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

19.3.3 Scleral Dellen

Variation in the size of collagen bundles, random organization of collagen bundles and hydration are thought to be responsible for the sclera being opaque and white. The sclera may become translucent when it is dehydrated by 40% or more [29]. The cause of scleral dellen is thought to be related to tear film disruption, scleral dehydration, and in one case thought to be exacerbated by excessive cauterization of episcleral vessels with development of focal ischemia [30]. Perez [31] reported conservative treatment of a scleral delle using aggressive ocular lubrication and patching, which resulted in rapid resolution of the lesion within 48 h. Lee and coworkers [32] described a patient who developed a severe scleral delle following medial rectus muscle resection through a limbal incision using a bowtype adjustable suture technique and a conjunctival recession (>Fig. 19.30). They remarked that though the sclera appeared extremely thin and perforation appeared imminent, scleral dellen are actually benign lesions. Their patient was managed with

Chapter 19

lubrication and advancement of the conjunctiva. They pointed out that although scleral dellen are benign lesions, the condition must be distinguished from surgically induced necrotizing scleritis. This distinction is not generally difficult because, unlike scleral dellen, surgically induced necrotizing scleritis typically presents with pain, marked inflammation, and is typically associated with systemic immunologic disease.

19.3.4 Scleritis

Scleritis has been rarely reported following strabismus surgery. Hemady and coworkers [33] reported a case of scleritis in a 70- year-old man following inferior rectus muscle recession due to thyroid-related ophthalmopathy. Gross and coworkers [34] reported a case of necrotizing scleritis in an elderly patient who underwent surgery to treat a gaze palsy and sixth-nerve paresis following a stroke. The patient was treated with topical and systemic corticosteroids and ibuprofen, and ultimately did well.

Fig. 19.30a,b. Scleral delle noted a on the 5th postoperative day, and b 1 week after treatment. (Reprinted from [31] Journal of AAPOS, volume 6, Perez I, The “scleral dellen,” a complication of adjustable strabismus surgery, pp 332–333, 2002, with permission from American Association for Pediatric Ophthalmology and Strabismus)

19.3.5 Agyrosis

Bartley and coworkers [35] reported a patient with a pigmented scleral mass from argyrosis following strabismus surgery. The duration of the lesion was unknown and was presumed to have been due to silver nitrate collyrium instillation following strabismus surgery 67 years earlier.

19.4Anterior Segment/Intraocular Complications

Intraocular complications as a result of strabismus surgery are uncommon and are generally associated with perforation of the sclera. Rare reported complications have included hyphema (Chap. 24) and cataracts (Chap. 21). Abnormalities of the iris and pupil, including iris atrophy, corectopia and a poorly reactive pupil can occur as a result of anterior segment ischemia (Chap. 20). Postoperative mydriasis and paralysis of accommodation have been reported following surgery on the inferior oblique muscle. [36] This complication is thought to occur because of stretching of the inferior division of the oculomotor nerve as a result of excessive traction on the inferior oblique muscle during surgery. The resulting accommodative paralysis may recover with time.

References

1.Pedersen LR (1972) Corneal changes following operation for strabismus (rectus surgery) with special reference to occurrence of Dellen. Acta Ophthalmol (Copenh) 50:771–781

Ophthalmol 12:877–883

3.Mai G, Yang S (1991) Relationship between corneal dellen and tearfilm breakup time. Yan Ke Xue Bao 7:43–46

4.Tessler HH, Urist MJ (1975) Corneal dellen in the limbal approach to rectus muscle surgery. Br J Ophthalmol 59:377–379

5.Insler MS, Tauber S, Packer A (1989) Descemetocele formation in a patient with a postoperative corneal dellen. Cornea 8:129–130

6.Zehl DN, Snell AC (1977) Extraocular muscle surgery in the presence of complete paralysis of the fifth, sixth and seventh cranial nerves. J Pediatr Ophthalmol 14:76–78

