Summary
Surgery on the superior oblique tendon includes both weakening and tightening procedures to address superior oblique abnormalities resulting in incomitant cyclovertical deviations, A-pattern strabismus, and torsional diplopia.
7 Superior Oblique Surgery
7.1 Goals
Improve ocular torticollis due to incomitant cyclovertical strabismus.
Improve diplopia caused by superior oblique abnormalities, including trochlear nerve (4th cranial nerve) paresis and Brown syndrome.
Improve A-pattern strabismus associated with superior oblique overaction.
7.2 Advantages
Treatment with superior oblique surgery is often more effective than prism glasses due to the presence of torsional diplopia and incomitance from superior oblique dysfunction.
Patients undergoing strabismus surgery for a horizontal deviation with a large A-pattern may benefit from simultaneous superior oblique surgery.
7.3 Expectations
Long-term resolution of diplopia including torsional diplopia.
Ability to resolve residual diplopia with prisms.
Improvement of ocular torticollis.
Improvement of A-pattern strabismus.
7.4 Key Principles
The superior oblique muscle and tendon have an unusual course in comparison to the other extraocular muscles, with significant variability in morphology, including reported absence in some patients. 1
The anterior fibers of the muscle primarily intort the eye, while the posterior fibers primarily depress the eye. Procedures such as the Harada-Ito procedure take advantage of the compartmentalized functions of the tendon to target the torsional function of the anterior fibers.
The superior oblique muscle also has a tertiary function of abduction, so that patients with bilateral superior oblique palsies present with esotropia in downgaze, resulting in a V-pattern esotropia.
7.5 Indications
Superior oblique weakening procedures:
Superior oblique tenotomy:
Superior oblique overaction causing A-pattern strabismus, hypotropia in primary gaze, or ocular torticollis (head tilt).
Not recommended for Brown syndrome due to risk of iatrogenic superior oblique paresis. 2
Superior oblique spacer:
Brown syndrome causing hypotropia in primary gaze, significant ocular torticollis (chin up), and diplopia.
Superior oblique overaction causing A-pattern strabismus, hypotropia in primary gaze, or ocular torticollis (head tilt), especially if normal stereoacuity is present.
Superior oblique tightening procedures:
Superior oblique tuck:
Superior oblique weakness due to unilateral trochlear nerve (4th cranial nerve) paresis resulting in ocular torticollis (head tilt or head turn), hypertropia, and diplopia.
May be considered bilaterally for bilateral trochlear nerve paresis if a very large esotropia is present in downgaze.
Harada-Ito procedure:
Bilateral superior oblique weakness due to bilateral trochlear nerve paresis with primarily torsional diplopia, alternating hypertropia in lateral gazes, and ocular torticollis (chin down).
If the bilateral trochlear nerve paresis is significantly asymmetric, resulting in both torsional and vertical diplopia, Harada-Ito procedure may be performed on the less affected eye, and a superior oblique tuck performed on the more severely affected eye.
7.6 Contraindications
Superior oblique tenotomy is not recommended in patients with normal stereoacuity, such as those with Brown syndrome and intermittent A-pattern exotropia, due to a greater risk of developing iatrogenic superior oblique paresis, resulting in torsional diplopia and ocular torticollis.
7.7 Preoperative Preparation
Evaluation of fundus torsion may be performed by assessing the position of the foveal reflex with respect to the optic nerve during indirect ophthalmoscopy of each eye (Fig. 6.1 in Chapter 6) while the patient fixates on a target, such as the tip of a pen, held between the condensing lens and the examiner in cooperative patients, or without fixation in younger patients.
For cooperative older children and teenagers, measurements of torsion with double Maddox rod testing or Lancaster red-green testing are done during the preoperative evaluation of patients with superior oblique abnormalities and diplopia.
7.8 Operative Technique
7.8.1 Exaggerated Traction Testing
Evaluation of the tightness of the oblique muscles should be performed bilaterally for comparison, including in cases of unilateral oblique muscle surgery.
