Complications of Strabismus SurgeryAbstractINTRODUCTIONIt is said that the only surgeons who do not have complications are those who do not operate andthose that lie about having no complications. All surgeries carry risks of complications, and thereis no way to avoid ever having one. Strabismus surgery is no different in this regard. There aremethodstoreducetheriskofacomplicationduringoraftersurgery,andthesestepsshouldalwaysbetaken. Whenacomplicationoccurs, it isimportant tofirst recognizeit andthenmanage it appropriately to allow for the best outcome possible. This article will discuss some ofthe more common andor most devastating complications that can occur during or afterstrabismussurgeryaswell asthoughtsonhowtoavoidthemandmanagethemshouldtheyhappen.ANTERIOR SEGMENT COMPLICATIONSDellen!ellenarecharacterizedasshallow,clearlydefinede"cavationsat themarginofthecornea.Theyare generally#.$%&mmin diameter and occur following localized evaporationanddehydration of the cornea. 'esulting disruption of the tear film and localized evaporation resultin increasing compactness of the corneal stromal lamellae.When dellen occur following strabismus surgery, they typically develop within the first & weeksand tend to occur more fre(uently on patients operated with a limbal approach compared to thoseoperated using a nonlimbal approach.#,& !ellen probably often go undiagnosed becausesub)ective symptoms may be absent, clinical findings may be subtle, and strabismus surgery isoften performed on small children who cannot be readily e"amined at a slit lamp. The occurrenceof dellen is much more common following resection procedures compared to recessionprocedures and are much more likely to occur following very large resections. Their formationfollowinghorizontal rectusmusclesurgeryisnotuncommon, but it isveryraretoseeaftervertical rectus muscle or obli(ue muscle surgery.Treatment ofdelleninvolvescorneal rehydrationandmeasurestoreducelimbalcon)unctivalelevation. A lubricating ophthalmic ointment usually leads to resolution within a few days to aweek, accompanied by spontaneous reduction in bulbar con)unctival swelling as postoperativehealing progresses. *atients with an underlying tear film deficiency may be at higher risk andre(uire closer follow+up.INADVERTENT ADVANCEMENT OF THE PLICA SEMILUNARIS CONJUNCTIVAEInadvertent advancement plica semilunaris con)unctivae ,oftensimplyreferredtoas plica-typicallyresults fromthesuturingof plicatothecon)unctivaad)acent tothelimbus. Thiscomplication may occur following strabismus surgery using a limbal incision. !uring standardlimbal surgery, the anterior aspect of the limbal con)unctival flap becomes folded beneath theplica. At the conclusion of the surgery, the surgeon attempts to identify the anterior edges of thecon)unctival flap. Theplicamayhavebecomehydratedandswollenduringsurgeryandthesurgeon mistakenly believes that heshe has grasped the anterior corners of the con)unctival flap,when in fact the edges of the plica have been inadvertently grasped. .igure # demonstrates howeasily this can occur. /nly by careful study of the anatomy will the surgeon recognize that themedial angleoftheeyeappearsabnormal andthat theswollenplicahasbeeninadvertentlyadvanced forward. /nce the mistake is recognized, key landmarks can be easily identified..igure #,a-Inadvertent advancement oftheplicasemilunarisduringclosureofalimbal incision0 ,a-Appearance of the medial angle of the con)unctiva when the plica is held against the limbus,demonstrating how the surgeon can be fooled into believing that ...This complication may be more likely following prolonged surgery and is most prone to occurafter an e"tensive reoperation and in older patients with e"tremely thin con)unctiva. The use ofe"cessive hydration during surgery may result in greater distortion of the anatomy by increasingedema of tissues in the operative site.*revention of inadvertent advancement of the plica should begin before surgery is initiated. Thesurgeon should e"amine the anatomy of the medial aspect of the eye and take care to restore theanatomytoitspreoperativestateat thetimeofclosure. Incaseswhereadifficultclosureisanticipated a sterile methylene blue skin marking pen can be used to mark the anterior corners ofthe con)unctival flap before proceeding with surgery. At the conclusion of the case, these cornermarkers are easy to locate, and they help facilitate accurate con)unctival closure.CHEMOSIS1hemosis occurs toa milddegree inall patients undergoing strabismus surgery, but canoccasionally be pronounced. Severe chemosis is rarely seen following routine strabismus surgerybut can disrupt the suspensory attachments to the con)unctival forni" through hydraulicdissection. *rolongedprolapseofthecon)unctivamayresult infusionofthefoldstogetherre(uiring e"cision.2 Treatment is initially supportive, consisting of aggressive lubricatingophthalmologic ointments, with the addition of cellophane tents at night if the swollencon)unctiva protrudes anterior to the eyelids. Topical steroids are often prescribed and appear tobe of value. This conservative treatment regimen will usually result in significant improvementor resolution within a few days to a week.Py!en"c !ran#l$a*yogenic granulomas appear as a fleshy red mass with relatively rapid growth. The lesion is aproliferative fibrovascular response to previous trauma including surgery. In most cases, theselesions will resolve spontaneously. 