7.Wintle RV, Choong YF, Laws DE (2003) Unilateral corneal anaesthesia and ulceration following squint surgery in a child with Pendred syndrome and bilateral sixth nerve palsy. Br J Ophthalmol 87:1192

8.Pons ME, Rosenberg SE (2004) Filamentary keratitis occurring after strabismus surgery. J AAPOS 8:190–191

9.Müller A, Doughty MJ, Watson L (2002) A retrospective pilot study to assess the impact of strabismus surgery on the corneal endothelium in children. Ophthalmic Physiol Opt 22:38–45

10.Hamed LM, Ellis FD, Boudreault G, Wilson FM 2nd, Helveston EM (1987) Hibiclens keratitis. Am J Ophthalmol 104:50–56

11.Apt L, Isenberg S, Yoshimori R, Paez JH (1984) Chemical preparation of the eye in ophthalmic surgery. III. Effect of povidoneiodine on the conjunctiva. Arch Ophthalmol 102:728–729

12.Biglan AW, Chang A, Hiles DA (1980) Prolapse of conjunctiva following external levator resection. Ophthalmic Surg 11:581–583

13.Malone TJ, Tse DT (1990) Surgical treatment of chemotic conjunctival prolapse following vitreoretinal surgery. Arch Ophthalmol 108:890–891

14.Schoen FJ (1994) Blood vessels, 5th edn. In: Contran RS (ed) Pathologic basis of disease. WB Saunders, Philadelphia, Pa., p 507

15.Ferry AP (1989) Pyogenic granulomas of the eye and ocular adnexa: a study of 100 cases. Trans Am Ophthalmol Soc 87:327– 343; discussion 343–347

16.Lin CJ, Liao SL, Jou JR, Kao SC, Hou PK, Chen MS (2002) Complications of motility peg placement for porous hydroxyapatite orbital implants. Br J Ophthalmol 86:394–396

17.Coats DK, McCreery KM, Plager DA, Bohra L, Kim DS, Paysse EA (2003) Nasolacrimal outflow drainage anomalies in Down’s syndrome. Ophthalmology 110:1437–1441

18.Akova YA, Demirhan B, Cakmakci S, Aydin P (1999) Pyogenic granuloma: a rare complication of silicone punctal plugs. Ophthalmic Surg Lasers 30:584–585

19.Soll SM, Lisman RD, Charles NC, Palu RN (1993) Pyogenic granuloma after transconjunctival blepharoplasty: a case report. Ophthal Plast Reconstr Surg 9:298–301.

lomas after strabismus surgery. Ophthalmology 112:1283–1286

21.Ullrich CR, Garola RE, Cibis GW (2003) Bilateral extraocular muscle epithelial inclusion cysts as a complication of strabismus surgery. J AAPOS 7:366–367

22.Kushner BJ (1992) Subconjunctival cysts as a complication of strabismus surgery. Arch Ophthalmol 110:1243–1245

23.Hawkins AS, Hamming NA (2001) Thermal cautery as a treatment for conjunctival inclusion cyst after strabismus surgery. J AAPOS 5:48–49

24.Hariprasad SM, Mieler WF, Holz ER (2002) Vitreous penetration of orally administered gatifloxacin in humans. Trans Am Ophthalmol Soc 100:153–159

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

26.Rodrigues MM, Cullen G, Shannon G (1976) Primary localized conjunctival amyloidosis following strabismus surgery. Can J Ophthalmol 11:177–179

27.Ludwig IH, Chow AY (2000) Scar remodeling after strabismus surgery. J AAPOS 4:326–333

28.Helveston EM (1993) Surgical management of strabismus: an atlas of strabismus surgery, 4th edn. Mosby-Year Book, St. Louis, Mo., p 82

29.Watson P (1995) Diseases of the sclera and episclera. Duane’s ophthalmology. Lippincott-Raven, Philadelphia, Chap. 23.1

