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27.Where is the causative lesion?

The lesion is in the medial longitudinal fasciculus. Causes include multiple sclerosis, ischemic vascular disease, brain-stem tumor, and trauma.

Bibliography

American Academy of Ophthalmology: Pediatric ophthalmology and strabismus, San Francisco, 2012. Gerstenblith AT, Rabinowitz MP: The Wills eye manual, ed 6, Philadelphia, 2012, Lippincott, Williams & Wilkins. Nelson LB, Catalano RA: Atlas of ocular motility, Philadelphia, 1989, W.B. Saunders.

1.How are forced ductions performed?

Before beginning surgery, place an eyelid speculum in both eyes. Using oneor two-toothed forceps, grasp the conjunctiva at the limbus. Move the eye horizontally and vertically. The resistance encountered in moving the eye is compared with what normally would be expected, as well as with the resistance encountered in performing the same forced duction on the other eye.

2.Why perform forced ductions?

Forced ductions are performed to detect “tight muscles” or restrictions in eye movement. If the forced ductions indicate that a muscle is restricted, the affected muscle should be recessed. For example, if a patient has a vertical deviation, the superior rectus on the hypertropic side or the inferior rectus on the fellow eye may be recessed. If forced ductions show resistance to elevating the fellow eye, the preferred surgery is recession of the inferior rectus.

3.When correcting a horizontal or vertical strabismus, how do you decide how many muscles to recess or resect?

The angle of the deviation determines the number of muscles to recess or resect. Whereas a smallangle strabismus (<20 D) may be corrected by operating on one muscle only, a large deviation may require surgery on three or four rectus muscles. Most major texts contain tables that provide a guide as to how much surgery should be performed for the angle (measured in prism diopters) of strabismus. The tables indicate how many muscles should be operated on and the amount of recession or resection.

4.When doing a recess–resect procedure, should you first perform the recession or the resection?

The recession is performed first. In a resection the muscle is shortened and then brought forward to the insertion. This procedure creates tension on the resected muscle, making it difficult to bring the resected muscle to the insertion site. Initial recession of the antagonist muscle decreases the tension pulling the globe away from the resected muscle and makes it easier to bring the resected muscle to the insertion site and to tie the sutures tightly.

5.When performing surgery on an oblique muscle and rectus muscle of the same eye, on which muscle do you operate first?

The oblique muscles are more difficult to identify and isolate on the muscle hook than the recti. Strabismus surgery creates swelling of the Tenon’s capsule and bleeding, which can obscure the view and make identification of the oblique muscles difficult. Therefore, it is preferable to operate on the oblique muscles first when the Tenon’s capsule and the tissues surrounding the oblique muscles are the least swollen and distorted. The recti are more easily hooked and identified. There should be no difficulty

in isolating the correct rectus muscle, even in the presence of significant bleeding and swelling of the Tenon’s capsule following oblique muscle surgery.

6.What type of needle is used to suture the muscle to the sclera?

A spatulated needle has cutting surfaces only on the side and is flat on the bottom. This decreases the risk of perforating the globe. The sclera is thinnest just posterior to the insertion of the rectus muscles (0.3 mm).

Chapter 3: Parasurgical procedures and preparation”; © 2003-2014 Project Orbis International Inc. Link: http://telemedicine.orbis.org/bins/volume_page.asp?cid=1-2161-2253-2258

7.What is an adjustable suture?

Various techniques of placing and tying scleral sutures allow the muscle to be moved forward or backward during the immediate postoperative period. If a patient has an immediate overcorrection or undercorrection, the muscle can be moved to improve the alignment. This suture adjustment is performed within 24 hours of the initial surgery, often in the office.

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244  OPHTHALMOLOGY SECRETS IN COLOR

8.When should an adjustable suture be used?

The use of an adjustable suture is at the discretion of the surgeon. Some surgeons do not perform adjustable suture surgery, citing the fact that the correction seen immediately after strabismus surgery is variable and may not be indicative of the long-term result. Others use adjustable sutures in cases in which the results of strabismus surgery are difficult to predict, such as reoperations and restrictive or paralytic strabismus. Adjustable sutures are often used in patients with thyroid disease.

9.What is a transposition procedure?

A transposition procedure places the partial or entire tendon of the adjacent rectus muscles to the insertion of the palsied or underacting muscle. For instance, in double-elevator palsy the tendon of the lateral and medial recti may be sutured to the nasal and temporal borders of the superior rectus insertion.

10.When is a transposition procedure performed?

A transposition procedure is the procedure of choice when the function of one or more rectus muscles is severely limited, as with third-nerve, sixth-nerve, or double-elevator palsy.

11.How are A and V patterns of strabismus treated?

