Conjunctival Incisions and Muscle Isolation
Tanya Glaser, MD
PREOPERATIVE CONSIDERATIONS
All strabismus surgery requires an incision through the conjunctiva and Tenon capsule to allow access to the extraocular muscles in the episcleral space. The two most common incisional approaches are the limbal approach and the fornix (cul-de-sac) approach. Key questions to consider when selecting an incision type include patient age and conjunctival integrity, history of prior surgery (strabismus, glaucoma, or retinal detachment), number of muscles needing to be accessed, and potential for discomfort or scarring. For instance, an inferotemporal fornix incision might be optimal for a young patient undergoing a lateral rectus muscle recession and inferior oblique myectomy because it provides easy access to both muscles. On the other hand, a limbal incision might be used in an older patient with conjunctival scarring who needs a medial rectus muscle advancement for overcorrection after a prior recession. Regardless of which type of incision is used, a drop of topical 2.5% phenylephrine prior to starting strabismus surgery helps to provide vasoconstriction and prevents bleeding. A 6-0 silk traction suture (in older patients with thinner, fragile conjunctiva) or Moody locking forceps (in younger patients with thicker conjunctiva and Tenon capsule) may be used prior to creating an incision to help stabilize the globe and improve exposure.1,2,3
A well-placed conjunctival incision is critical to successful strabismus surgery as it will determine exposure, ease of muscle manipulation, and closure. While there are pros and cons to each incision type (Table 43.1), two surgeons may use different incisions for the same surgical procedure.
SURGICAL PROCEDURE: LIMBAL INCISION AND MUSCLE ISOLATION (VIDEO 43.1)
In the limbal approach, the initial incision is made at the limbus with the base of the incision at the fornix. The incision is made where conjunctiva and Tenon capsule are fused, thus maintaining alignment of these structures and limiting adhesions between conjunctiva, Tenon capsule, and sclera.
Using a toothed forceps, elevate the conjunctiva and Tenon capsule about 2 mm from the limbus and to one side of the muscle insertion. Use Westcott scissors perpendicular to the limbus to make a single cut (large enough to insert the Westcott tips) through these tissues down to bare sclera.
Turn the Westcott scissors so they are flush with the globe, enter the incision and bluntly dissect to create a space between the sclera and overlying tissues, parallel to the limbus for ˜2-3 mm.
Release the tissue from the limbal edge by placing one blade into the dissected space, one blade above and against the limbus, and cutting in a single smooth motion along the limbus for ˜2 clock hours (to access a single rectus muscle, larger if accessing adjacent rectus muscles).
Reapproximate the edge of the conjunctival incision/flap. Extend the initial radial incision (currently 2-3 mm in length) to about 8 mm using the Westcott scissors. If accessing the medial rectus, stop the radial incision proximal to the plica semilunaris (semilunar fold).
Make a similar radial incision on the other side of the limbal opening. The two radial incisions should be at an obtuse angle to the limbus, creating a rhomboid shape (Fig. 43.1).
At each side of the base, lift the edge (placing Tenon capsule on stretch) and push the closed Westcott scissors into the oblique quadrant between adjacent rectus muscles. Bluntly dissect until an opening is made through Tenon capsule and bare sclera is seen. Be sure to point the scissors between muscles, not over the muscle.
Use muscle hooks and the two openings in Tenon capsule to isolate the rectus muscle insertion. This can often be done with direct visualization of the muscle edge.
One technique uses a small Stevens tenotomy hook to initially engage the muscle. Next, a Jameson muscle hook is inserted and passed just posterior to the Stevens tenotomy hook, isolating the entire rectus muscle insertion. If done correctly, the Jameson muscle hook should pass through the first opening in Tenon capsule, then under the muscle, and then out the second opening in Tenon capsule.
Elevate the conjunctival flap to allow further dissection of the Tenon capsule and intermuscular septum from the muscle body anteriorly. Avoid opening posterior Tenon capsule as this will result in orbital fat coming forward.
To close the limbal incision, identify the conjunctival edge of the flap and reapproximate its location at the limbus. At each corner, place an 8-0 Vicryl (or other absorbable suture) 1 mm posterior to the conjunctival edge of the flap and suture this to the limbal conjunctiva. It is important to avoid including Tenon capsule with this suture pass. In some cases, it may be difficult to distinguish Tenon capsule from the conjunctiva, and, in these instances, it can be helpful to hydrate the tissue to provide more contrast between the tissues. In addition, the conjunctival edge will occasionally fold under the flap and grasping the Tenon on the underside of the flap will help delineate the conjunctival corner. There is often redundant conjunctiva and Tenon capsule after a resection, advancement, or plication. Care should be taken to not mistake the plica for the edge of conjunctiva, and a very small amount of conjunctiva may need to be trimmed to prevent overhang of redundant tissue at the limbus.1,2,4,5
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