30.Sharma P, Arya AV, Prakash P (1990) Scleral dellen in strabismus surgery. Acta Ophthalmol (Copenh) 68:493–494

31.Perez I (2002) The “scleral dellen,” a complication of adjustable strabismus surgery. J AAPOS 6:332–333

32.Lee DH, Herion MA, Unwin DR, Cruz OA (2003) Scleral dellen after bilateral adjustable suture medial rectus muscle resection. J AAPOS 7:221–222

33.Hemady R, Sainz de la Maza M, Raizman MB, Foster CS (1992) Six cases of scleritis associated with systemic infection. Am J Ophthalmol 114:55–62

34.Gross SA, von Noorden GK, Jones DB (1993) Necrotizing scleritis and transient myopia following strabismus surgery. Ophthalmic Surg 24:839–841

35.Bartley GB, Buller CR, Campbell RJ, Bullock JD (1991) Pigmented episcleral mass from argyrosis following strabismus surgery. Arch Ophthalmol 109:775–776

36.Bajart AM, Robb RM (1979). Internal ophthalmoplegia following inferior oblique myectomy: a report of three cases. Ophthalmol 86;1401-6.

20.1 Blood Supply of the Anterior Segment

The blood supply to the anterior segment is derived from the long posterior ciliary arteries, the anterior ciliary arteries, and the conjunctival arteries (>Fig. 20.1). The anterior ciliary arteries are thought to provide approximately 70% of the blood supply to the anterior segment with the long posterior ciliary arteries supplying most of the remainder, and the conjunctival arteries supplying a minor component of the blood supply to this region of the eye [1].

The conjunctival arteries are derived from the palpebral branches of the nasal and lacrimal arteries of the lid (posterior conjunctival arteries) and the anterior ciliary arteries (anterior conjunctival arteries). The anterior ciliary arteries are derived from the ophthalmic artery where they begin as the muscular arteries that supply the rectus muscles before dividing into the anterior ciliary arteries. The anterior ciliary arteries travel along the tendons of the rectus muscles and give off anterior conjunctival arteries just before piercing the sclera. The superior, medial, and inferior rectus muscles each carry two anterior ciliary arteries, while the lateral rectus muscle generally carries only one (>Fig. 20.2). The oblique muscles do not carry an anterior ciliary artery and therefore do not contribute to the anterior segment circulation.

The conjunctival and anterior ciliary arteries join to form an episcleral plexus at the limbus. There is free anastomosis between the subconjunctival and episcleral tissue in the region of this plexus between the anterior conjunctival arteries and the terminal branches of the posterior conjunctival arteries. Branches of the anterior ciliary arteries supply the ciliary muscle, the iris and the anterior portion of the choroid. Branches

of the anterior ciliary artery also join with branches of the long posterior ciliary arteries to supply the ciliary body and the major arterial circle of the iris. The latter carries blood to the ciliary body, the ciliary processes and the iris.

20.2 Incidence

Severe anterior segment ischemia is a rare but potentially sight-threatening complication following strabismus surgery. The incidence of anterior segment ischemia is unknown but a survey of pediatric ophthalmologists published in 1986 estimated that significant anterior segment ischemia occurred in approximately 1 in 13,000 cases [2]. This reported incidence probably underestimates its true occurrence, as mild cases of anterior segment ischemia almost certainly occur without clinical detection. The low incidence of clinically significant anterior segment ischemia probably reflects the protection offered by the rich collateral blood supply from both the long posterior ciliary and anterior ciliary arteries that continue to supply blood to the anterior segment when the anterior ciliary and conjunctival arteries are disrupted. The blood supplied by the posterior ciliary arteries, however, is probably not a significant factor, as evidenced by the fact that anterior segment ischemia does not occur with occlusion of only the posterior ciliary arteries [3]. Therefore, it appears that surgery of the extraocular muscles, specifically the rectus muscles, leads to anterior segment ischemia in at-risk patients, by alteration of the anterior segment circulation through disruption of the anterior ciliary arteries.

