7 Complications of Strabismus Surgery

Malcolm Ing


Infections following strabismus surgery may be mild (conjunctivitis), moderate (orbital cellulitis), or severe (endophthalmitis). Although rare, orbital cellulitis and endophthalmitis may result in vision loss—a potentially devastating complication of strabismus surgery. This chapter describes the methods the strabismologist may utilize to minimize the risk of infection and maximize the chance of recovery by early diagnosis and treatment. In addition, this chapter will describe techniques ophthalmologists can employ to avoid the rare but nonetheless severe complication of anterior segment ischemia following strabismus repair.

The author will also describe the techniques previously employed by investigators to meet the challenge of secondary surgery following complications of strabismus surgery. Subsequent attempts at realignment are often difficult because of the excessive scar tissue left from the previous surgery. As recognized by strabismologists, a second procedure may result in only temporary improvement in the ocular position. Often, there is regression into a less satisfactory alignment when the scar tissue is again allowed to interfere with the new alignment. A restriction of ductions caused by scar tissue is the major challenge the strabismologist must face in attempting to improve globe mobility. Scar tissue may result from fat adherence syndrome, loss of elasticity of the septa in the extraconal space from previous inflammation, shortened conjunctiva, and adhesions between recti, as well as to the underlying sclera. Two substances, 5-fluorouracil and mitomycin C, have been used intraoperatively by some investigators in animal experiments in attempts to prevent secondary scarring. Amniotic membrane and conjunctival autografts have also recently been employed to manage the scar formation in restrictive strabismus. The relative value of each of these endeavors will be discussed.

7 Complications of Strabismus Surgery

7.1 Introduction

The different types of infection following strabismus surgery and anterior segment ischemia (ASI) are described in this chapter. Infections may be superficial or much more serious. Orbital cellulitis is rare (1/1,000–1/1,900) after strabismus surgery but may result in vision loss. Endophthalmitis is more rare (1/30,000–1/185,000) than cellulitis, and presents with an anterior chamber hypopyon and vitreous haze. Intraocular infection may result in loss of all vision in the affected eye. All strabismologists would agree that, aside from the death of a patient from anesthesia, endophthalmitis, which results in a blind painful eye, is the most devastating complication of strabismus surgery for the patient, family, and surgeon. It behooves the strabismologist to detect and treat these severe complications as early as possible to prevent vision loss.

ASI is another rare but serious complication. Techniques to avoid this complication are available, and these endeavors will be discussed in detail in this chapter.

7.2 Types of Infection following Strabismus Surgery

7.2.1 Conjunctivitis

The true incidence of postoperative superficial infections, conjunctivitis, and blepharitis is difficult to determine. Nevertheless, approximately 3% of strabismus surgical cases developed clinical signs of conjunctival infection following strabismus surgery in a retrospective study of 1,603 patients reported on by Koederitz et al. 1 Most surgeons select a mixture of postoperative topical antibiotics, sometimes combined with steroids, to use for several days to weeks to minimize the possibility of infection. This practice persists despite the fact that the prophylactic value of topical antibiotics has been questioned following the results of a prospective randomized study that showed no significant difference in the rate of infection when topical antibiotics were compared to artificial tears. 2 It should also be mentioned, however, that another study comparing topical antibiotics to no topical antibiotics was interrupted when three of eight patients who were not receiving topical antibiotics developed severe mucopurulent discharge following strabismus surgery. 3 Most strabismus surgeons close the conjunctival wounds with sutures and use topical antibiotics in an effort to minimize entry of bacteria under the conjunctiva after surgery. There was no significant difference in infections treated with single-dose postoperative topical povidone iodine versus multiple daily antibiotic drops in the Koederitz retrospective study. 1 The fact remains that infections may still occur despite intact wounds with or without the use of antibiotics.

The topical use of preoperative povidone iodine solution to reduce the preoperative conjunctiva bacteria by 91% has been shown by Apt et al and Isenberg et al. 4 ,​ 5 Subsequent to the published studies showing the value of preoperative topical povidone iodine in reducing infections in cataract surgery, the use of this solution prior to surgery has also become routine for most strabismus surgeons. 6 Surgeons should remember that, for sufficient reduction of conjunctival bacteria, there must be at least 2 minutes’ exposure to the povidone iodine solution on the surface of the eye.