3anysurgeons recommendthe use of topical steroidsalthoughtheirefficacyhasnot beenproven. Surgical e"cisionmaybere(uiredforpyogenicgranulomas that fail to resolve after topical treatment alone. 'eoccurrence following e"cision israre.E%tr#&e&'e%(se& Tenn)s *asc"a/ccasionallye"trusione"posure of Tenon4s fascia throughthe con)unctival incisionoccursfollowing strabismus surgery. This complication can be avoided by ensuring that the edges of thecon)unctival incision are well opposed or sutured following surgery. If a large amount of Tenon4sfasciaisnotedtobee"trudingthroughthecon)unctival incisionat theendofthecase, thesurgeon can either e"cise the e"truding Tenon4s fascia or place additional sutures in thecon)unctiva to fully internalize the e"posed fascia. /ccasionally, however, a patient will presentpostoperatively with e"posed Tenon4s fascia, sometimes with the e"posed Tenon4s fasciastringing from the wound and even overhanging the eyelid. The e"posed Tenon4s fascia can betrimmed flush with the con)unctival surface. Topical steroids can be used in cases where e"cisionis not possible, and resolution typically occurs within days or weeks.E("t+el"al "ncl#s"n cystSubcon)unctival epithelial inclusioncystsoccurinfre(uentlyasacomplicationofstrabismussurgery. They can occur anywhere in the operative field, but most commonly occur ad)acent tocon)unctival incisions or near the new muscle insertion into the sclera. These cysts are thought toarise from inclusion of con)unctival epithelial cells into the substantia propria or the sclera. 5estsof con)unctival epithelial cells that havebecome depositedduringstrabismus surgerylaterproliferate, formingacentral cavityandultimatelyformingavisiblecyst. Ifthecon)unctivabecomes adherent to the suture and is pulled into the scleral tunnels, con)unctiva epithelial cellsmay become deposited in the scleral tunnels and allow a cyst to form 6.igure &7..igure &!ragging of the con)unctiva into the scleral suture tunnels which could implant epithelial cellsinto the scleral tracts and lead to epithelial cyst development ,with permission from 1oats !8,/litsky S9, Strabismus surgery and its complications, Springer ...When an epithelial inclusion cyst forms at the site of muscle reattachment to the sclera failure torecognize that the muscle is attached to the cyst can result in detachment of the muscle. Whileverysmall epithelialinclusioncystscan be effectively removed through asmallcon)unctivalincisionplacedad)acenttothecyst, most mediumtolargeepithelialinclusioncystsarebestremoved through a standard limbal con)unctival incision, similar to the limbal incisions createdforsurgeryontherectusmuscles. :imbalincisionsallowthesurgeontomaintaincontrolofad)acent muscles during e"cision. Isolation of the ad)acent muscle on a muscle hook can helpensure the safe removal of the cyst without accidental disinsertion of the muscle if the cyst islargeandlocatedclosetothemuscle. Thegoal of surgeryshouldbetoremoveepithelialinclusion cysts intact. 3anipulating the cyst with forceps should be avoided as the cyst can easilyberuptured. /ncethecyst hasbeenfullye"posed, it shouldbecarefullye"cisedfromtheunderlying sclera. Attachment of the cyst to the underlying sclera is typically very firm and caremust betakentotransect thesefinebut firmattachments totheunderlyingsclerawithoutrupturingthecyst. If thecyst ruptures duringremoval, everyattempt toe"ciseall visibleelements of the cyst should be made along with irrigation of the operative site in an attempt towashawayanystrayepithelial cells, andappliedcauterytothesclerawherethecyst wasattached. A nonsurgical option for the management of epithelial inclusion cysts is aspiration ofcyst contents, intracyst in)ection of alcohol which is then left in the cyst for several minutes, andthen aspiration of the alcohol.ANTERIOR SEGMENT ISCHEMIAAnterior segment ischemiaisararebut potentiallysight+threateningcomplicationfollowingstrabismus surgery.; 'iskfactors for thedevelopment of anterior segment ischemia includeadvanced age, previous rectus muscle surgery and history of a vasculopathy, such as diabetesandor hypertension. /f these risk factors, advanced age and the number of rectus muscles beingoperated upon appear to be the most important. Surgery on an ad)acent vertical and horizontalrectus muscle is more likely to lead to an observable effect on anterior segmentcirculation.