Disinsertion of a single vertical rectus muscle will result in hypoperfusion to the region of the anterior segment adjacent to the detached muscle. Hypoperfusion can be demonstrated using iris angiography [3–5] (>Fig. 20.3). Hypoperfusion defects

Fig. 20.3. Iris hypoperfusion as demonstrated by iris angiography (Courtesy of Richard A. Saunders, MD)

Chapter 20

that occur following vertical rectus muscle disinsertion are generally larger than those following horizontal rectus muscle disinsertion. The anterior ciliary arteries that travel with the vertical rectus muscles supply the majority of the inferior and superior portions of the iris and they have limited collateral connection to the posterior ciliary arteries. Infants and young children do not usually show signs of hypoperfusion following vertical rectus muscle disinsertion. The area of hypoperfusion will decrease with time following redistribution of blood flow from the long posterior ciliary arteries and increase in the capacity of the collateral circulation. An anterior ciliary artery that has been detached from the globe does not reestablish a direct communication with the distal aspect of the vessel [6]. The circulation that is reestablished to the anterior segment is not equivalent to that which was present prior to disruption of the vessel, leaving the patient with a net loss of blood flow to the anterior segment even after maximum collateral circulation has been established. This is important to keep in mind when planning surgery on patients who have had previous strabismus surgery.

20.3 Risk Factors and Prevention

Predicting which patients may be at risk for anterior segment ischemia can be difficult. 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 (>Table 20.1). Of these risk factors, advanced age appears to be the most important [2]. Clinically, significant anterior segment ischemia has been reported very rarely in children undergoing strabismus surgery [2, 7]. Anterior segment ischemia has been reported following detachment of only two rectus muscles in older patients and in patients with other concurrent risk factors. Despite anecdotal reports that all four rectus muscles can be detached in children without development of anterior segment ischemia, we always attempt to spare the anterior ciliary circulation associated with at least one rectus muscle. We are not only concerned about the possibility of acute development of anterior segment ischemia following surgery on all four rectus muscles, but also of potential future circulatory issues involving the anterior segment.

Advanced age

Previous rectus muscles surgery

History of vasculopathies (i.e., diabetes and hypertension ) Simultaneous surgery on multiple muscles in the same eye Simultaneous surgery on adjacent rectus muscles

Surgery on vertical rectus muscles Use of a limbal incision

The number of rectus muscles and type (vertical versus horizontal) operated on is another important risk factor anterior segment ischemia. Surgery on a single vertical

in a patient with other risk factors can lead to significant perfusion defects that are detectable with iris angiography in rare cases to clinically significant anterior segment Simultaneous surgery on both vertical rectus muscles

a higher risk of anterior segment ischemia than simultaneous surgery on the horizontal rectus muscles due to the smaller contribution of the long posterior ciliary arteries to blood flow in the superior and inferior aspects of the anterior segment. Surgery on an adjacent vertical and horizontal rectus muscle is also more likely to lead to an observable negative 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.

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. As noted earlier, 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 (advanced age and previous strabismus surgery) 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. Surgical strategies designed to reduce the risk of anterior segment ischemia in patients at greater risk should be considered when possible, as reviewed below.

Fig. 20.4. Striate keratopathy seen in grade 4 anterior segment is­ chemia. (Courtesy of Richard A. Saunders, MD)

sion. Corneal findings in grade 4 anterior segment ischemia include striate keratopathy and corneal edema. The corneal signs may be associated with hypotony, cataract formation and development of a maculopathy. Grade 4 anterior segment is­ chemia can result in loss of vision and even phthisis bulbi in rare cases [9]. Patients with grade 3 or grade 4 anterior segment ischemia may complain of pain and decreased vision, with onset typically 1 or 2 days following surgery. In most cases, improvement will occur in the weeks following surgery. If significant iris ischemia develops, iris atrophy, corectopia and a poorly reactive pupil may remain permanently.