A rare type of surface inflammation, ligneous conjunctivitis, has also been reported after strabismus surgery. 7 Typically, this inflammation, which is of unknown etiology, does not respond to topical antibiotic-corticosteroids. Fortunately, topical cyclosporine 2% has been found to be helpful in clearing the inflammation.

7.2.2 Scleritis

Necrotizing scleritis is a rare complication following strabismus surgery. This complication presents several weeks following strabismus surgery, which serves to differentiate this serious event from orbital cellulitis, ASI, and endophthalmitis, which usually occur within the first few days after surgery. 8 ,​ 9 ,​ 10

Common diseases that predispose patients to develop necrotizing scleritis include systemic autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, periarteritis nodosa, Wegener granulomatosis, and thyroid orbitopathy. Diabetes mellitus, with compromised circulation, is another risk factor.

Diagnostic studies with B-scan ultrasonography may reveal thickening of the choroid in necrotizing scleritis.

Treatment consists of corticosteroids, both topical and systemic, along with nonsteroidal anti-inflammatory agents, cycloplegics, and cytotoxic agents. Despite the use of these agents, however, the condition may persist and recur for years, and in some cases, vision may be lost or the eye may require scleral grafting or enucleation.

7.2.3 Sub-Tenon’s Abscess

There have been six reports of sub-Tenon’s abscess following strabismus surgery. 11 ,​ 12 ,​ 13 ,​ 14 ,​ 15 ,​ 16 This complication, which may be bilateral, presents as a rapidly developing, localized painful swelling in the region of an extraocular muscle. The presentation of sub-Tenon’s abscess differs from orbital cellulitis in that the latter presents with more generalized swelling rather than a localized area of inflammation. In all reported sub-Tenon’s abscesses, systemic antibiotics were utilized, but resolution only occurred after performing an incision and drainage procedure, usually from 1 to 10 days postoperatively. The outcome was favorable, without vision loss or compromise of alignment.

7.2.4 Orbital Cellulitis

There is a low incidence of orbital cellulitis following strabismus surgery. 17 This complication was reported in 12 cases in a large series of 12,263 patients at Columbia Presbyterian Hospital in New York, for an incidence of approximately 1 per 1,000 cases. 18 In a survey of the Costenbader Society members, Ing reported an incidence of orbital cellulitis of 1/1,900 cases. 19

Because the incidence of orbital cellulitis is so low, a pooled analysis of the experience of a group of ophthalmologists has been useful. A large questionnaire study of orbital cellulitis was conducted by Kivlin, Wilson and the Periocular Infection Study Group. 20 In the Kivlin study, 308 pediatric ophthalmologists responded, and 25 patients were diagnosed as having orbital cellulitis based on definite evidence of infection deep to the conjunctiva. The clinical diagnosis was supported by swelling and pain around the eye, especially when compared to the other eye in binocular cases (Fig. 7‑1).

Fig. 7.1 Bilateral orbital cellulitis 7 days after recession of both medial rectus muscles. (Courtesy of Sharon Freedman, MD.)

Kivlin et al reported that over 50% of those ophthalmologists surveyed, with a mean of 13 years in practice, did not find any postoperative orbital cellulitis in their patients. Among those surgeons who did report cases, 128 infections occurred over 3,983 years of practice, for approximately 1 case per 32 years of practice. Ten of the 25 reported cases had imagery with computed tomography (CT) or magnetic resonance imaging (MRI), which supported the diagnosis of orbital cellulitis. Most of the cases developed signs and symptoms before the fourth postoperative day. Although two-thirds of the patients were diagnosed by the second postoperative day, the other third had the diagnosis made after the second postoperative day. This finding means that patients can appear to be free of orbital infection early in the post operative course, but subsequently develop this complication. Systemic clinical symptoms of fever, loss of appetite, nausea, and lethargy or irritability were present in half of the patients. In the Kivlin series of patients, the most common offending organism by conjunctival culture was Staphylococcus aureus. One-third of the conjunctival cultures were negative, and only 1 patient (out of 10 tested) had a positive blood culture for S. aureus. Oral antibiotic treatment was attempted in 11 patients, but only thought to be efficacious in 3 patients. Among the systemic antibiotics found to be helpful, intravenous (IV) cefuroxime and IV ceftriaxone were the most commonly utilized. 20