After placement of an eyelid speculum, the globe is grasped with toothed forceps at the nasal limbus.
To evaluate the superior oblique tendon, the globe is retropulsed and adducted first. Then the globe is elevated and extorted, rocking the surface of the globe back and forth over the superior oblique tendon. The tightness of the superior oblique is compared to the tightness of the ipsilateral inferior oblique muscle, as well as the tightness of the contralateral superior oblique tendon and inferior oblique muscle.
To evaluate the inferior oblique muscle, the globe is retropulsed and adducted first. Then the globe is depressed and intorted, rocking the surface of the globe back and forth over the inferior oblique, which is felt as a “bump,” to determine the presence of laxity or restriction (Fig. 6.2 in Chapter 6). The tightness of the inferior oblique is compared to the tightness of the ipsilateral superior oblique tendon, as well as the tightness of the contralateral inferior oblique muscle and superior oblique tendon.
A superonasal or superotemporal fornix incision, as described in Chapter 3.8.1 Fornix Incision, may be used for superior oblique surgery, depending on the procedure performed and the surgeon’s preference.
7.8.2 Superior Oblique Tenotomy
A fornix incision is made in the superotemporal quadrant using blunt Westcott scissors, approximately 8 mm posterior to the limbus.
The superior rectus muscle is isolated first with a Stevens hook, and then with a Jameson hook, which is swept toward the limbus to ensure that the entire width of the muscle has been isolated.
A Stevens hook is used to reflect the conjunctiva over the bulb of the Jameson hook.
Blunt Westcott scissors are used to make a small incision in the intermuscular septum at the bulb of the Jameson hook, and a Stevens hook is inserted in the opening to perform a pole test to confirm that the entire width of the superior rectus muscle has been hooked.
A small Desmarres retractor is then placed in the conjunctival incision and positioned to expose the nasal aspect of the superior rectus muscle.
The Jameson hook is used to depress the eye and also displace the superior rectus temporally, and the Desmarres retractor is positioned for exposure of the nasal aspect of the superior oblique tendon just adjacent to and under the superior rectus muscle. The eyelid speculum may be removed at this time.
A Stevens hook, with its tip pointed nasally, is swept posteriorly along the nasal border of the superior rectus muscle to the posterior margin of the superior oblique tendon which is isolated onto the Stevens hook.
The Tenon’s capsule surrounding the tendon is carefully dissected with 0.3-mm toothed forceps and Westcott scissors. A second Stevens hook is passed under the superior oblique tendon in the opposite direction of the first Stevens hook.
Blunt Westcott scissors are then used to incise the tendon between the two Stevens hooks for a complete tenotomy.
All of the instruments are removed, and exaggerated traction testing is repeated to confirm that the superior oblique is free following complete tenotomy. Any residual tension suggests an incomplete tenotomy, which should prompt the surgeon to repeat the above procedure and explore for additional fibers of the superior oblique tendon that may have been overlooked.
The conjunctival incision is reapproximated, usually not requiring sutured closure.
7.8.3 Superior Oblique Tenotomy with Suture Spacer
Indirect ophthalmoscopy after pupillary dilation may be performed to evaluate fundus torsion for comparison during intraoperative adjustment.
A fornix incision is made in the superonasal quadrant using blunt Westcott scissors.
The superior rectus muscle is isolated with a Stevens hook, followed by a Jameson hook.
A Stevens hook is used to drape the conjunctiva over the bulb of the Jameson hook.
Blunt Westcott scissors are used to make an incision in the intermuscular septum just under the bulb of the Jameson hook, and a Stevens hook is inserted in the opening to perform a pole test to confirm that the entire width of the superior rectus muscle has been hooked.
A small Desmarres retractor is then placed in the conjunctival incision to expose the nasal aspect of the superior rectus muscle.
The Jameson hook is used to depress the eye and also displace the superior rectus temporally, and the Desmarres retractor is positioned for exposure of the nasal aspect of the superior oblique tendon just adjacent to and under the superior rectus muscle. The eyelid speculum may be removed at this time.
