Superior Oblique Procedures
HongVan Le, MD
SUPERIOR OBLIQUE MUSCLE
The superior oblique (SO) intorts, depresses, and abducts the eye (see Chapter 42). Patients with a SO palsy will typically demonstrate a hypertropia that increases in adduction of the affected eye, as well as extorsion. Subjects with a SO palsy may have normalappearing versions, and the Parks-Bielschowsky three-step test can be helpful to make the diagnosis. The three-step test has a 70% sensitivity1 and 50% specificity.2 Bilateral SO palsies often cause increased extorsion and a large V-pattern esotropia. In some instances, a strengthening procedure such as a SO tuck can help to address vertical and torsional alignment issues due to a SO palsy. The Harada-Ito procedure is used to address excyclotorsion (without much vertical misalignment) by advancing the anterior portion of the SO (forwards and laterally) so that the axis around which the SO rotates the globe is closer to the anterior-posterior axis. Other surgical options for SO palsy may include weakening the ipsilateral antagonist (the inferior oblique, see Chapter 46) or weakening the yoke muscle (the contralateral inferior rectus). In contrast, SO overaction can result in an A-pattern strabismus (see Chapter 51). In these cases, SO weakening procedures such as tenotomy, partial tenotomy with or without a spacer can be helpful. Brown syndrome (SO tendon sheath syndrome) may also require SO weakening procedures. Caution should be taken in performing SO procedures in fusing patients as torsional issues can arise.
SUPERIOR OBLIQUE EXPOSURE
Positioning:
The patient’s head should be angled with the chin up so that the forehead is level with the operating table, and the superior orbital rim is perpendicular to the operating table.
The surgeon should sit so that the dominant hand has good access to the superior fornix. Often sitting on the same side of the patient as the dominant hand works well. Alternatively, the surgeon may want to sit opposite the eye operated.
Nasal approach to SO tendon (Fig. 47.1):
Place a single 6-0 silk traction suture or locking Moody forceps at the 12 o’clock limbus and rotate the eye downward.
Make an opening through the conjunctiva and Tenon capsule just nasal to the border of the superior rectus (SR) and extend posteriorly for several millimeters using the Westcott scissors (Fig. 47.1A).
FIGURE 47.1. Nasal approach to superior oblique exposure.
Hook the SR muscle, taking care to not pass the hook too far posteriorly to avoid hooking the SO tendon (Fig. 47.1B).
Once the SR muscle is hooked, the incision can be enlarged along the border of the SR muscle (Fig. 47.1C). Insert a small Desmarres or Fison retractor into the conjunctival and Tenon capsule opening to allow for adequate exposure.
Use sharp and blunt dissection to identify the SO tendon. Be careful when dissecting tissues between the SR and sclera so that the SO is not inadvertently injured (Fig. 47.1D). The SO fibers can be identified as silvery, white and running from underneath the SR muscle and coursing nasally.
Place a small Stevens tenotomy hook underneath the SO tendon making sure to rotate the point of the tenotomy hook upward to secure the tendon on the hook (Fig. 47.1E).
Gently remove any intermuscular septum still adherent to the tendon by grasping the tissue with forceps on either side and forcing the blunt end of the tenotomy hook up through the tissue (Fig. 47.1F).
Pass a second Stevens tenotomy hook through the opening created on either side of the SO tendon and then gently spread the hooks.
To confirm that the tissue isolated is the SO tendon, place a finger on the trochlea and pull on the tendon gently with the muscle hook. The pulling on the tendon should be felt at the trochlea.
Temporal approach to SO tendon (Fig. 47.2) (Video 47.1):
Place a single 6-0 silk traction suture or locking Moody forceps at 12 o’clock limbus and rotate the eye downward. Make an opening through the conjunctiva and Tenon capsule along the lateral border of the SR. (Fig. 47.2A).
Isolate and hook the SR muscle near its insertion taking care to not pass the hook too far posteriorly, which may inadvertently engage SO fibers (Fig. 47.2B). Insert a Desmarres or Fison retractor into the conjunctiva and Tenon capsule opening to allow adequate exposure to the superior fornix and to the SO tendon insertion.
FIGURE 47.2. Temporal approach to superior oblique exposure.
While retracting the SR nasally, use an iris spatula (tiny malleable ribbon retractor) or a smooth forcep to gently dissect and elevate the fine, silvery fibers of the SO tendon from the sclera by gently moving the instrument side to side and pushing the tip posteriorly (Fig. 47.2C). If the SO tendon is not obvious, start more anteriorly, close to the SR insertion for this maneuver. If the SO still is not apparent, pull the superior rectus more nasally to look for the insertion. Be aware that the anatomy may be abnormal in cases that require SO surgery.
Place a Stevens tenotomy hook underneath the SO tendon insertion until the posterior border is reached. When the tip is beyond the posterior edge of the tendon, rotate the hook end superiorly (Fig. 47.2D). Use forceps to gently remove the fibers of the intramuscular septum. Care should be taken during this step to avoid damaging the superior temporal vortex vein, which lies just posterior to the insertion of the SO tendon.
Once the SO tendon is isolated on a Stevens tenotomy hook, pass a larger Jameson muscle hook underneath the insertion to encompass the entire tendon (Fig. 47.2E).
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