Serious complications, such as meningitis, resulting in death of the patient have followed severe orbital cellulitis. Therefore, hospitalization and cerebrospinal fluid examination should be considered, especially in infants and children less than 5 years of age showing lethargy. 20

Unsuspected sinusitis was found in 3 of the 25 orbital cellulitis cases reported by Kivlin et al. Other predisposing factors were excessive eye rubbing and a respiratory infection that was either present or resolving at time of surgery. Preoperative examinations should rule out any upper respiratory infection; otherwise, surgery should be postponed until recovery. In the management of eye infections following strabismus surgery, any subconjunctival abscess should be drained surgically, particularly if it does not respond rapidly to systemic antibiotics, in order to prevent scleral necrosis. 20

Managed well, infected orbital cases may have a satisfactory result. Indeed, somewhat surprisingly, 18 (72%) of the treated patients in the Kivlin et al report had the alignment results expected by their surgeons, signifying that orbital cellulitis following strabismus surgery does not preclude a good result. Furthermore, none of the patients developed endophthalmitis, although it has been reported that removal of an infected suture with a surrounding abscess did promote healing and resolution of early endophthalmitis in a case observed by Dr. Robert Reinecke. It is certainly possible that delayed diagnosis and treatment in these cases might have led to endophthalmitis. 20

7.2.5 Endophthalmitis

The incidence of endophthalmitis was estimated to be 1 per 30,000 cases in the Costenbader Society members survey by Ing. 19 There are very few reports of endophthalmitis following strabismus surgery in the medical literature. It may be useful to summarize the findings in the four cases reported on by the authors who have published the results in their patients. 10 ,​ 21 ,​ 22 ,​ 23 Signs and Symptoms

All patients had decreased vision and severe pain and swelling around the infected eye. Onset

The onset of endophthalmitis was reported to be present on postoperative day 3 through day 10. Presence of Hypopyon

All patients had a hypopyon or fibrin in the anterior chamber in the affected eye on initial exam by the ophthalmologists. Presence of Vitreous Haze

All patients had vitreous haze in the affected eye at the time of diagnosis. Scleral Perforation

Two of the four cases were recognized to have a scleral perforation at the time of strabismus surgery. Both patients had cryopexy around the lesion at the time of recognition of the perforation. In the other two patients, no perforation was detected at the time of the strabismus surgery. Culture Result

Positive vitreous aspirates showed different offending organisms: Staphylococcus epidermidis in two cases and Streptococcus pneumoniae in one. No vitreous tap and culture was reported for one case. Treatment and Course Case 1

For this patient, 100 mg of subconjunctival cephaloridine and 40 mg of gentamicin was given on the first day of diagnosis (third postoperative day). Twice-daily subconjunctival cephaloridine and gentamicin was augmented with an intravitreal injection of 250 µg of cephaloridine and 400 µg of gentamicin. Vitreous culture grew S. epidermidis, sensitive to all antibiotics tested. This patient also received IV administration of gentamicin 80 mg every 8 hours and cephaloridine 2 mg every 6 hours. On the fourth day after strabismus surgery, a vitrectomy was performed due to increased vitreous haze. A large horseshoe tear with a shallow detachment of the retina was found at that time, and the eye was treated by additional intravitreal gentamicin and a cryopexy. The patient was discharged on the 12th postoperative day with light perception vision. Six weeks later, a detached retina developed and the eye was treated by membrane peeling, scleral buckle, and an air/fluid exchange. During the following weeks, a cyclitic membrane developed and, although the retina was attached, the patient could only see light with projection with the affected eye. Case 2

This patient had an uneventful bi–medial rectus recession. She had no findings of post operative complications when seen the day after surgery. However, this patient was not seen by the surgeon until 10 days after surgery, at which time, one eye was very painful and the vision had decreased to hand motions. Fibrin was noted in the anterior chamber and the vitreous was reported to be hazy. The patient was hospitalized, and chloramphenicol 500 mg and erythromycin 500 mg orally was administered every 6 hours. Topical steroids were administered throughout, and oral antibiotics were continued for 17 days and later tapered. No vitreous paracenteses or culture was reported, and no intravitreal or IV antibiotics were given. Despite the course of treatment, the eye developed a cyclitic membrane and was enucleated as a blind, painful eye 8 years later. Case 3

