of vision and even phthisis bulbi in rare cases.
Because the signs of anterior segment ischemia are similar to those seen in more typical uveitis, many ophthalmologists treat empirically with corticosteroids. Mild anterior segment ischemia is generally treated with topical agents, and more severe cases are often treated with oral corticosteroids. There are no data to suggest that any specific treatment of anterior segment ischemia improves the outcome of this disorder.
The best treatment for anterior segment ischemia is prevention. A surgical plan for at-risk patients should be designed that will minimize the risk that clinically significant anterior segment ischemia will develop. Potential strategies include limiting the number of rectus muscles that are detached from the globe, techniques to preserve anterior ciliary arteries and staging surgical procedures when needed. ,
| Scleral Perforation|| |
The reported incidence of scleral perforation varies widely. Retrospective studies and sur veys are likely to greatly underestimate the number of scleral perforations and deep passes that actually occur. One prospective study found the incidence of scleral perforation to be 5.1%. 
The risk of scleral perforation appears to be greatest during reattachment of a muscle to the sclera, where the needle must carefully penetrate the sclera, but only deep enough to secure the muscle to the globe. The margin of error may be very small in eyes with a thin sclera. Scleral perforation probably occurs more commonly during recession than during resection surgery.  This is presumably because exposure of the surgical site is more difficult with recession surgery.
Recognition of a perforation is necessary before potential treatment can be considered. Scleral perforation probably goes unrecognized in many cases. Intraoperative signs of a scleral perforation may vary depending on the patient and the severity of the perforation. The surgeon often "feels" that the needle pass was too deep and is immediately suspicious that a perforation may have occurred. Recognized scleral perforations are often heralded by a small piece of uvea or a bead of vitreous on the tip of the suture needle. Indirect ophthalmoscopy to inspect the retina underlying the surgical site should be performed when a scleral perforation is suspected. Most scleral perforations are small, even microscopic. Lacerations of the sclera and even unintentional block resections of the sclera can occur during strabismus surgery, and the surgeon must be prepared to manage this complication or have access to a consultant surgeon. If a large retinal tear is noted, or if a small retinal tear is noted in a patient at high risk for retinal detachment, laser retinopexy may be required and the patient should be followed closely during the postoperative period for evidence of endophthalmitis and/or retinal detachment. A child with well-formed vitreous is probably at low risk for detachment and laser may not be necessary.
Because the needles and sutures used during strabismus surgery are often contaminated during surgery, it may be good general practice when a perforation is suspected to withdraw the needle and suture and reposition it in an alternative location. , In addition, antibiotic drops and/or 5% povodine-iodine solution can be applied to the operative site. Some surgeons will administer subconjunctival antibiotics, a dose of intravenous antibiotics and/or prescribe prophylactic topical and/or oral antibiotics postoperatively. There is no scientific data to validate any specific protocol.
Probably the most important step to take after a scleral perforation has been identified is to inform and educate the patient and/or family so that they are aware of the potential for a serious complication and understand the signs and symptoms of endophthalmitis and retinal detachment in the rare event that one of these complications occurs and follow the patient carefully. Careful surgical planning and technique are both important in preventing scleral and eye wall perforation during strabismus surgery. Maintaining adequate surgical exposure and using proper needle passing techniques are important to reduce the risk of perforation. The surgeon should avoid the tendency to believe that scleral perforation only occurs during muscle reattachment to the globe, but instead should be vigilant throughout the procedure, because scleral perforation can occur at virtually any time of surgery. The use of a hang-back recession technique may be helpful as it allows excellent exposure regardless of the amount of recession being performed. Its use in patients believed to be at higher risk for scleral perforation should be specially considered.
| Postoperative Infection|| |
Serious infections following strabismus surgery are uncommon. Most busy strabismus surgeons are unlikely to see more than one or two cases of endophthalmitis and/or orbital cellulitis during their entire career. Other important, but less serious infections, such as preseptal cellulitis and subconjunctival abscesses, are more common. Endophthalmitis is so rare after strabismus surgery that it is often initially misdiagnosed. The visual outcome of endophthalmitis following strabismus surgery is usually poor, and this could in part be compounded by a delay in diagnosis. Thus, surgeon awareness of risk factors, clinical presentation, and treatment remain important.
