TABLE 1. Patient Awareness of the Presence of a Cyclodeviation Relative to the Degree of Torsion as Measured by Double Maddox Rods

Our preferred method of testing for subjective torsion is the Lancaster red-green test (Fig. 1). This test allows the clinician to evaluate torsion in nine positions of gaze and clearly indicates where torsion is greatest and where vertical deviation is most significant. The test is performed in a darkened room so that no spatial clues in the environment can help in orienting the streaks of red and green light. By convention, a red filter is placed over the right eye and a green filter over the left. The examiner takes the light corresponding to the desired “fixing eye” and shines it on the wall successively in the nine diagnostic positions of gaze. In each position, the patient is asked whether the streak of light is straight or tilted. (We customarily do the test with vertical streaks, in that it is easier for the patient to describe tilt in a vertical streak than a horizontal streak.) If the streak is tilted, the examiner adjusts the light until the patient sees the streak exactly vertically. The patient then superimposes the second streak on the first streak. The examiner records the position and orientation of the streaks to analyze the torsional and vertical components of the deviation in the different fields of gaze (Fig. 2). The absolute horizontal deviation is difficult to judge with this test because of the poor control of accommodation provided by the streaks of colored light. The relative horizontal deviation, however, is reasonably reliable, and is used for judging A or V patterns.

Objective torsion is best assessed by indirect ophthalmoscopy or fundus photography.^2,5 For example, in a patient with V-pattern esotropia, the presence of fundus extorsion justifies inferior oblique weakening surgery in addition to horizontal surgery (Fig. 3).

In some situations, alternative approaches to surgical correction can have very different effects on the torsional deviation, and these effects should be considered when weighing the value of the alternative approaches. For example, if a patient presents with V-pattern strabismus but no fundus extorsion, the surgeon might choose to avoid oblique surgery and instead perform vertical transposition of the horizontal rectus muscles. However, if fundus extorsion is noted, transposing the medial rectus muscles downward or the lateral rectus muscles upward theoretically makes the extorsion worse, although Metz documented only small, nonsignificant changes in subjective torsion in similar cases.⁶

When recessing or resecting vertical rectus muscles, the surgeon should consider the resulting torsional effect. If a patient with superior oblique paresis undergoes recession of the ipsilateral superior rectus muscle, extorsion worsens. Simultaneous temporal transposition of this muscle may help lessen the extorsional effect.

Fundus intorsion is characteristic of most cases of Brown's syndrome. Brown's syndrome responds to superior oblique weakening, which simultaneously decreases the intorsion. In some cases of Brown's syndrome, however, there is no abnormal fundus torsion in primary position, but intorsion appears only in attempted upgaze in abduction. This suggests that the tendon of the relaxed superior oblique muscle will not pull forward through the trochlea. If only a superior oblique tenotomy is performed in this case, extorsion in primary position will result. In theory, therefore, inferior oblique weakening should be added when there is no fundus intorsion preoperatively.

In thyroid ophthalmopathy with a tight inferior rectus muscle, the eye is extorted. Recession of the inferior rectus muscle corrects the extorsion as well as the hypotropia. However, performing substantial bilateral inferior rectus muscle recessions may actually lead to symptomatic intorsion. This becomes symptomatic especially in downgaze because the superior oblique muscles become the primary depressors of the eyes, producing significant intorsion when unopposed by the extorting effect of the inferior rectus muscles. Accordingly, if no extorsion is present preoperatively, prudence dictates temporal transposition at the time of recession of the inferior rectus muscles to avoid the intorsional effect.

A head tilt associated with congenital nystagmus may respond to cyclovertical surgery. One approach, described by Conrad and de Decker in 1978,⁷ involves advancing or recessing the insertions of the oblique muscles. It makes good sense to operate on the oblique muscles to affect the torsional position of the eye, because torsion is the primary action of these muscles. Precise oblique muscle surgery may be technically difficult, however. Horizontal transposition of the vertical rectus muscles offers an alternative technique, and von Noorden and colleagues have described such a procedure to correct a head tilt in patients with nystagmus.⁷ Some other head tilts, with no apparent cause, may also respond to this approach.⁷

Surgeons with an incomplete understanding of torsional considerations, or inadequate equipment to evaluate cyclodeviations, should avoid surgical intervention until adequate assessment has been made.

HARADA-ITO PROCEDURE FOR EXTORSION

The Harada-Ito procedure on the superior oblique tendon is typically performed in cases with significant extorsion and little vertical deviation.¹⁴ With significant hyperdeviation and extorsion, a superior oblique tuck may be used but it is difficult to adjust. Pinchoff and coworkers described combining a tuck of one superior oblique and an adjustable Harada-Ito procedure of the fellow eye to correct asymmetric bilateral superior oblique paresis with a vertical deviation.¹⁵ Alternatively, an adjustable Harada-Ito procedure¹⁶ may be combined with adjustable vertical rectus muscle surgery.