20.4 Signs and Symptoms

Anterior segment ischemia can range from mild and selflimiting to severe and vision threatening. Anterior segment ischemia has been classified into four grades of severity as by Lee and Olver [8] (>Table 20.2). Grade 1 is characterized by reduced iris perfusion that may be demonstrated with iris angiography. Grade 2 is characterized by the presence of pupillary abnormalities such as an ectopic or poorly reactive pupil in the areas of iris hypoperfusion. Grade 3 anterior segment ischemia includes the aforementioned abnormalities and the presence of postoperative uveitis, while grade 4 includes keratopathy that can range from mild to severe. The cornea may develop subtle posterior folds or frank edema (>Fig. 20.4). Grades 1–3 may lead to permanent pupil changes, but do not lead to loss of vi-

20.5 Treatment

There is no universally agreed upon protocol for treatment of anterior segment ischemia [2]. 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. The use of hyperbaric oxygen was reported by de Smet and co-workers [10] in a patient in whom the use of corticosteroids was contraindicated. This 62-year-old man with thyroid-related eye disease developed anterior segment ischemia after two-muscle adjustable suture surgery of a vertical deviation. He was treated with hyperbaric oxygen and the acute symptoms almost completely resolved in 3 days. Because most patients who develop signs of anterior segment ischemia

will experience resolution with time, it is difficult to know what role hyperbaric oxygen or other therapies played in the good outcomes reported in such case reports. Animal studies have shown that the use of prostaglandin synthetase inhibitors, such as diclofenac sodium, may have a role in the prevention and/or treatment of anterior segment ischemia [11]. There are no data to suggest that any specific treatment of anterior segment ischemia improves the outcome of this disorder.

20.6Prevention of Anterior Segment Ischemia

The best treatment for anterior segment ischemia is obviously prevention. When possible, a surgical plan for at-risk patients should be designed that will minimize the risk that clinically significant anterior segment ischemia will develop (>Table 20.3). Potential strategies include limiting the number of rectus muscles that are detached from the globe, techniques to preserve anterior ciliary arteries, if possible, and staging surgical procedures, when needed. Each of these strategies are reviewed below.

20.7Mitigating Risk Through Surgical Planning

20.7.1 Conjunctival incision

Limbal conjunctival incisions disrupt the perilimbal conjunc- tival-Tenon’s circulation. This circulation, though its contribution to anterior segment circulation is modest at best, may provide some protection against development of anterior segment ischemia. Fornix-based incisions result in less disruption to the perilimbal circulation and have been shown to be associated with fewer ischemic changes following threeor fourrectus tenotomies in an animal model [12]. The use of a fornix conjunctival incision might be considered when planning strabismus surgery on patients who are at risk for anterior segment ischemia. The advanced age of patients who are at highest risk for developing anterior segment ischemia, unfortunately, may make the use of a fornix incision difficult with many patients, because of the fragile conjunctiva that is often present in these

Limit the number of rectus muscles that are detached from the globe

Preservation of anterior ciliary arteries Staging surgical procedures Utilization of a fornix incision

Nonstandard techniques, such as mechanical fixation of the globe

Chapter 20

20.7.2Minimizing Number

of Muscles Operated in an Eye

When possible, simultaneous surgery on three rectus muscles in the same eye should be avoided and surgery on all four rectus muscles should only be considered in extremely rare cases when there are no other risk factors for anterior segment ischemia and no other alternatives are available. We have not operated all four rectus muscles simultaneously in an eye and do not advocate doing so. When operating the fourth rectus muscle of a patient who has had previous strabismus surgery or a second or third muscle in a patient who we believe is likely to require more surgery in the future, we will attempt to spare the remaining anterior ciliary arteries by using vessel-sparing techniques for recession surgery and tucks instead of resection surgery.

