An Overview of Strabismus Surgical Procedures

Rudolph S. Wagner, MD

Weakening Procedures of the Rectus Muscles

Recession of the rectus muscles is a common strabismus surgical procedure. This procedure involves removal and reattachment of a muscle on the globe so that its new insertion is closer to the muscle origin, usually posterior to the original insertion. Absorbable sutures are placed at a predetermined point in the sclera measured with a caliper, or are allowed to hang back from a measured point and are tied at the original insertion (Slide 1, Slide 2, and Slide 3). Additional weakening procedures include a marginal myotomy, in which a full-thickness incision is made through one edge of a muscle and extended about one-third of the way across the width. This procedure may be useful when a muscle has been maximally recessed, as it provides a minimal weakening effect. Injection of purified botulinum toxin A directly into an extraocular muscle (usually intraoperatively under anesthesia in children) also provides a temporary weakening effect of an extraocular muscle (see the tutorial: An Update on the Use of Botulinum Toxin Type A for Strabismus).¹ This effect can be used to the surgeon’s advantage when combined with strabismus surgery as in extraocular muscle palsies.²

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A posterior fixation suture (faden operation or faden suture) attaches a rectus muscle to the sclera 10 mm to 18 mm posterior to the insertion using a nonabsorbable suture. This procedure can weaken a muscle primarily in its field of action without changing the primary position of the eye and can be used in conjunction with a recession. Some possible uses for this procedure include the treatment of dissociated vertical deviation, nystagmus, high accommodative convergence to accommodation esotropia, and as a weakening procedure of a yoke muscle in cases of paralytic or restrictive strabismus.

Strengthening Procedures of the Rectus Muscles

Rectus muscles are strengthened by shortening or resecting a portion of a muscle or, in cases of reoperations, by advancing a muscle closer to its original insertion. In a rectus muscle resection, a predetermined length of muscle is excised following preplacement of locked absorbable sutures (Slide 4, Slide 5, Slide 6, Slide 7). The remaining muscle is usually advanced to the original insertion or another intraoperatively determined site. Many techniques for suture placement in the muscle to be resected have been proposed. Some surgeons prefer to use a resection clamp to secure the muscle. A single double-armed suture can be used effectively in resections. The suture is locked on both margins posterior to the resection point before cutting the muscle. Care must be taken to avoid cutting the sutures, and direct visualization of the muscle and sutures is essential. Resections of the medial rectus muscles, particularly in restricted muscles as found in reoperations, can be difficult. Often, a second muscle hook can be used to expose the muscle.

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In cases of overcorrection where a muscle has been recessed, the muscle can be advanced to the original insertion. In these instances, knowledge of the average distances of the insertion site from the limbus is important for making intraoperative decisions as to muscle placement (see the tutorial: Strabismus Surgery Basics). In resections and advancements, care must be taken to avoid advancing the conjunctiva and, in medial rectus muscle surgery, the plica and semilunar fold too close to the limbus. This results in a poor cosmetic appearance and can produce corneal dellen if the tissue near the limbus is left elevated. It is difficult to adjust a resected muscle postoperatively, although some surgeons do.

Superior Oblique Tendon Surgery

In extraocular muscle surgery, superior oblique muscle/tendon surgery is performed less frequently than other procedures. Strabismus resulting from superior oblique muscle or trochlear nerve dysfunction is less common than other forms of strabismus. Superior oblique tendon surgery is not predictable because amounts of surgery in some procedures like tucking are based on intraoperative findings such as tendon laxity and previous surgical experience.

Folding or tucking strengthens the superior oblique tendon. Many approaches and techniques are available, which is beneficial when underaction of the superior oblique muscle occurs as in recently acquired superior oblique muscle palsies. The posterior fibers of the tendon are responsible for vertical movement, whereas the anterior fibers are responsible for torsional eye movements. In cases where correction of excyclotorsion is the primary objective as in bilateral superior oblique muscle palsies, temporal advancement of the anterior half of the tendon produces satisfactory results. This technique, called the Harada-Ito procedure, is performed as an adjustable procedure in older patients.³ All procedures that tuck or strengthen the superior oblique tendon may produce a Brown syndrome. The superior oblique tendon is advanced to a position proximal to the medial rectus muscle insertion in case of oculomotor nerve palsy, which results in adduction force.

Weakening of the superior oblique muscle is usually accomplished by performing a tenectomy or tenotomy. Superior oblique tendon expansion, using a silicone retinal band or a nonabsorbable suture material, is an effective way to weaken the superior oblique tendon without producing the signs of a superior oblique palsy.^4,5 This technique is used effectively in Brown’s syndrome and in A pattern strabismus. Postoperative extrusion of the implant occasionally occurs.

Inferior Oblique Muscle Surgery

Surgery on the inferior oblique muscle is performed frequently. The high incidence of V pattern strabismus with overacting inferior oblique muscles accounts for this high frequency. Weakening the antagonist inferior oblique muscle in a case of superior oblique muscle palsy is a popular procedure among surgeons. Basic techniques to weaken the inferior oblique muscle include myotomy, myectomy, and recession. These procedures are best performed under direct visualization to avoid complications resulting from incomplete muscle surgery or adherence from prolapsed adipose tissue following disruption of Tenon’s capsule.