In cases of oblique muscle overaction, the appropriate oblique muscle should be weakened. Weakening of the inferior oblique muscles corrects a V pattern, whereas weakening of the superior oblique muscles corrects an A pattern (Fig. 27-1). In patients with no oblique muscle dysfunction, the horizontal recti are supraplaced or infraplaced. The medial recti are displaced toward the point of the A or V pattern, whereas the lateral recti are moved in the opposite direction. A useful acronym is

MALE, which stands for medial recti to the apex, lateral recti to the empty space. For example, to treat a V-pattern esotropia without oblique muscle overaction, the medial recti are recessed and infraplaced (moved inferiorly) by half of the tendon width.

12.What surgery can be done for Brown’s syndrome?

In Brown’s syndrome, a congenitally short or tight superior oblique tendon creates a mechanical restriction of elevation when the eye is in adduction, as confirmed at surgery with forced duction testing. Brown’s syndrome is treated surgically by superior oblique tenotomy, recession, or a tendon expander.

13.What are the indications for surgery in Brown’s syndrome?

Hypotropia in primary gaze or abnormal head position (face-turn or chin-up position) are indications for surgery. A significant deviation in primary gaze or abnormal head posture is the indication for strabismus surgery in most incomitant strabismus (Brown’s, Duane, superior oblique palsy, inferior oblique palsy, and monocular elevation deficit.)

14.In strabismus surgery in patients with Duane’s syndrome, is it better to recess or resect?

Resection would increase the globe retraction; therefore, resections are avoided. Recessions or, less commonly, transposition procedures are performed.

15.When performing vertical rectus transposition to treat a sixth-nerve palsy do you transpose both vertical recti or just one of the vertical recti?

One or both vertical recti can be transposed. Historically the superior and inferior recti are transposed temporally to treat a sixth-nerve palsy. More recently superior rectus transposition with recession of

Figure 27-1.  Displacement of horizontal arch in the treatment of A- and V-pattern strabismus.

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the medial rectus has been shown to be effective in treatment of sixth-nerve palsy. Transposing only the superior rectus reduces the risk of anterior segment ischemia.1

KEY POINTS: MOST COMMON COMPLICATIONS OF STRABISMUS SURGERY

1.Overcorrection or undercorrection

2.Anterior segment ischemia

3.Infection

4.Adherence syndrome

5.Diplopia

6.Scleral perforation

7. Slipped or lost muscle

8. Operating on the wrong muscle

16.What are the signs of infection after strabismus surgery?

Signs of infection are cellulitis, subconjunctival abscess, or endophthalmitis. Cellulitis is most common, with an estimated incidence between 1 case in 1000 and 1 case in 1900 surgeries. It typically begins 1 to 4 days after surgery. The most common symptoms are marked swelling and pain. Suspected cellulitis requires prompt treatment with systemic antibiotics as well as careful examination to make certain that the patient does not develop endophthalmitis.2

17.What are the signs and symptoms of endophthalmitis after pediatric strabismus surgery?

The signs of endophthalmitis appear 1 to 4 days after surgery and include lethargy, asymmetric eye redness, eyelid swelling, and fever. Patients who develop endophthalmitis experience an increase in eyelid swelling and redness during the postoperative period rather than a decrease, as expected during a normal postoperative course. On examination, the patient has a decreased red reflex and signs of vitreal inflammation. If endophthalmitis is suspected, prompt evaluation and treatment are required.3

18.What should you do if you suspect that you perforated the globe when passing the scleral suture?

If a scleral perforation is suspected, indirect ophthalmoscopy should be performed in the operating room at completion of the strabismus surgery. If a retinal perforation is seen on ophthalmoscopy, retinal consultation or repeat examinations with the indirect ophthalmoscope are indicated. Treatment is controversial. Whereas some surgeons advocate treatment with cryotherapy or indirect laser, others simply observe the patient. The incidence of retinal detachment after scleral perforation is believed to be low. At the same time, cryotherapy may increase the incidence of retinal detachment by stimulating vitreous changes. In patients predisposed to retinal detachment (for example, high myopes), however, serious consideration should be given to treatment of a retinal perforation at the time of strabismus surgery. Some strabismus surgeons believe that scleral perforation increases the risk of endophthalmitis and therefore recommend a sub-Tenon’s injection of prophylactic antibiotics if the globe is perforated.4,5

19.What is a slipped muscle?

The muscle is contained within a capsule. While operating on a rectus muscle it is possible to mistakenly engage only the capsule on the suture. After the muscle is reattached to the eye, it may slip back within its capsule, which results in further weakening of the muscle and consecutive deviation.

For instance, if a slipped muscle occurred in recessing a medial rectus muscle for esotropia, exotropia and limited adduction will develop in the involved eye over time.

20.How is a slipped muscle prevented?

When placing the suture through the muscle, make locking bites on either end of the muscle. Locking bites are made by placing the suture through the muscle perpendicular to its insertion, engaging the tendon, rather than tangentially. Tangential placement may engage only the capsule.6

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