$,< !etachment of three or four rectus muscles at one time carries a significant risk ofcompromising the vascular supply of the anterior segment in some patients.A history of prior e"traocular muscle surgery should be taken into account when weighing therisk of anterior segment ischemia developing if further surgery is planned. A direct connectionbetween 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 anteriorsegment ischemia. This is especially true if further surgery involves detachment of the third orfourth rectus muscle in the same eye. 'epeat surgery on a previously operated rectus musclesdoes not itself increase the risk of anterior segment ischemia since reestablishment of blood flowthrough the previously disrupted anterior ciliary artery does not occur.=nderlying vascular disease plays an important role in determining which patients are most atriskforanteriorsegment ischemia. *atientswithco+e"istent vasculardiseaseincombinationwithother aforementionedriskfactors areconsideredat greatest riskfor anterior segmentischemia. 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.3ild cases with reduced iris perfusion may be demonstrated only with iris angiography whilemoreseverecasesmayincludechangesinpupil shapeandreactivity, postoperativeuveitis,cataract, keratopathy, hypotony and eventual loss of vision and even phthisis bulbi in rare cases.>ecause the signs of anterior segment ischemia are similar to those seen in more typical uveitis,many ophthalmologists treat empirically with corticosteroids. 3ild anterior segment ischemia isgenerally treated with topical agents, and more severe cases are often treated with oralcorticosteroids. Therearenodatatosuggest that anyspecifictreatment ofanteriorsegmentischemia improves the outcome of this disorder.Thebest treatment for anterior segment ischemiais prevention. Asurgical planfor at+riskpatients should be designed that will minimize the risk that clinically significant anterior segmentischemia will develop. *otential strategies include limiting the number of rectus muscles that aredetachedfromtheglobe, techni(uestopreserveanteriorciliaryarteriesandstagingsurgicalprocedures when needed.?,@SCLERAL PERFORATIONThe reported incidence of scleral perforation varies widely. 'etrospective studies and sur veysarelikelytogreatlyunderestimatethenumber of scleral perforations anddeeppasses thatactually occur. /ne prospective study found the incidence of scleral perforation to be $.#A.BTheriskofscleral perforationappearstobegreatestduringreattachmentofamuscletothesclera, where the needle must carefully penetrate the sclera, but only deep enough to secure themuscle to the globe. The margin of error may be very small in eyes with a thin sclera. Scleralperforation probably occurs more commonly during recession than during resectionsurgery.#C This is presumablybecause e"posure of the surgical site is more difficult withrecession surgery.'ecognition of a perforation is necessary before potential treatment can be considered. Scleralperforation probably goes unrecognized in many cases. Intraoperative signs of a scleralperforation may vary depending on the patient and the severity of the perforation. The surgeonoften DfeelsE that the needle pass was too deep and is immediately suspicious that a perforationmay have occurred. 'ecognized scleral perforations are often heralded by a small piece of uveaor a bead of vitreous on the tip of the suture needle. Indirect ophthalmoscopy to inspect the retinaunderlying the surgical site should be performed when a scleral perforation is suspected. 3ostscleral perforations are small, even microscopic. :acerations of the sclera and even unintentionalblockresectionsofthescleracanoccurduringstrabismussurgery,andthesurgeonmust beprepared to manage this complication or have access to a consultant surgeon. If a large retinaltear is noted, or if a small retinal tear is noted in a patient at high risk for retinal detachment,laser retinope"y may be re(uired and the patient should be followed closely during thepostoperativeperiodforevidenceofendophthalmitisandorretinal detachment.A childwithwell+formed vitreous is probably at low risk for detachment and laser may not be necessary.>ecause the needles and sutures used during strabismus surgery are often contaminated duringsurgery, it may be good general practice when a perforation is suspected to withdraw the needleand suture and reposition it in an alternative location.##,#& In addition, antibiotic drops andor $Apovodine+iodinesolutioncanbeappliedtotheoperativesite. Somesurgeonswill administersubcon)unctival antibiotics, a dose of intravenous antibiotics andor prescribe prophylactictopical andor oral antibiotics postoperatively. There is no scientific data to validate any specificprotocol.*robablythemost important steptotakeafterascleral perforationhasbeenidentifiedistoinform and educate the patient andor family so that they are aware of the potential for a seriouscomplication and understand the signs and symptoms of endophthalmitis and retinal detachmentin the rare event that one of these complications occurs and follow the patient carefully. 