In a typical Harada-Ito procedure, the superior oblique tendon is approached temporally to the superior rectus muscle by holding the eye down and in with a muscle hook under the superior rectus muscle. The anterior 25% to 40% of the superior oblique tendon is split from the rest of the tendon by blunt dissection with a small Stevens hook but is not disinserted. If a vertical effect is desired, a greater amount of tendon may be included. A double-armed suture is looped and tied around the anterior portion of tendon approximately 10 mm from its insertion (Fig. 4). Many surgeons use a nonabsorbable suture, but we have had good results with absorbable suture material. Apparently, the reaction incited by the resorbing suture material is sufficient to secure the superior oblique tendon to its new location.

Both needles are then passed through the sclera at a point superior to the lateral rectus muscle, 6 to 8 mm posterior to its insertion, so as to pull the anterior portion toward that point (Fig. 5). In the Fells modification of the Harada-Ito procedure, the anterior half of the superior oblique tendon is disinserted and moved temporally and anteriorly, attaching it to the sclera near the superior border of the lateral rectus muscle^17,18 (Fig. 6).

Our usual technique is an adjustable Harada-Ito procedure with a double-armed 6-0 Vicryl suture without disinserting the anterior portion of the superior oblique tendon (Fig. 7). An adjustable noose is tied around the sutures in a double loop followed by a square knot.¹⁹ A 5-0 Mersilene suture is also passed through partial-thickness sclera for retraction of conjunctiva during the postoperative adjustment.

Intraoperative adjustment of torsion is made by comparing anatomic torsion with the indirect ophthalmoscope before and after tightening the anterior tendon fibers. Generally, we place the fovea level with the center of the disc, finding that this amount of initial overcorrection yields good long-term results. This is our only means of adjustment in children who would be uncooperative for later adjustment at the bedside. In older children and adults, postoperative adjustment of torsion at the bedside is performed using the Lancaster red-green test in various positions of gaze. In the case of bilateral superior oblique paresis, approximately 3 to 5 degrees of immediate postoperative intorsion in primary position is desirable, more in upgaze, and less in downgaze. Each noose is adjusted, and the ends tied accordingly. This purposeful overcorrection usually disappears in the weeks following surgery, except for a small amount of consecutive intorsion in upgaze that may persist.

The Harada-Ito procedure is remarkably safe and effective, but there are several potential complications. First, although some intorsion in upgaze is usually required to achieve adequate torsional correction in downgaze, excessive intorsion in upgaze may be symptomatic. In addition, small vertical deviations may persist after bilateral Harada-Ito procedures. For this reason, we often put an adjustable suture on a vertical rectus muscle for postoperative modification. Finally, if the anterior portion of the superior oblique tendon is placed too far anteriorly, esotropia may be induced, especially in downgaze.

HORIZONTAL TRANSPOSITION OF THE VERTICAL RECTUS MUSCLES

The oblique muscles have the most torsional action in primary position, followed by the vertical rectus muscles, with essentially no torsional action from the horizontal rectus muscles. Therefore, in cases in which oblique surgery has failed and cannot be repeated, or an oblique muscle is congenitally absent, horizontal transposition of the vertical rectus muscles presents a viable alternative to oblique surgery for torsion^20,21 (Fig. 8). Transposing the superior rectus muscle nasally has an extorting effect, whereas transposing it temporally has an intorting effect (Table 2). Likewise, transposing the inferior rectus muscle nasally has an intorting effect, whereas transposing it temporally has an extorting effect. Therefore, transposition of the superior rectus muscle or the opposite transposition of the antagonist inferior rectus muscle 5 to 9 mm can either correct or induce abnormal torsion. For cyclodeviations that are predominantly in downgaze,transposition of the inferior rectus muscle may be preferable. Conversely, superior rectus transposition may be preferable if torsional deviations are more evident in upgaze. Temporal transposition, in either case, is likely to be more effective than nasal transposition, because temporal transposition gives the muscle more of a torsional direction of action.

TABLE 2. Obtaining Torsional Effect by Horizontal Transposition of Vertical Rectus Muscles

  To correct extorsion or create intorsion, transpose:
  Superior rectus temporally
  Inferior rectus nasally
  To correct intorsion or create extorsion, transpose:
  Superior rectus nasally
  Inferior rectus temporally

Not enough experience has been attained with this procedure to recommend specific amounts of transposition for desired degrees of torsion effect. It seems likely that its results will be less predictable than those of the Harada-Ito procedure, because the amount of transposition cannot be adjusted postoperatively.

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