When treatment for a concurrent vertical and horizontal deviation requires surgery on three rectus muscles, consideration should be given to performing surgery on both eyes, if possible. If it is not desirable to perform surgery on both eyes (i.e., due to unilateral vision impairment, patient choice, etc.) consideration should be given to correction of only one component of the deviation. Prism can be attempted for the residual deviation and/or surgery can be offered for the remaining deviation after several months have passed and collateral circulation has developed.

Alternative surgical procedures can also be considered. We have used anterior transposition of the inferior oblique mus­ cle in selected cases where a horizontal and vertical deviation requires treatment in a poorly seeing eye [13]. For example, we treated a patient with dense amblyopia who had both a large exotropia and a large hypertropia. A horizontal recession/resection procedure was performed to treat the exotropia. The hypertropia was treated with an anterior transposition of the inferior oblique muscle. The patient’s eyes appeared straight following surgery. The elevation deficit caused by the unilateral inferior oblique procedure was not bothersome to the patient and allowed the vertical deviation to be treated without detaching a third rectus muscle or operating the sound eye.

Surgical treatment of paralytic strabismus is probably the most common scenario in which the strabismus surgeon may need to operate on three rectus muscles in an eye simultaneously. Typically, there is a need to perform a transposition procedure to the paralytic muscle, combined with a weakening procedure of the antagonist muscle. In such cases, the surgeon may be able to avoid the need to surgically weaken the antagonist muscle by injecting botulinum toxin into the antagonist. Alternatively, the use of posterior fixation augmentation sutures as described by Foster [14] (Chap. 13) or simultaneous

the transposed muscles as described by Brooks et

. 13) may eliminate the need for either botulinum surgery on a third rectus muscle. It should be noted toxin may not be as effective as surgical weaken­ antagonist in cases where the antagonist muscle has significantly contracted over time. These measures are protective and anterior segment ischemia has been even when transposition procedures have been comthe use of botulinum toxin treatment to the antago-

nist rectus muscle and following posterior fixation suture augmentation of a transposition procedure [16, 17].

20.7.3 Sparing of the Anterior Ciliary Arteries

When surgical correction of strabismus requires operation on multiple rectus muscles, or on the third or fourth muscle of a patient who has undergone previous rectus muscle surgery and who is at risk for anterior segment ischemia, a potentially useful approach is surgical sparing of the anterior ciliary arteries. The anterior ciliary arteries are branches of the ophthalmic artery. They course internal to the rectus muscle and exit the muscle belly before the muscle becomes tendinous. They then travel along the external or orbital surface of the rectus muscles

before dividing into multiple branches posterior to the muscle insertion. Sparing of one or more anterior ciliary arteries can be accomplished through the use of a muscle splitting procedure, a muscle union procedure, a muscle tucking procedure or by dissecting the ciliary arteries from the muscle (>Fig. 20.5). A partial muscle transposition procedure can be utilized in which the surgeon carefully divides the target muscles, transposing only 50%–80% of the muscle, taking care to leave one anterior ciliary artery from each muscle intact. Coats and coworkers [18] reported successful use of split rectus muscle procedures to treat paralytic strabismus (Chap. 13). If needed at the time of a partial tendon transposition procedure, recession of a third rectus muscle can be done while still only disrupting a minimum number of anterior ciliary arteries.

When attempting to spare anterior ciliary vessels in a patient undergoing a split rectus muscle transposition pro-