1arefulsurgical planning and techni(ue are both important in preventing scleral and eye wall perforationduringstrabismus surgery. 3aintainingade(uatesurgical e"posureandusingproper needlepassing techni(ues are important to reduce the risk of perforation. The surgeon should avoid thetendency 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 atvirtually any time of surgery. The use of a hang+back recession techni(ue may be helpful as itallowse"cellent e"posureregardlessoftheamount ofrecessionbeingperformed. Itsuseinpatients believed to be at higher risk for scleral perforation should be specially considered.POSTOPERATIVE INFECTIONSerious infections following strabismus surgery are uncommon. 3ost busy strabismus surgeonsare unlikely to see more than one or two cases of endophthalmitis andor orbital cellulitis duringtheir entire career. /ther important, but less serious infections, such as preseptal cellulitis andsubcon)unctival abscesses, are more common. 9ndophthalmitis is so rare after strabismus surgerythat it is often initially misdiagnosed. The visual outcome of endophthalmitis followingstrabismus 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 commonsource of viable organisms producingendophthalmitis after strabismussurgeryisnotknown. *otential sourcesofinfectionincludethenormal bacterial floraintheregion of the operative site, contaminated surgical material, postoperative periocular abscess, andtransient endogenousbacteremia. 3ost oftheavailabledataonriskfactorsforsurgical sitecontamination and for risk of endophthalmitis following ophthalmologic surgeryrelate tocataract surgeryandotherintraocularsurgical procedures. Thoughuncomplicatedstrabismussurgery does not result in perforation of the sclera, the strabismus surgeon should still be awareof these reports.The surgeon4s hands are an important potential source of bacterial contamination during surgery.Flove perforation during surgery occurs more fre(uently than surgeons may realize and gloveperforation not only e"poses the patient to contaminants on the surgeon4s hands but also e"posesthesurgeontopotentiallyinfectedpatient tissues andbodyfluids. Floveperforationoftenhappens while handling suture needles. Sutures should be loaded onto the needle holder withoutever touchingtheneedle itself. *lacement of aneedleintoaneedle holder canbe easilyfacilitated by holding the suture material close to the needle. Golding the needle in one4s handwhile placing it into the needle holder or passing it off the operative field is a common, but verypoor, practice. It e"poses both the patient and operating room personnel to unnecessary risk.Instruments, implants, e"plants, andsurgical supplies canbecomecontaminatedduringanysurgical procedure through several potential mechanisms. The ocular adne"a and con)unctiva ofthe patient are prime sources of potential contamination during ophthalmologic surgery. The rateofneedlecontaminationduringstrabismussurgeryhasbeendemonstratedtobe#$Ainonestudy.## Fiven the fact that the sutures and needles used during surgery have a high potential tobecome contaminated with bacteria during routine strabismus surgery, steps to reduce the risk ofe"posure to contaminated needles and sutures should be considered. Isolation of the eyelids andlasheswithanadhesivedrapemayreducethepotentialforcontaminationduringophthalmicsurgerythough thereis noevidencethatthismeasure reducesthe riskof infection relatedtostrabismus surgery. If a scleral perforation is suspected or confirmed during surgery, the surgeonshould consider halting passage of the needle and withdraw it immediately before potentiallycontaminated suture material is drawn through the perforation site. :ikewise, if the needle hasalready been passed through the sclera, it may be prudent to cut the suture flush with the scleraand remove it, to avoid having to draw additional potentially contaminated needle and sutureback through the suspected perforation site to remove it. :eaving a foreign body ,suture- in ascleral perforation site has the potential to increase the risk of infection, and thus repositioning ofthe suture to another site should be considered.En&(+t+al$"t"sTheestimatedincidenceof endophthalmitis followingstrabismus surgeryranges from#in2$C,CCC cases suggested in #Bao.#BB#J?0;2%r K /phthalmol.#B?$J$B02??%B. 6*31 free article7 6*ub3ed72. >iglan AW, 1hang A, Giles !A. *rolapse of con)unctiva following e"ternal levator resection. /phthalmic Surg. #B@CJ##0$@#%2. 6*ub3ed7;. .rance T!, Simon KW. Anterior segment ischemia syndrome following muscle surgery0 The AA*/LS e"perience. K *ediatr /phthalmol Strabismus. #B@inocul Mis Strabismus N. &CC&J#?0&$%22. 6*ub3ed7&C. *lager !A, *arks 33. 'ecognition and repair of the slipped rectus muscle. K *ediatr /phthalmol Strabismus. #B@@J&$0&?C%;. 6*ub3ed7. *lager !A, *arks 33. 'ecognition and repair of the DlostE rectus muscle. A report of &$ cases./phthalmology. #BBCJB?0#2#%