Routine povidone iodine was utilized preoperatively in this patient who had uncomplicated bilateral strabismus surgery. Postoperatively, a mixture of polymyxin B sulfate, bacitracin zinc, neomycin sulfate, and hydrocortisone ointment was topically administered for both eyes. Over the next several days, one eye developed periocular swelling and tearing. When the patient was seen on the fifth postoperative day, the vision in the affected eye was only light perception, the anterior chamber had a 10% hypopyon with marked flare, and the iris and lens were not visible due to a plasmoid aqueous. Ultrasonography revealed marked vitreous debris. The patient was treated with an anterior chamber paracentesis and removal of a fibrin clot, as well as a core vitrectomy with intravitreal injection of vancomycin hydrochloride (1 mg/mL) and 400 µg (0.1 mL) amikacin sulfate. Subconjunctival vancomycin hydrochloride (25 mg/0.5 mL), ceftazidime (100 mg/ 0.5 mL), and dexamethasone phosphate (6 mg/0.25 mL) was also injected. Despite the fact that the eye was comfortable the following day, the vision was reported to have no light perception. Culture results of the vitreous aspirate showed probable S. pneumoniae, which was found to be sensitive to all the antibiotics utilized, and the patient was started on IV cefazolin every 8 hours, which was continued throughout the hospitalization. By the end of 2 weeks, the eye was comfortable, but it never regained light perception. Follow-up visits revealed a dense cataract and vitreous debris but no retinal detachment. Case 4

The patient was recognized to have a scleral perforation at the time of surgery. The area of the perforation was treated by a transscleral retinal cryopexy after this discovery. The patient was treated postoperatively with topical antibiotic-steroid drops on the operated eye. On the third postoperative day, the eye developed pain, increased lid and conjunctival swelling, and a marked decrease in vision. When examined that same day, the cornea was edematous, and a 1-mm hypopyon was seen in the anterior chamber. Posterior pole examination showed only a barely visible red reflex. The diagnosis of endophthalmitis was made, and the patient was taken to the operating room that afternoon for a trans–pars plana vitrectomy and treatment with intravitreal and subconjunctival antibiotics. The culture of the vitreous aspirate grew out S. epidermidis, which was sensitive to most antibiotics. The patient was maintained for 5 days on IV antibiotics and systemic steroids, as well as topical steroids and hyoscine, with gradual clearing of the media. Two months later, an examination of the fundus was performed and two retinal breaks were identified with a small subclinical detachment of the retina. Cryopexy was applied under retrobulbar anesthesia. Three months after the core vitrectomy and the subsequent cryopexy, the best-corrected visual acuity was 20/50. The patient’s cataract had advanced by 8 months following the strabismus surgery and treatment for the endopthalmitis. An uneventful extracapsular cataract extraction with insertion of an intraocular lens was performed, which resulted in 20/20 visual acuity. Conclusion

Case 4 demonstrated that a good visual result may be obtained with prompt diagnosis and treatment; however, the majority of the cases had severe loss of vision. Ironically, Case 1 was also treated early in the postoperative course, on the third day following strabismus surgery, with a vitrectomy and intravitreal antibiotics. It is important to note that Case 1 was also similar to Case 4 because the vitreous cultures for both patients grew out S. epidermidis as the offending organism. In addition, both cases were recognized to have a scleral perforation at the time of strabismus surgery and both received cryopexy after this discovery. Neither of the cases received initial systemic antibiotics; however, both patients did receive systemic antibiotics and intravitreal antibiotics once the diagnosis of endopthalmitis was apparent. It is unknown whether or not systemic antibiotics given at the end of the strabismus surgery would have prevented the endopthalmitis that followed the perforations. It is important to note that, while both Case 1 and Case 4 were infected by the same organism and were treated in a similar manner postoperatively, the outcome was optimal in one and not in the other. Is Endophthalmitis following Strabismus Surgery Completely Preventable?