cedure, it is important to evaluate the course of the anterior ciliary arteries on the orbital surface of the muscle/tendon. The arteries often have an irregular and unpredictable course along the muscle. Both arteries are sometimes found on the same side of the muscle, and the arteries can cross from one side of the muscle to the other (>Fig. 20.6). Determining how to best create a longitudinal split in the muscle to preserve the desired artery requires careful consideration of this anatomy followed by careful planning and execution. A Jensen procedure (Chap. 13) is another reasonable alternative to procedures that result in severing of the anterior ciliary arteries when the effect of a transposition procedure is needed. Theoretically, this allows the surgeon to perform a transposition procedure without detaching any of the rectus muscles. However, we believe that suture placement around the rectus muscles during a Jensen procedure results in significant compromise, and usually obliteration, of the circulation in the involved rectus muscles through strangulation of the vessels by the Jensen suture. Anterior segment ischemia has been reported following the Jensen procedure, including one case involving a 10-year-old child [19, 20]. In an effort to minimize disruption of the anterior ciliary arteries following a Jensen procedure, Coats has advocated passing the Jensen suture beneath the anterior ciliary arteries so that only the involved muscles are incorporated in the suture [21] (Chap 13).

McKeown has described a surgical technique in which the anterior ciliary arteries are dissected off the surface of the rectus muscle to avoid disruption of the associated anterior ciliary blood flow [22] (>Fig. 20.7). The anterior ciliary arteries are first dissected from the muscle (>Fig. 20.7). Suture is then placed in the muscle near the insertion of the muscle into the sclera and the muscle is then recessed with the anterior ciliary arteries still intact (>Fig. 20.7). Animal studies have demonstrated the sparing of the anterior ciliary artery circulation when multiple rectus muscles are detached from the globe using this technique [23]. The procedure is technically challenging. The technique is not failsafe, and anterior segment ischemia has been reported following strabismus surgery using this technique [24].

Wright has described a modified rectus muscle tucking procedure that appears to preserve the anterior ciliary blood flow, at least in an animal model [24] (>Fig. 20.8). The utility of this procedure in human patients has not been demonstrated, but seems logical. This use of this technique when a rectus muscle resection is needed may be considered when the risk of anterior segment ischemia is thought to be significant.

Fig. 20.6. The course of the anterior ciliary arteries along the rectus muscles and tendons is highly variable

Fig. 20.7. After dissection of the anterior ciliary arteries from the muscle, the muscle can be recessed, resected, or transposed, leaving the anterior ciliary arteries intact

20.7.4 Mechanical Fixation of the Globe

The use of nonstandard techniques such as mechanical fixation of the globe in the primary position using a variety of fixation means is another alternative to achieving alignment of the eyes in the primary position without the need to significantly disrupt the anterior segment circulation. A technique involving the use of periosteum to mechanically fixate the globe in the primary position is described in Chap. 15.

Fig. 20.8. Modified rectus muscle tuck. Note that the anterior ciliary arteries are left undisturbed

20.7.5 Staging of Surgery

Blood flow to the anterior segment improves over time in most patients following strabismus surgery on the rectus muscles, therefore many surgeons advocate staging surgical procedures when multiple rectus muscles must be operated in the same eye. This approach appears to have value [25]. The amount of time required for collateral circulation to develop following strabismus surgery is unknown, but a few clues are available. Olver and Lee [25] showed that iris circulation recovered within the first 2 weeks following surgery in most patients who did not develop anterior segment ischemia. In patients with grade 3 anterior segment ischemia, blood flow to the iris may not recover for as long as 12 weeks [26]. It is important to reemphasize, however, that the blood flow that is reestablished is inferior to that which was present before surgery. Staging of procedures probably reduces, but does not completely eliminate, the risk of anterior segment ischemia and the condition has been reported in patients undergoing strabismus surgery many years after their initial strabismus operations [26]. Nevertheless, we believe that it is prudent to stage surgery in susceptible patients when surgery is required on more than two rectus muscles in the same eye. Empirically, we wait at least 4 months between operations in this setting, assuming that the patient shows no evidence of anterior segment ischemia after their initial surgery.

20.8 Summary and Recommendations

It is impossible to predict with certainty which patients will develop anterior segment ischemia following strabismus surgery. Each patient should be evaluated for the presence of known risk factors. When possible, surgical planning should include a strategy to reduce this risk. Patients at significant risk for anterior segment ischemia should be counseled prior to surgery and monitored for the condition after surgery.

