The superior oblique tendon is approached at its insertion in the superotemporal quadrant, or at its ropelike tendon superonasally, adjacent to the nasal border of the superior rectus muscle. Strengthening procedures are mainly done at the insertion, and include the full tendon advancement, tuck, resection, anterior plication, and Harada-Ito procedures. Insertional weakening procedures are the hang-back recession, direct recession, tenectomy, and anterior mini-tenotomies. Weakening procedures of the tendon in the superonasal quadrant are the tenotomy, “tenotomy with extender band” (also known as tenotomy with silicone spacer), and tenotomy with “chicken suture.”
26 Superior Oblique Surgical Techniques
26.1 Torsional and Exaggerated Forced Duction of the Superior Oblique
Before superior oblique (SO) surgery, with the patient under general anesthesia with skeletal muscle paralysis, torsional forced duction testing is performed 1 (Box 26.1, Chapter 9). The resistance to pure excyclotorsion and incyclotorsion is assessed by grasping the limbal conjunctiva at the 3 o’clock and 9 o’clock positions, slightly proptosing the eye, and estimating the degrees of rotation achieved before meeting resistance. Approximately 60 degrees of incyclotorsion and excyclotorsion is found before resistance is encountered in normal cases, and up to 90 degrees of excyclorotation in cases with SO laxity (Fig. 26‑1, Fig. 26‑2, Fig. 26‑3). Exaggerated forced duction of the obliques is also performed. 2 Torsional forced duction assesses the anterior fibers of the superior and inferior obliques, and exaggerated forced duction provides information about the posterior fibers. These maneuvers help to confirm SO laxity in congenital cases and rule out possible masquerade syndromes such as contralateral inferior rectus (IR) fibrosis. They are also repeated at the conclusion of surgery to confirm sufficient weakening or strengthening of the SO (depending upon the procedure).
Abnormal adhesions between the intraconal and extraconal spaces of the orbit severely inhibit the rotation of the globe during torsional forced duction testing and can cause a false negative test for SO palsy. Combined facial and head trauma can lead to combined cranial nerve and direct eye muscle trauma, causing the torsional forced duction test to be misleading in these patients. Pulley heterotopias also impact torsional forced duction testing and can simulate SO laxity or tightness. The exaggerated traction test 2 should not be impacted by pulley abnormalities and can help distinguish between SO and pulley abnormalities.
26.2 Isolating the Superior Oblique Insertion
A superotemporal fornix incision is made according to the method of Parks 3 (Chapter 23, Fig. 23.1, Fig. 23.2), the superior rectus (SR) muscle is isolated on a Green hook, and the eye is depressed. The Desmarres retractor is used to expose the superotemporal quadrant of the eye, and the lid speculum is removed. No dissection is required to isolate the SO tendon, which is found under the lateral border of the SR muscle, with its anterior insertion located about 7 to 8 mm behind the temporal pole of the SR insertion. The SO insertion is swept onto a small muscle (Stevens tenotomy) hook with the aid of toothed forceps. A second small muscle hook is swept around the posterior SO insertion to confirm that no tendon fibers have been missed (Fig. 26‑4). 1 , 4
26.3 Isolating the Superior Oblique Tendon
Although the ropelike tendon of the SO is found nasal to the SR muscle, it is approached through a superotemporal fornix incision, to avoid disturbing the surrounding capsule and intermuscular septum. In the case of tenotomy, these layers maintain the path of the tendon and prevent inadvertent displacement of the proximal cut end of tendon, which could adhere to the nasal border of the SR muscle insertion and cause upgaze restriction. 5 The SR is isolated on a Green hook, the eye is depressed, and the eyelid speculum is removed. Conjuctiva and Tenon’s capsule are retracted over the SR muscle insertion, and the Desmarres retractor is placed over the SR muscle to expose the nasal border. A small incision is made through the “check ligament,” which is fused on the posterior surface of the SR, at the nasal border of the SR. Two Stevens tenotomy hooks are inserted into this opening, which is stretched open to allow placement of the Desmarres retractor. This allows identification of the SO tendon nasal to the border of the SR. The capsule over the tendon is incised, and the tendon is delivered through this opening with a Stevens tenotomy hook.
