Chapter 86 Strabismus surgery complications and how to avoid them

Severe complications of strabismus surgery are rare but they can be devastating. This chapter will discuss the frequency and management of problems our patients may encounter after surgery and how we might approach consenting patients to ensure their expectations are well informed.

Incidence

The incidence and outcomes described are from a 2-year prospective survey of severe complications of strabismus surgery carried out by the author through the British Ophthalmic Surveillance Unit (BOSU) and the available literature. The incidence of severe complications of strabismus surgery was 2.5–3 per 1000. Globe perforation is the most common complication with almost an incidence of 1 : 1000. Retinal detachment and endophthalmitis are the least common reported (Fig. 86.1, Box 86.1 and Table 86.1). Anterior segment ischemia was not part of the BOSU study, but may be 1 : 13 000 operations.¹ Eighteen percent of patients with a complication had a poor or very poor outcome: about 0.05% or 1 : 2000 of patients operated on.

Fig. 86.1 Incidence of severe complications of surgery, per 10 000 operations. RD = retinal detachment.

Box 86.1

Classification of outcome

Grade 1: Good outcome

Grade 2: Surgical or medical intervention but good outcome

Grade 3: Surgical or medical intervention asymptomatic but compromised outcome

Grade 4: Surgical or medical intervention but poor outcome, e.g. double vision or up to 2 lines of loss of vision on a Snellen chart

Grade 5: Very poor outcome, greater than 2 lines of visual loss on a Snellen chart

Table 86.1 Number of complications reported in BOSU study. The p value compares adult and child rates for each complication

Mild complications (Box 86.2)

We devised a 5 point scale depending on the severity of outcome of the complication. This is outlined in Figure 4. The number of complications in the 5 categories split into adults and children is shown in Figure 5 with the p values. Although there were more infections and globe perforations in children and more SINS and lost muscle in adults only SINS reached statistical significance.

When we look at outcome, 18% of patients with a complication had a poor or very poor outcome. This means about 0.05% or 1:2000 of patients operated on had a poor or very poor outcome.

Dellen

Dellen tend to occur in the peripheral cornea, specifically nasal and temporal quadrants in the first 1–2 weeks following strabismus surgery. Dellen are thinning of the cornea due to the drying out of the collagen in the stroma related to poor corneal wetting. They are related to tear film disruption and altered anterior segment contour due to swollen conjunctiva which prevents the smooth travel of the eyelids. They are more common in adults, but may occur in children (who are rarely examined on the slit-lamp). The reported the incidence is between 0.3% and 22.45%.² It is usually self-limiting or responds to topical lubricants; rarely a contact lens is required.

Box 86.2

Mild complications of strabismus surgery

Dellen

Chronic red eye

Pyogenic granuloma

Tenon’s fascia prolapse

Epithelial inclusion cyst

Chemosis

Chronic red eye

Redness is common, especially after repeated strabismus surgery, but some patients have a persistent red eye for many weeks or months. These patients are unhappy, feeling their appearance is harmed. Some of this may be related to more long term problem with corneal wetting and responds to topical lubricants. Prolonged postoperative inflammation or violation of the orbital fat may contribute to a chronic red eye, most often of the medial rectus and surrounding tissue. Prevention includes meticulous surgery, hemostasis, avoidance of orbital fat, and thinning and reduction of thickened and redundant medial conjunctiva. This often occurs in adults with long standing (especially consecutive) exotropias. We give such patients intensive topical steroid drops for a month following strabismus surgery; occasionally, long term lubricants and topical steroids are required. If the eye is still red after 3 months, we may give subconjunctival depot steroids to whiten the eye, and reduce the conjunctival bulk.

Pyogenic granuloma

This fleshy mass appears a few weeks after surgery and is composed of inflammatory cells and capillary proliferation. It may be confused with a suture granuloma. They respond to topical steroids but occasionally require surgery.

Prolapsed Tenon’s capsule

This occurs in children and young adults with a prominent Tenon’s layer. It is caused by poor conjunctival closure. If the prolapse is large, it may need to be trimmed, but it usually resolves spontaneously.

Epithelial inclusion cyst (Fig. 86.2)

This rare complication is caused by deposition of conjunctival epithelial cells into deeper tissues. Most are small, some can be large, especially those at muscle insertions. They enlarge and need surgical removal.

Fig. 86.2 Conjunctival epithelial inclusion cysts. (A) Cyst over medial rectus. (B) Cyst over inferior rectus. (C) Cyst over inferior rectus following excision.

(Courtesy of Mr Robert Morris.)

Chemosis

Chemosis occurs after most strabismus surgery. It is rarely severe, but it can be so severe that the conjunctiva is exposed and the chemosis is exacerbated by drying: intensive topical lubricants and steroids usually resolve it. Rarely, it may be necessary to tape the lid shut or perform a temporary “superglue” tarsorrhaphy (with caution in children because of distress and amblyopia risk). An option is to suture the conjunctiva into the fornices.

Severe complications (Box 86.3)

Anterior segment ischemia (Fig. 86.3)

Two anterior ciliary arteries (branches of the ophthalmic artery) supply each rectus muscle apart from the lateral rectus which has only one: the obliques have no anterior ciliary arteries.

Fig. 86.3 Anterior segment ischemia. (A) Severe ischemia causing corneal edema. (B) Same eye 6 months later; note mid-dilated pupil. (C) Anterior lens opacities following anterior segment ischemia. (D) Iris atrophy following anterior segment ischemia.

(Courtesy of Mr Robert Morris.)

Box 86.3

Severe complications of strabismus surgery

Globe perforation

Orbital infection

Endophthalmitis

Surgically induced necrotizing scleritis

Anterior segment ischemia

The incidence of significant anterior segment ischemia (ASI) may be 1 : 13 000 cases.¹ It was not surveyed in the BOSU study because ASI would be grossly underreported, especially in children where postoperative slit-lamp examination is not normally performed. Severe outcomes are rare although there is a report of phthisis bulbi.¹ Risks factors for ASI include increasing age, previous rectus surgery, operations on multiple muscles (especially recti) in the same eye, circulation problems (i.e. hypertension or diabetes), similar surgery on adjacent rectus muscles, surgery on vertical rectus muscles, and a limbal incision.

In children, it may be safe to operate on more than two recti muscles at once: most surgeons avoid operating on all four recti muscles simultaneously. If it is necessary to operate on more than two recti muscles in an adult or if the patient has a very high risk of developing ASI, anterior ciliary artery sparing surgery can be performed by dissecting out the anterior ciliary arteries from the muscle or performing a partial tendon transposition, sparing at least one of the anterior ciliary arteries.

Symptoms and signs of ASI can vary from mild uveitis and reduced iris perfusion to a keratopathy ^1,³ (Table 86.2).

Grade 1 ASI can only be detected by iris angiography.

Grade 2 ASI is caused by areas of iris hypoperfusion, sometimes an abnormally shaped pupil. It rarely requires treatment.

Grades 3 and 4 ASI usually require treatment with topical or systemic corticosteroids. Unusual treatments include hyperbaric oxygen. The vast majority recover with only minor sequelae including iris atrophy, corectopia, or a poorly reacting pupil.