The most common source of viable organisms producing endophthalmitis after strabismus surgery is not known. Potential sources of infection include the normal bacterial flora in the region of the operative site, contaminated surgical material, postoperative periocular abscess, and transient endogenous bacteremia. Most of the available data on risk factors for surgical site contamination and for risk of endophthalmitis following ophthalmologic surgery relate to cataract surgery and other intraocular surgical procedures. Though uncomplicated strabismus surgery does not result in perforation of the sclera, the strabismus surgeon should still be aware of these reports.
The surgeon's hands are an important potential source of bacterial contamination during surgery. Glove perforation during surgery occurs more frequently than surgeons may realize and glove perforation not only exposes the patient to contaminants on the surgeon's hands but also exposes the surgeon to potentially infected patient tissues and body fluids. Glove perforation often happens while handling suture needles. Sutures should be loaded onto the needle holder without ever touching the needle itself. Placement of a needle into a needle holder can be easily facilitated by holding the suture material close to the needle. Holding the needle in one's hand while placing it into the needle holder or passing it off the operative field is a common, but very poor, practice. It exposes both the patient and operating room personnel to unnecessary risk.
Instruments, implants, explants, and surgical supplies can become contaminated during any surgical procedure through several potential mechanisms. The ocular adnexa and conjunctiva of the patient are prime sources of potential contamination during ophthalmologic surgery. The rate of needle contamination during strabismus surgery has been demonstrated to be 15% in one study.  Given the fact that the sutures and needles used during surgery have a high potential to become contaminated with bacteria during routine strabismus surgery, steps to reduce the risk of exposure to contaminated needles and sutures should be considered. Isolation of the eyelids and lashes with an adhesive drape may reduce the potential for contamination during ophthalmic surgery though there is no evidence that this measure reduces the risk of infection related to strabismus surgery. If a scleral perforation is suspected or confirmed during surgery, the surgeon should consider halting passage of the needle and withdraw it immediately before potentially contaminated suture material is drawn through the perforation site. Likewise, if the needle has already been passed through the sclera, it may be prudent to cut the suture flush with the sclera and remove it, to avoid having to draw additional potentially contaminated needle and suture back through the suspected perforation site to remove it. Leaving a foreign body (suture) in a scleral perforation site has the potential to increase the risk of infection, and thus repositioning of the suture to another site should be considered.
The estimated incidence of endophthalmitis following strabismus surgery ranges from 1 in 350,000 cases suggested in 1962-1 in 18,500 cases suggested in 1992. , Numerous risk factors have been proposed. Scleral perforation is commonly believed to increase the risk of developing endophthalmitis following strabismus surgery though clear evidence that this is the case is not available.  The cause of endophthalmitis after strabismus surgery is not known and is probably variable. Several theories have been proposed including an endogenous origin, presence of partial obstruction of the nasolacrimal duct and upper airway infection. ,
The insidious presentation of endophthalmitis following strabismus surgery and the tendency for children not to complain of unilateral vision loss both make this already rare condition even more difficult to accurately diagnose. An accurate diagnosis of endophthalmitis is often not made until several days after the onset of signs and/or symptoms which may include pain, eyelid swelling, and redness. The onset of symptoms has been reported as early as 1 day after surgery to as long as 13 days after surgery. Thus, no reasonable follow-up schedule can ensure that the surgeon will be able to make an early diagnosis of endophthalmitis.
Most surgeons follow treatment guidelines as established by the endophthalmitis vitrectomy study when intraocular infection is suspected.  However, because most strabismus surgery is performed on children, assessment of vision in infants and young children may be impossible, making application of the endophthalmitis vitrectomy study recommendation difficult. In addition, translating these results to noncataract surgery-related cases of endophthalmitis may be controversial. It should be stressed that visual outcomes from endophthalmitis following strabismus surgery are often poor. Endophthalmitis after strabismus surgery is rare, and there is a complete absence of clinical trials to provide evidence-based science on how to manage patients with this complication.
Despite its infrequency, the poor visual outcome commonly associated with endophthalmitis after strabismus surgery justifies preventative measures. Prevention of all cases of endophthalmitis following strabismus surgery is not feasible. "Minor" preoperative infections, which are often considered unimportant by operating surgeons, might need to be reevaluated. The protective value of topical antibiotics following strabismus surgery is controversial, and no data exists to prove that their routine use serves any benefit in otherwise uncomplicated strabismus surgery. Given the typical delay in diagnosis, probably more important is for the strabismus surgeon to be aware of the potential signs and symptoms of endophthalmitis and review these signs and symptoms with patients and families after surgery and ensure that patients have ready access to the surgeon in the days and weeks immediately following surgery in the event that a problem develops.