It is the author’s opinion that the answer to this question is probably not. Nevertheless, it is prudent to minimize the bacterial flora before and after the strabismus operation. Surgeons should avoid surgery in a patient with a known upper respiratory infection. Perforation of the sclera during strabismus surgery has been reported at a rate of 1 to 9%. 24 ,​ 25 ,​ 26 ,​ 27 In addition, culture of needle and/or suture material used in strabismus surgery has revealed up to a 30% contamination rate. 28 A study by Eustis and Rhodes showed that bacterial growth from the needles or sutures utilized during strabismus procedures could be reduced from 28% to 9% if these needles and sutures were soaked preoperatively in a solution containing povidone iodine (P = 0.006). 29 Perforations may occur despite the use of spatula needles to suture the muscle to the sclera. Occult choroidal and retinal breaks can only be detected by a dilated fundus exam with indirect ophthalmoscopy. This exam is preferably done at the completion of the strabismus procedure, especially if the sclera is thin at the site of the new insertion. When a small break in the sclera and choroid is revealed by the exam, the discretion of treating the break with cyropexy is best left to the surgeon, who may elect to treat or not depending on whether a definite retinal tear is present. Diligent postoperative follow-up is necessary to detect any signs of infection as early as possible to potentially save the vision in the affected eye.

Since endophthalmitis has been found to follow scleral perforations, it behooves the surgeon to closely follow the patient postoperatively with serial indirect ophthalmoscopy in any cases with known perforations. The surgeon should also remain alert to detect any increase in inflammatory signs and symptoms, especially any increase in pain and/or a decrease in vision. Orbital cellulitis, although rare, might possibly progress to an endophthalmitis. Surgeons who make the diagnosis of orbital cellulitis would be wise to promptly treat these cases with systemic antibiotics to minimize the chance for progression to a more serious infection.

7.3 Anterior Segment Ischemia

ASI is characterized by corneal edema, iritis, and pupillary distortion. This syndrome is related to the fact that the anterior ciliary arteries, which are embedded in the four rectus muscles of the eye, supply 70% of the blood to the anterior segment. 30

7.3.1 Causes of Anterior Segment Ischemia

The syndrome of ASI is diagnosed by the use of the slit lamp to look for corneal edema, iritis, and pupillary abnormalities. The sequelae of ASI may include corneal clouding, displaced or fixed pupil abnormalities, cataracts, hypotony, glaucoma, and phthisis. ASI, in general, may follow many clinical syndromes such as aortic arch syndrome, carotid artery obstruction, carotid-cavernous fistula, sickle cell disease, and thyroid-related orbitopathy, as well as cyclocryotherapy for glaucoma. 31 ,​ 32 ,​ 33 ,​ 34 ,​ 35 All of these clinical conditions share the predisposition to ASI because they lead to compromised anterior segment blood supply.

It was in 1941 that Leinfelder and Black reported that anterior segment changes in the eye could follow ocular surgery in experimental animals. 36 These anterior segment changes were not recognized to be ASI at that time by the investigators. In 1954, Chamberlain recognized that ASI could follow rectus muscle transposition in monkeys. 37 ASI was not recognized to exist following eye surgery in humans until Wilson and Irvine reported this clinical syndrome in 1955 following a retinal detachment repair in which several rectus muscles had been removed. 38 Stucchi and Bianchi reported ASI to be a potential complication of strabismus surgery in 1957. 39

The incidence of ASI is extremely low following strabismus surgery. A membership survey of the American Association for Pediatric Ophthalmology and Strabismus reported only 30 cases, at a rate of 1 per 13,000 strabismus procedures. 40

The pathophysiology of ASI in strabismus procedures is felt to be related to the fact that the anterior segment receives 70% of its blood supply from the anterior ciliary vessels that are embedded in the four rectus muscles. 30 Iris angiography, in humans and experimental animals, has allowed analysis of the syndrome. 41 It is evident that the simultaneous removal of three recti is especially conducive to the development of ASI because the blood supply to the anterior segment by those adjacent anterior ciliary arteries is compromised. 42 ,​ 43 Most strabismologists avoid removing three rectus muscles on the same eye during a single surgical setting, although the syndrome has also been reported to follow the removal of a third rectus muscle many months to years after the first two rectus muscles were removed. ASI has also been reported following the removal of two rectus muscles. 44 ,​ 45 Interruption of the circulation provided by the anterior ciliary vessels may occur following segmental episcleral buckling and cryopexy. 46 As expected, ASI is more common in older patients rather than young patients in whom the circulation is probably more robust.

7.3.2 Treatment of Anterior Segment Ischemia

Topical cycloplegics and topical and systemic steroids are utilized to minimize inflammation. Hyperbaric oxygen is also reported to be of value. The sequelae of ASI may include iris atrophy, corectopia, cataract, glaucoma, hypotony, and phthisis.

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