Fibrosis and scarring may affect alignment directly due to muscle contracture and indirectly via connective tissue restriction and conjunctival shortening. Techniques to correct alignment in the face of severe scarring include scar tissue recession, scar debulking, conjunctival recession, amniotic membrane grafting, and conjunctival autografting. Antifibrotic agents have not gained wide acceptance due to limited effectiveness and potential toxicity, but new agents may assist in the future.
28 Managing Excessive Scar Tissue (Adhesive Syndrome)
Fibrotic muscles and perimuscular fibrosis form the opposite end of the collagen spectrum from the disorders discussed in Chapter 27 and require very different approaches to surgical correction of strabismus. Excessive scarring after trauma, inflammation, or previous strabismus surgery can cause strabismus by several mechanisms, depending upon which layers are primarily involved. Intrinsic muscle fibrosis causes muscle shortening and excess action of the muscle. Scarring between layers, as in adhesive syndrome, restricts sliding of the layers and reduces range of movement of the eye, sometimes both toward and away from the involved area of fibrosis. Fibrotic distortion of the pulleys can change the muscle’s action in complex ways. External fibrosis and shortening of the conjunctival layers pull the eye out of alignment and restrict movement away from the area of fibrosis. Restoration of alignment in the primary position together with restoration of full range of motion is of course the preferred goal, but when scarring is too severe, one may need to be satisfied with centration of the eye. When muscle surgery alone is not enough, it is always possible to center the eye by manipulating the scar tissue layers themselves.
28.2 Scar Tissue Recession (IL)
If deep layers of perimuscular and periocular tissue are severely scarred and pull the eye out of alignment as well as limit movement, simple scar removal will only temporarily correct the problem, because the scar tissue will always reform. Scarring after repeat surgery is often worse than the initial scar. If the scar tissue layers are deliberately sutured to sclera in a gaze-neutral position or a gaze-shifting position, alignment can sometimes be corrected by scar tissue surgery alone. For example, severe nasal scarring that pulls the eye into esodeviation can be used to push the eye into exodeviation if the scarred layers are sutured behind the equator. This technique, which this author has termed “scar tissue recession,” has proven to be a useful method to center the eye in extreme fibrosis conditions.
Begin with intraoperative assessment of forced ductions in all directions, including torsionally. Inspect the conjunctiva and fornices for fibrosis and tissue loss (Chapter 3). Place the incision immediately anterior to scarred conjunctiva, in order to cause the least disruption of normal tissue. Dissect along the plane of the sclera, between muscle insertions, until enough sclera has been exposed that the targeted muscle may be isolated on a Stevens tenotomy hook, followed by a Green hook. This allows safe dissection without unplanned disinsertion of the muscle. Clear the sclera of scar tissue until restriction of movement is completely relieved. Sometimes at this point it becomes clear that the perimuscular scar tissue was the only cause of deviation, as the eye becomes well centered as assessed by the spring-back test (Chapter 3, Chapter 20). 1 If this is the case, proceed with the scar tissue management techniques; but if deviation persists, perform muscle recession first. Once the eye is centered, suture the deeper scar tissue layers to sclera (or muscle surface) with 7–0 or 6–0 polyglactin suture to maintain the eye in the centered position. If the restriction and deviation are severe, suturing those deep layers behind the equator can actually pull the eye into the opposite direction and assist in the correction of alignment. This principle allows correction of almost any angle of deviation but does create gaze restriction in the ipsilateral direction.
Precise placement of the scar tissue layers prevents postoperative shifting, reducing the risk of the eye pulling back toward its initial deviated position. Once the deep connective tissue layers have been sutured to sclera with good centration on spring-back test, then proceed to conjunctival recession, possibly with amniotic membrane graft or conjunctival autograft (Video 28.1).
28.3 Debulking of Scar Tissue
If subconjunctival scar tissue creates substantial thickening, then debulking the scar from the conjunctiva prior to scar tissue recession and conjunctival recession is in order. The assistant lifts the conjunctival edge with locking 0.5-mm forceps, and the scar tissue is carefully dissected free and excised from the conjunctival undersurface. This maneuver reduces unsightly conjunctival thickening and redness as well as postoperative discomfort. If the conjunctiva is not tight after debulking, then conjunctival recession may become unnecessary, and normal incision closure may be performed (Video 28.2).
28.4 Conjunctival Recession
After the eye has been centered surgically with direct muscle correction and scar tissue recession/debulking, the conjunctiva is assessed. When the conjunctiva is tight and direct closure (for a fornix incision) or repositioning at its original attachment site (for limbal or postlimbal incisions) causes the eye to deviate again, the conjunctiva should be recessed or sutured into an open position (Fig. 28‑1, Fig. 28‑2). The conjunctival edge is directly sutured to sclera with 7–0 polyglactin suture at a position that allows best centration of the eye with the least restriction of movement. The sclera may be left bare and will usually epithelialize, but sometimes, aggressive scar tissue will migrate over sclera and cause recurrent restriction. In this situation, or if a very large defect is created by conjunctival recession, covering the sclera with a barrier of amniotic membrane or a conjunctival autograft to prevent ingress of scar tissue is helpful. Amniotic membrane may also inhibit inflammation and promote regenerative wound healing.