Periocular infection (orbital and preseptal cellulitis)
Orbital and preseptal cellulitis has been reported infrequently following strabismus surgery. It is rare enough following strabismus surgery that it may not be initially suspected and treatment may be delayed. Early recognition and prompt treatment, including possible hospital admission for intravenous antibiotics, is important.
A subconjunctival abscess diagnosed following strabismus surgery should be surgically drained as soon as practical after it is recognized, and the patient started on antibiotics. Affected patients should undergo a dilated fundus examination and slit lamp examination to assess for intraocular infection and should be followed closely for development of endophthalmitis and/or orbital cellulitis. They should be advised of warning signs of these serious potential complications.
| Slipped, Lost and Stretched Muscles|| |
The slipped muscle
A slipped muscle is a disinserted rectus muscle, which, after reattachment to the globe, retracts posteriorly within its muscle capsule, while the empty capsule remains attached to the sclera at the intended new insertion site. A slipped muscle should be differentiated from a lost muscle in which no portion of the muscle, including its capsule, remains attached to the sclera.
Typically, the patient presents shortly after strabismus surgery with a moderate to large consecutive deviation and a small to medium duction deficit. Usually, the distinction between a slipped versus a lost muscle can be made during clinical examination. Although the patient may have a large consecutive deviation, the duction deficit may be less than would be expected if the muscle was completely detached from the globe. At the time of surgical exploration, the surgeon should anticipate finding the muscle capsule attached to the globe at or near the intended location for muscle placement during the previous surgery. Once the muscle capsule is located, it is carefully followed posteriorly where the muscle/tendon itself will be found attached to muscle capsule. The muscle should be isolated, secured with sutures, and brought back in contact with the globe. ,
In theory, a slipped muscle should be a preventable event. Full thickness locking bites which incorporate the muscle, and not just the muscle capsule, should prevent the muscle from slipping within its muscle capsule. If the muscle capsule is thick, making clear identification of the muscle difficult, the anterior portion of the muscle tendon should be cleaned of fascial attachments to allow more precise placement of sutures in the muscle tendon.
The lost rectus muscle
Unlike a slipped muscle, when an extraocular muscle is lost, no direct attachment remains between the muscle tendon and the globe. The muscle and its capsule both retract posteriorly into the orbit.  A patient with a lost muscle generally presents within hours or days after surgery with a large consecutive strabismus and an associated large duction deficit in contrast to the small duction deficit usually seen with a slipped muscle.
If an extraocular muscle is lost during surgery, it should be retrieved immediately if possible. Generally, exposure of the surgical site is better at the time of the initial surgery and the newly exposed tissue planes may make identification and retrieval of a lost muscle easier than if surgical repair is attempted hours or days later. The surgeon should avoid purposeless exploration in search of a lost muscle, a practice that can significantly worsen the situation, resulting in hemorrhage, fat intrusion into the surgical site, and other complications. If the operating surgeon is not familiar with the techniques of exploration to locate a lost extraocular muscle, it is the best to finish the intended surgical procedure and refer the patient to a skilled strabismus surgeon as soon as possible. Though optimal to make the repair during the initial operation, later repair is far superior to the damage that may occur during aimless exploration
If the muscle capsule and intermuscular septum have undergone extensive dissection prior to the muscle being lost, the muscle will commonly retract through Tenon's capsule to enter the posterior orbit. The surgeon should identify the potential space within Tenon's capsule through which the muscle has retracted. Repair is optimally carried out through a large limbal incision. The basic steps required to locate a lost muscle in this situation involve retraction of the conjunctival flap and Tenon's capsule anteriorly to expose the global surface of Tenon's capsule. The global surface of Tenon's capsule is visually inspected and delicately manipulated with fine toothed forceps in an attempt to locate the potential space representing the ruminants of the muscle capsule passing through Tenon's capsule. A common mistake is to attempt to locate the lost muscle along the surface of the globe posteriorly. Rather, the surgeon should recognize that the paths of the extraocular muscles are guided and restrained by the rectus muscle pulley system and instead of coursing along the globe, the rectus muscles course posteriorly and toward the adjacent orbital wall to enter the pulley mechanism [Figure 3]. If the surgeon is unable to locate the lost muscle during the course of the exploration, a decision must be made whether to proceed with alternative treatment, such as a muscle transposition procedure, or to defer surgery to another day when further evaluation and other treatment modalities may be available to assist in the repair.
