59.1General Considerations

Although scleromalacia is much less likely to occur following MIVS than after 20 g vitrectomy, there may be other causes1 of the VR surgeon having to face a sclera that is so thin that rupture threatens.

Pearl

Thinning of the sclera is the strongest argument against using scleral pockets to fixate a buckling element (see Sect. 54.4.2.6).

If vitrectomy needs to be performed on an eye that has an area of scleral thinning, even if it is not in an area where cannulas would be placed, the VR surgeon must consider using a patch (see Sect. 21.2.4 and Fig. 21.3). He can choose from several materials,2 but the technique of applying it is similar.

59.2Surgical Technique

•If possible, use general anesthesia to eliminate the risk of causing direct injury with the needle used for the periocular injection and from the extra pressure on the eyeball as a result of the fluid injected into the orbit.

•Never use oculocompression.

•During the entire operation, avoid any external pressure on the globe.

•Open the conjunctiva at the limbus, in a sufficiently large area. Make two radial cuts so that the entire area of thinning, plus an adequately wide healthy scleral margin on each side, is exposed.

1Autoimmune diseases, eyes with high myopia, chronic glaucoma etc.

2Homologous sclera, periosteum, dura mater etc.

F. Kuhn, Vitreoretinal Surgery: Strategies and Tactics,

DOI 10.1007/978-3-319-19479-0_59

–Be extremely careful when dissecting the conjunctiva; always use blunt scissors.

•Apply light diathermy, preferably with a probe that has a blunt tip, to shrink the prolapsing uvea. This may have to be repeated multiple times as the bulging may recur.

–Too much shrinking may result in an irregular pupil as the uvea is drawn toward the diathermy site – do not overdo the diathermy!

•Measure the area to be patched; add ~2 mm on all sides, and cut the graft tissue according to size and shape.

Q&A

Q What do you do when the graft abuts the cornea?

A The graft must be fashioned so that it terminates at the limbus; 10-0 nylon sutures are to be used to fixate the graft here. All knots must be properly buried.

•The graft is laid over the thin sclera; no wound is prepared (Fig. 59.1).

•Use interrupted 7-0 or 8-0 vicryl sutures to secure the graft to the sclera.

–Enter the recipient sclera first, about 2 mm from the edge of the graft, and then exit through the graft, without the needle going through the thin part of the sclera. This technique allows suturing without the need to grasp the donor tissue with a forceps, reducing the trauma to the tissue. As the needle enters and then exits the graft, hold the graft in place by laying the jaws of the forceps onto the tissue, holding it down, and having the needle exit between the forceps jaws (see Table 63.3).

•Make sure the graft is not stretched by the sutures.

–The knots of the vicryl sutures do not have to be buried.

•Meticulously cover the graft with Tenon’s capsule and the conjunctiva.

–At the limbus where the graft abuts it, leave a 1 mm band of conjunctiva to extend over the cornea. This will slide off spontaneously with time.

•Control the postoperative inflammation and IOP very closely.

a

C

TS

b

C

G ~2 mm

Fig. 59.1 Schematic representation of suturing a scleral patch. (a) The area of thin sclera abuts the limbus. (b) The patch is fashioned so that it overlays the thin area by ~2 mm, except at the limbus. (Unlike in real life, the thin area is shown here for demonstration purposes even after the graft has been laid over the sclera.) (c) Cross-sectional view to demonstrate the introduction of the vicryl suture to hold the graft. The thick arrows show the direction of the suture. C cornea, TS thin sclera, G graft, N/S needle-suture, S sclera