The 14-mm recession popularized by Parks uses the inferior temporal vortex vein as a marker for suture placement for reattachment of the inferior oblique tendon to the sclera.⁶ The inferior oblique muscle, its vascular bundle, and the branch of the oculomotor nerve providing the innervation may be removed in the area where Tenon’s capsule is penetrated for maximum weakening. This technique is called denervation and extirpation.

Many surgeons prefer to weaken the inferior oblique muscle by advancing the tendon near the lateral margin of the inferior rectus muscle tendon. This procedure is useful in reducing overaction of the inferior oblique muscle and can also treat concurrent dissociated vertical deviation.⁷ Advancing the inferior oblique tendon effectively converts the muscle to a depressor of the globe. The placement of the tendon behind or anterior to the insertion of the inferior rectus muscle is used for grading the amount of effect desired. Lateral displacement of the inferior oblique tendon can result in unwanted depression of the globe in abduction, which limits elevation of the eye in abduction and mimics overaction of the inferior oblique muscle. This “anti-elevation syndrome” is best avoided by positioning the advanced inferior oblique tendon close to the lateral margin of the inferior rectus muscle.⁸

Tendon Transposition Procedures

Transposition of portions of partial or complete rectus muscle tendons is done to improve ductions in the field of action of an absent or paretic muscle. Recently, augmentation of transposition procedures has been reported with excellent results. Foster⁹ described total tendon transfer adjacent to the insertion of the paretic muscle. In addition, Foster advocates placing a posterior fixation suture on each transposed rectus muscle approximately 8 mm posterior to the insertion of the paretic muscle, fixing the belly of each transposed muscle adjacent to the border of the paretic muscle. In an attempt to reduce the possibility of the development of anterior segment ischemia, splitting of the rectus muscles is performed and only one half of the tendon transposed for each muscle. The Hummelsheim procedure can be augmented by resecting 4 mm to 8 mm of the muscles to be transposed (see the tutorial: Augmented Hummelsheim Procedure for Paralytic Strabismus).¹⁰ Transpositions are combined with recessions of the antagonist muscle or with botulinum chemo-denervation (see the tutorial: An Update on the Use of Botulinum Toxin Type A for Strabismus).

Grading Millimeters for Strabismus Surgery

Individual surgeon preferences determine the muscles to be operated on as well as the amount of a graded recession or resection. Some surgeons prefer to measure posterior from the original muscle insertion when performing a recession, whereas others measure from the limbus because individual anatomic variation exists in distances from the limbus to the insertion. This may be obvious in infants and young children, where the insertions are closer and the globe smaller than in adults. Despite the measurement a surgeon uses, consistency is important so that surgical results will be reproducible. Experienced surgeons establish their own tables for the amount they will recess or resect a muscle for a certain measured deviation and are ready to modify their procedure when faced with unexpected intraoperative findings.¹¹

For vertical rectus muscles, 1 mm of recession or resection will correct approximately 2 to 3 PD of deviation. For horizontal deviations, no true linear relationship exists, and tables have been formulated to provide initial guidelines. Tables 1 to 7 are useful for initial surgical planning.

References

1. Scott AB, Magoon EH, McNeer KW, et al. Botulinum treatment of strabismus in children. Trans Am Ophthalmol Soc. 1989; 87:174-184.
2. Rosenbaum AL, Kushner BJ, Kirschen D. Vertical rectus muscle transposition and botulinum toxin to medial rectus for abducens palsy. Arch Ophthalmol. 1989; 107:820-831.


3. Harada M, Ito Y. Surgical correction of cyclotropia. Jpn J Ophthalmol. 1964; 8:88-93.


4. Wright KW. Superior oblique silicone expander for Brown’s syndrome and superior oblique overaction. J Pediatr Ophthalmol Strabismus. 1991; 28:101-107.


5. Suh DW, Guyton DL, Hunter DG. An adjustable superior oblique tendon spacer with use of nonabsorbable suture. J AAPOS. 2001; 5:164-171.


6. Stager DR, Parks MM. Inferior oblique weakening procedures. Effect on primary position horizontal alignment. Arch Ophthalmol. 1973; 90:15-16.


7. Elliott RL, Nankin SJ. Anterior transposition of the inferior oblique. J Pediatr Ophthalmol Strabismus. 1981; 18:35.


8. Kushner BJ. Restriction of elevation in abduction after inferior oblique anteriorization. J AAPOS. 1997; 1:55-62.


9. Foster RS. Vertical muscle transposition augmented with lateral fixation. J AAPOS. 1997; 1:20-30.


10. Brooks SE, Olitsky SE, deB Ribeiro G. Augmented Hummelsheim procedure for paralytic strabismus. J Pediatr Ophthalmol Strabismus. 2000; 37:189-195.


11. Wagner RS. Surgical management of strabismus. In: Nelson LB, Olitsky SE, eds. Harley’s Pediatric Ophthalmology. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2005:193-200.