to each other). There are several disadvantages – and not a single advantage – with this arrangement:5

•It prevents the surgeon from performing peripheral vitrectomy in the phakic eye inferiorly (see Figs. 21.2e, f).6

–This is often the real reason why surgeons feel the need to place an SB on the eye with RD if the retinal break is inferior (see Sect. 54.5.2.2).

•It makes it more difficult7 to access and work in the periphery superiorly.

•Holding the hands closer together is less comfortable than keeping them further apart (as in the latter scenario with sclerotomies placed more inferiorly).

–During a long surgery, less comfort can easily translate into less precision.

Placing the working sclerotomies very close to, but not right over,8 the 3 and 9 o’clock locations alleviates all these problems, without introducing any drawback. If the surgeon switches hands, he can access any location the vitreous cavity and do so comfortably.

The traditional site of the infusion cannula is at 4 o’clock. I place mine more toward 5 o’clock9 to make sure that there is enough room between the valves of the two temporal cannulas.

21.2.3 In Case of a Reoperation

This is a relatively common problem.

Q&A

QIf an eye requires re-PPV, should the same site be used for the sclerotomies?

AIf the reoperation is performed early (within days/few weeks), the wound has not yet healed. If the original wound can easily be identified, it is preferable to reuse them. If the reoperation is performed at least several weeks after the previous surgery, any location is suitable.

In MIVS, it may be very difficult to identify the exact location of the previous sclerotomy without opening the conjunctiva – which would defeat one of the purposes

5The most common reason for the erroneous site selection is simply that the surgeon does not consciously plan it (see 2.1.1).

6Between 5 and 7 o’clock.

7Not impossible, though.

8This is very important to avoid damaging the long ciliary nerves and arteries.

9In the left eye; in the right eye this is obviously mirrored.

of the transconjunctival approach. One advantage of always using identical clock hours during the primary PPV is to have a good idea where the sclerotomies should be found.

21.2.4 In Case of Scleral Thinning

If the sclera, for whatever reason (see Table 21.1 and Chap. 59), is visibly thin in the planned sclerotomy area, the site needs to be changed. An individual decision must be made to identify the most suitable and least inconvenient location. Scleroplasty (see Fig. 21.3) may be necessary even if the planned sclerotomy sites are outside the area of scleral thinning: the pressure needed to penetrate the sclera, inadvertent mechanical trauma during surgery, or the elevated IOP may cause a rupture with disastrous consequences.

a

b

Fig. 21.3 Scleral thinning. (a) This patient had severe autoimmune disease and extreme scleral thinning with extensive choroidal prolapse. Before vitrectomy for a VH could be performed, scleroplasty was necessary. (b) Once the scleral graft has been secured, VR surgery became possible; the sclerotomies were placed outside the area of scleroplasty