A Stevens hook, with its tip pointed nasally, is swept posteriorly along the nasal border of the superior rectus muscle to the posterior margin of the superior oblique tendon which is isolated onto the hook.
The Tenon’s capsule surrounding the tendon is carefully dissected with 0.3-mm toothed forceps and Westcott scissors. A Jameson hook is passed under the superior oblique tendon in the opposite direction of the Stevens hook. The Jameson hook on the superior rectus muscle is then used to replace the Stevens hook on the superior oblique tendon.
The superior oblique tendon is held taut by the two Jameson hooks.
A 6–0 double-armed nonabsorbable polyester suture is secured on the temporal aspect of the superior oblique tendon just nasal to the superior rectus muscle with a central full-thickness 2–1 throw square knot. One end of the suture is wrapped from the surface of the tendon, around and under the tendon, emerging to the surface again via a full-thickness pass at one edge of the tendon. The other end of the suture is wrapped in the opposite direction, around and under the tendon, emerging to the surface again with a full-thickness pass at the opposite edge of the tendon.
Both needles are then passed through the nasal aspect of the tendon from the underside of the tendon, approximately 4 to 7 mm from the temporal knot. The ends of the suture at the nasal aspect of the tendon are tied in an overhand knot, leaving ample length of suture between the tendon and the knot, and the needles are trimmed (Fig. 7.1).
Using two needle holders, an adjustable sliding noose using a segment of polyglactin suture without a needle is placed around the nasal ends of the suture spacer, which is held taut by the assistant with a needle holder, with two full turns and a 1–1 throw square knot. The ends of the adjustable sliding noose are tied together with an overhand knot, and the sliding noose is then adjusted for the suture spacer to be completely lax between the nasal and temporal tendon. A Stevens hook can be used to pull the slack of the suture between the temporal and nasal aspects of the tendon.
A remnant of single-armed 6–0 polyester suture is placed on the tendon just temporal to the nasal passes of the suture spacer. This suture is used as a traction suture to access the adjustable sutures and tendon during adjustment. This suture is secured on the tendon with a central full-thickness knot, pulling the suture more than halfway through the tendon before tying the knot. The long end of the suture is wrapped around the tendon and tied again, then wrapped in the opposite direction and tied a third time. The tails are trimmed to be asymmetric with one short tail and one long tail, for the traction suture to be easily differentiated from the suture spacer.
Once the suture spacer is in place and on maximum slack, the tendon is transected between the temporal knot of the suture spacer and the traction suture nasally. Extra care is taken to avoid cutting the suture spacer.
Exaggerated traction testing is repeated to confirm that the entire tendon has been transected. Then the adjustable sliding noose on the suture spacer is adjusted to leave a 4 to 8 mm gap between the cut ends of the tendon, depending on the preoperative examination and initial exaggerated traction testing.
The Jameson hooks and small Desmarres retractor are removed, and exaggerated traction testing is repeated in both eyes for comparison. If adjustment is needed, the Desmarres retractor and Jameson hooks are replaced by means of the traction suture, and the adjustable sliding noose is adjusted on the suture spacer. If the suture spacer is adjusted for greater weakening, a Stevens hook is used to pull the slack between the cut ends of the tendon.
Once the suture is adjusted, exaggerated traction testing is performed again, and Step 17 is repeated until traction testing in the operative eye is similar to that in the fellow eye, aiming for a small undercorrection. Fundus torsion may also be evaluated by indirect ophthalmoscopy to help finalize the position of the suture spacer.
Once the spacing between the cut ends of the tendon is finalized, the suture spacer is trimmed near the overhand knot and tied in a 3–1-1 throw square knot over the polyglactin adjustable noose.
The ends of the suture spacer, the adjustable sliding noose, which is absorbable, and the traction suture are all trimmed.
The hooks and Desmarres retractor are removed, and the conjunctival incision is reapproximated, usually not requiring sutured closure.
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