Superior oblique tuck at the insertion
An effective and safe technique for strengthening the superior oblique is a tuck of the tendon at its insertion. This procedure maintains the normal action of the superior oblique muscle and reduces the incidence, severity, and persistence of postoperative Brown syndrome if appropriate precautions are taken. Tuck of the superior oblique tendon should be performed only if a loose, lax, or redundant tendon is confirmed, first at the superior oblique traction test and then by direct observation. Aloose tendon is seen in congenital superior oblique palsy, but usually not in acquired superior oblique palsy. After the tuck has been secured, passive ductions should be performed testing elevation in adduction. If the superior oblique traction test is too tight when comparing it to the fellow eye, the suture securing the tuck should be released and the size of the tuck reduced. The tuck should be secured only when passive elevation in adduction is equal or slightly tighter on the tucked side. The size of the tuck depends entirely on the laxity of the tendon. I once made a 22 mm tuck on a lax tendon without producing Brown syndrome in a congenital superior oblique palsy. On the other hand, I have produced severe Brown syndrome after a 6 mm tuck in a case of acquired superior oblique palsy, performed before I became aware of the pitfalls of iatrogenic Brown syndrome after tucking a normal (nonredundant) tendon.
The incision for exposure of the superior oblique tendon at its insertion is begun at the lateral border of the superior rectus insertion and extends temporally for 8 mm parallel with the limbus. The initial incision is carried through the conjunctiva, anterior Tenon's capsule, and intermuscular membrane. A muscle hook is inserted behind the insertion of the superior rectus muscle and a second hook retracts the posterior border of the incision at the lateral border of the superior rectus muscle. This maneuver exposes the insertional fibers of the superior oblique tendon. A muscle hook is inserted behind the insertion of the superior oblique tendon and the tendon is brought out from beneath the superior rectus (see Figure 14 in Chapter 9). If a tendon tucker is used, the hook is replaced with the hook portion of a Bishop or equivalent tendon tucker.
The knurled knob at the head of the tendon tucker is screwed down until the slack has been taken out of the superior oblique tendon. The total amount of tendon tucked is
twice the amount shown on the tucking instrument because the tendon is doubled on itself during the tucking procedure. It is impossible to give a number in millimeters for the correct amount of superior oblique tucking in a given case. However, it is safe to say that more errors are committed by doing too large than too small a tuck. In general, the more vertical deviation to be treated and the more lax the superior oblique tendon the greater the tuck required. When a sufficient amount of superior oblique tendon has been brought into the tucker to take out the slack in the tendon, Nonabsorbable suture (my choice is 5-0 Mersilene) is then used to anchor the tuck of the superior oblique tendon. A loop may be left in the knot securing the tendon at the base of the tuck to facilitate suture release and replacement if needed. Passive ductions are then performed. The tuck is reduced if passive elevation in adduction is limited. The tuck is made larger if the tendon remains lax on superior oblique traction testing.
Each border of the tendon is secured when the tuck is just right, the tucker is removed and the tuck remains intact. A third suture is placed at the apex of the tucked tendon, and this tip is attached to the sclera in line with the normal pull of the superior oblique tendon. The needle should be placed into very superficial scleral fibers because the sclera can be extremely thin in this area. The conjunctiva is closed with several interrupted sutures.
A tuck of the superior oblique tendon can also be carried out with a free hand technique. With this technique, the surgeon simply pulls the redundant tendon up with a hook and places the sutures through the superior oblique tendon at the level of sclera, producing the intended amount of tuck (Figure 21). This is my preferred technique.
A Incision for exposure of the superior oblique tendon at the insertion.
B Exposing the superior oblique insertion.
C The superior oblique insertion is engaged on a hook.
D The hook of the tucker engages the tendon.
E The tucker is adjusted pulling the loop of the tendon up until the intended amount of tuck is achieved and a suture secure the tuck at the borders of the tendon. The intended amount of insertion is determined after confirmation that the superior oblique traction test is equal or slightly tighter on the operated side.
F A second suture secures the tuck and the tip of the loop is sutured to sclera.
G conjunctiva is closed.
H A free hand tuck can be done after pulling up the lax tendon. A 5-0 merseline suture joins the arms of the loop near the base.
I When performing a tuck with either technique, a loop should be left in the initial knot so that it can be undone easily in the event that the tuck must be adjusted because it is too loose or too tight. When the tuck is the correct amount, the knot is tied and a second suture may be added.
Superior oblique resection and advancement
Other techniques for strengthening or shortening the superior oblique tendon are resection, advancement, or resection and advancement. For superior oblique resection, I prefer to attach the proximal tendon to the middle, posterior, or anterior insertion with placement depending on the amount of preoperative torsion. One reason for choosing tuck over resection for the superior oblique is that it can be difficult to place sutures in the thin superior oblique tendon.
The superior oblique tendon is exposed at the insertion (Figure 22). The tendon is engaged on a hook near its insertion and the superior rectus muscle is retracted medially. A 6-0 Vicryl or 5-0 merseline suture is woven through the tendon 6 to 10 mm or more from the insertion. The distance may be greater with a very loose tendon and less for a tendon that is not so loose. A hemostat is placed across the tendon toward the insertion a few millimeters from the suture and the tendon is cut between the hemostat and suture. The hemostat holds the distal superior oblique tendon, stabilizing the insertion. The double-arm Vicryl suture attached to the proximal tendon is brought through the insertion at the middle, posterior edge, or anterior edge. The middle is selected if the torsional and vertical defects are proportional, posterior if the vertical defect is greater, and, as occurs more commonly, anterior if extorsion is the main preoperative problem. The tendon can be advanced (attached farther temporally) or shifted anteriorly if more torsional effect is needed. Also, any of these procedures can be performed with an adjustable suture. Anteriorly placed sutures are more readily adjusted than posteriorly placed sutures.
As with any procedure to ‘strengthen’ the superior oblique, passive ductions should be tested and the tightness of the tuck adjusted to a point where the two sides are equal or the treated side just slightly tighter.
A The superior oblique tendon.
B After the loose tendon is elevated, a double arm suture is placed at the intended amount of resection.
C The tendon is cut distal to the suture and the suture is passed through the tendon insertion.
D The distal tendon is excised.
E The tendon is tied securely to the insertion, after adjustment, if needed, based on superior oblique traction testing.
F The excised tendon.
G The tendon can be shifted anteriorly if more effect on torsion is required. It may also be tied over a bolster if adjustment is planned.
H The tendon may also be advanced.