26.4 Superior Oblique Strengthening Procedures
26.4.1 Full Tendon Advancement of the Superior Oblique (IL)
Begin with torsional and exaggerated forced duction testing (Section 26.2 Torsional and Exaggerated Forced Duction of the Superior Oblique), and isolate the SO tendon insertion (Section 26.3 Isolating the Superior Oblique Insertion, Video 26.1, Video 26.2).
A 6–0 polyglactin suture on a curved spatulated needle is placed through the insertion with anterior and posterior lock bites (Fig. 26‑5). The tendon is disinserted, advanced, and reattached with the double crossed-swords technique (Chapter 23) in the desired position. Advancement is measured, usually circumferentially, from the original insertion using calipers; anterior or posterior displacement may be added as desired, to decrease or increase the vertical effect, respectively.
Care is taken to maintain the natural curve and angled orientation of the SO insertion. Therefore, the anterior suture is passed sagittally, in an anteroposterior direction, and the posterior suture is placed horizontally from nasal to temporal in direction (Fig. 26‑6). A temporary slipknot tie may be used to secure the muscle position in order to confirm correct positioning of the insertion by repeating the pure excyclotorsion forced duction test. If resistance is met at the desired 60-degree point of excyclorotation, the knot may be permanently tied, or if not, the insertion may be repositioned forward or backward as necessary. A central lock bite is then used through the insertion to restore the natural curvature (Fig. 26‑7).
If the tendon is very lax, then it may be resected and advanced simultaneously. Place the suture several millimeters behind the insertion (Fig. 26‑8), excise the tendon distal to the suture, and advance the tendon (Fig. 26‑9) enough to produce the desired resistance on excyclorotation during the torsional forced duction test. Examination of the fundus may be performed to confirm full correction of torsion.
26.4.2 Superior Oblique Tuck
See Chapter 24.
26.4.3 Superior Oblique Resection (IL)
Resection of the SO tendon with resuturing to the original insertion was reported by Caldeira, 6 as a safe procedure, but more surgically stable than the tuck. The SO tendon is isolated at its insertion (Section 26.3 Isolating the Superior Oblique Insertion), and the SR muscle, which is held on the Green hook, is retracted nasally. The SO tendon is stretched by pulling it temporally, and the planned resection amount is measured with calipers. An absorbable suture is placed at that position with securing lock bites, the tendon anterior to the suture is excised, and the tendon is sutured to the original insertion. Having a two-sided wound increases the surgical stability as compared with the tuck, but the full tendon advancement of the SO has more flexibility, especially in cases of congenital malinsertion of the SO tendon, which would not be corrected by the SO tuck or resection.
26.4.4 Harada-Ito Procedure (IL, MS)
The original Harada-Ito procedure described anteriorization of a central split of the first 5 mm of the SO, without disinsertion of the tendon. They tied the muscle to the sclera 5 mm temporal to the insertion of the SO. 7
The Fells modification of the Harada-Ito procedure 4 , 8 disinserts the anterior third of the SO tendon, which is advanced with sutures to 8 mm posterior to the upper pole of the lateral rectus (LR) (Video 26.3). To do this, the SO tendon insertion is isolated as described in Section 26.3 Isolating the Superior Oblique Insertion. The tendon is split in half lengthwise with the Stevens tenotomy hook, for a distance of 10 mm from the insertion. A 6–0 polyglactin suture is placed through the anterior tendon insertion, which is disinserted with Westcott scissors. The LR muscle is then isolated on a Green hook, the eye is adducted, and the Desmarres retractor is used to expose the upper border of the LR muscle. The half-tendon is sutured to sclera 8 mm behind the insertion of the LR muscle within 4 mm of its superior border. Smaller advancements may be performed by measuring circumferentially from the original SO insertion, similar to the full tendon advancement (Section 26.5.1 Full Tendon Advancement of the Superior Oblique (IL))