References

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10.de Smet MD, Carruthers J, Lepawsky M (1987) Anterior segment ischemia treated with hyperbaric oxygen. Can J Ophthalmol 22:381–383

11.Ino-ue M, Shirabe H, Yamamoto M (1999) Blood-aqueous barrier disruption in experimental anterior segment ischemia in rabbit eyes. Ophthalmic Res 31:213–219

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13.Parvataneni M, Olitsky SE (2005) Unilateral anterior transposition and resection of the inferior oblique muscle for the treatment of hypertropia. J Pediatr Ophthalmol Strabismus 42:163–165

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

15.Brooks SE, Olitsky SE, de BRG (2000) Augmented Hummelsheim procedure for paralytic strabismus. J Pediatr Ophthalmol Strabismus 37:189–195; quiz 226–227

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17.Murdock TJ, Kushner BJ (2001) Anterior segment ischemia after surgery on 2 vertical rectus muscles augmented with lateral fixation sutures. J AAPOS 5:323–324

18.Coats DK, Brady-McCreery KM, Paysse EA (2001) Split rectus muscle modified Foster procedure for paralytic strabismus: a report of 5 cases. Binocul Vis Strabismus Q 16:281–284

19.von Noorden GK (1976) Anterior segment ischemia following the Jensen procedure. Arch Ophthalmol 94:845–847

20.Bleik JH, Cherfan GM (1995) Anterior segment ischemia after the Jensen procedure in a 10-year-old patient. Am J Ophthalmol 119:524–525

21.Kushner BJ, Coats DK, Kodsi SR et al (2002) Grand rounds #68: a case of consecutive exotropia after recession of all four horizontal rectus muscles for the treatment of nystagmus. Binocul Vis Strabismus Q 17:304–311

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cession of various recti. An experimental study. Ophthalmology 94:1258–1271

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5.Hayreh SS, Scott WE (1978) Fluorescein iris angiography. II. Disturbances in iris circulation following strabismus operation on the various recti. Arch Ophthalmol 96:1390–1400

anterior segment circulation in monkeys. J Pediatr Ophthalmol Strabismus 28:77–81

25.Olver JM, Lee JP (1992) Recovery of anterior segment circulation after strabismus surgery in adult patients. Ophthalmology 99:305–315

26.Saunders RA, Sandall GS (1982) Anterior segment ischemia syndrome following rectus muscle transposition. Am J Ophthalmol 93:34–38

Scleral perforation is a known and potentially serious complication of strabismus surgery. It can occur at any time during surgery, but most commonly occurs during reattachment of the muscle to the sclera using sutures. The definition a perfora­ tion and a penetration depends upon the tissue of reference. By definition, a penetrating injury extends only partially through the tissue of reference while a perforation extends through the full thickness of the tissue of reference (>Fig. 21.1). Thus a scleral perforation extends full thickness through the sclera. If the eye wall (including the sclera, choroid, and retina) is the tissue of reference, then a scleral perforation represents only an eye wall penetration. Perforation of the eye wall, therefore, requires passage of a needle through all of the tissues that

constitute the eye wall. Penetration of the sclera occurs in the normal course of strabismus surgery, while perforation of the sclera represents a complication. There is an unsubstantiated, but probably accurate, perception that the incidence of scleral perforation has declined since the evolution of spatula needles in the 1970s. Sprunger and coworkers [1] pointed out that the use of magnification during strabismus surgery has also probably contributed to a decline in the rate of scleral perforation.

The reported incidence of scleral perforation varies widely. Simon and coworkers [2] sent questionnaires to 342 members of the American Association for Pediatric Ophthalmology and Strabismus. Scleral perforation, defined in their study as known retinal damage (and therefore requiring full thickness violation

Fig. 21.1. The tissue of reference is important in differentiating a scleral perforation from a scleral penetration. A penetration occurs during the normal course of strabismus surgery and extends only partially

through the sclera, while a perforation extends full thickness through the sclera