|Figure 3: Identification and retrieval of a lost muscle. (a) A lost rectus muscle will be found along the adjacent orbital wall. (b) A common mistake is to search for the muscle along the posterior aspect of the globe (with permission from Coats DK, Olitsky SE, Strabismus surgery and its complications, Springer 2007)|
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In most cases, intraoperative loss of an extraocular muscle can be avoided with proper surgical technique. Careful identification and isolation of the rectus muscle during surgery is an important step in the prevention of accidental detachment of a muscle. An important preventive measure in reducing the risk of a lost muscle during rectus muscle recession surgery is to limit dissection of the posterior intermuscular septum, muscle capsule, and check ligaments. Excessive dissection of these structures does not enhance the effect of recession surgery but increases the chance that the muscle will retract into the posterior orbit if control of the distal aspect of the muscle is lost.  Sutures used during strabismus surgery should be handled carefully, preferably with smooth instruments, as instruments with teeth and rough edges can result in damage to the suture material, causing weakness of the suture, reducing its tensile strength with resulting reduction in the strength of the new muscle attachment to the sclera.
Stretched scar syndrome
Patients who develop a stretched scar following strabismus surgery may have a similar presentation to patients who have a slipped muscle. , However, the overcorrection with a slipped muscle typically occurs shortly after surgery. In contrast, overcorrection in stretched scar syndrome usually occurs several months later. At the time of reoperation, an amorphous scar tissue separating the muscle tendon from the scleral attachment site is generally found. It is postulated that scar lengthening after surgery is responsible for the recurrent deviation.
Diagnosis of stretched scar syndrome can be suspected but cannot be confirmed until the time of surgery to repair the deviation. During the surgical procedure, the distinction between the scar and the muscle tendon may be subtle. The scar can gradually blend into the tendon because the fibers of the scar often run parallel to the fibers of the tendon.
The scar should be excised in its entirety after placing sutures in the muscle tissue posterior to the scar. The muscle is then reattached to the globe. Failure to remove the scar completely increases the risk of recurrence.
| Fat Adherence Syndrome|| |
The term fat adherence syndrome refers to a progressive restrictive strabismus associated with the entrance of extraconal orbital fat into the sub-Tenon's or episcleral space following orbital surgery or trauma. Exposed extraconal fat that enters the episcleral space can come into contact with the extraocular muscles, the sclera and/or other orbital connective tissue elements. A fibrous scar develops which is attached to the orbital periosteum. This scar then contracts and leads to progressive strabismus with inhibition of ocular movement. The entrance of extraconal fat into the episcleral space occurs secondary to a disruption in posterior Tenon's capsule, which normally acts as a barrier to fat entering this location.
The best method to prevent the development of fat adherence syndrome is to avoid damage to posterior Tenon's capsule during strabismus surgery. This is especially true during inferior oblique surgery, where damage to posterior Tenon's capsule is most likely to occur.  Direct visualization of the posterior border of the inferior oblique muscle during its isolation can help to reduce the risk of penetrating Tenon's capsule Blind sweeps of the inferotemporal quadrant to isolate the inferior oblique muscle are discouraged. If a defect in posterior Tenon's capsule is noted during surgery, it should be treated. It may be possible to reposition small amounts of orbital fat that protrude through a rent in posterior Tenon's capsule back into the extraconal space followed by closure of the rent. If a large amount of extraconal fat has entered the episcleral space, a hemostat can be placed across the fat at the opening of the defect and excised. The defect in Tenon's capsule can then be sutured closed using absorbable sutures.
| Eyelid Retraction and Advancement Following Vertical Rectus Muscle Surgery|| |
0The external aspect of the sheath of the vertical rectus muscles is adherent to the internal surface of the eyelids. The surgeon must be aware of these connections because they can have important implications for the patient following vertical rectus muscle surgery. Postoperative alteration of the position of the upper and lower eyelids is the most common eyelid abnormality that occurs following strabismus surgery. Bothersome alteration of eyelid position is less likely to occur following recessions and resections of 5 mm or less. Patients who are at greatest risk of developing eyelid retraction are those undergoing very large recessions.
Generous dissection around of the attachments between the vertical rectus muscles and the eyelids can be performed at the time of surgery to prevent postoperative eyelid changes.  Care should be taken during posterior dissection of the attachments not to disturb the vortex veins that are usually found adjacent to the medial and lateral borders of the muscle.
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[Figure 1], [Figure 2], [Figure 3]