So what instrumentation is best for vitreoretinal surgery? A fairly straightforward question on the face of it, but it is,
in fact a surprisingly difficult question to answer. I intend to put forward the case for 23-gauge surgery, my preference,
and, in order to do this, I first need to explain why I generally prefer transconjunctival vitrectomy to traditional 20-gauge
vitrectomy. Finally, I will explain why I use 23-gauge rather than 25-gauge and why I do not perform 20-gauge transconjunctival
In answer to the first question: Why do I prefer the transconjunctival technique? Briefly, it involves no conjunctival or
scleral surgery, so it has no associated Vicryl-related inflammatory reactions and, in most cases, leaves the eye free of
irritation. Furthermore, it does not induce astigmatism, the operation time is usually shorter, the surgery cost is lower
and there is an almost complete lack of postoperative complaints over a shorter rehabilitation time. For me, however, transconjunctival
vitrectomy has other advantages that are at least as, if not more, important. For instance, it leaves much better conditions
for additional interventions, whereas after three multiple 20-gauge surgeries, the sclera would be largely destroyed.
Valved cannula makes an impact
There are two additional advantages to transconjunctival vitrectomy which are associated with the cannula itself, no matter
what its size. Firstly, the cannula protects the sclerotomy; even if the instruments were to be inserted and withdrawn a hundred
times during a two-hour procedure, the sclera around the sclerotomy would not be affected. It would not be torn, or shredded,
nor would it be enlarged as it would be during a traditional vitrectomy.
Secondly, the cannula decreases the vitreous incarceration. Although this has not yet been proven, I am convinced that it
is true for two reasons. Its lumen is smaller and the smaller the lumen the less vitreous can pass through it. Secondly, its
length is greater, again allowing less vitreous to escape than would during an open sclerotomy. The cannula, therefore, helps
to reduce the risk of postoperative traction retinal detachment. This is particularly applicable if you use a valved cannula
rather than a conventional cannula.
Valved cannulas alone are reason enough why I will never return to traditional vitrectomy. The valve system prevents the loss
of intraocular fluid when the surgeon switches instruments and the resistance from the valve should also be as low as possible
to ensure that the cannula is not inadvertently removed. They allow me to operate as I have always wanted to operate, namely
within a closed system, allowing for much quicker and safer surgery.
Minor disadvantages are easily overcome
Although transconjunctival vitrectomy does have tremendous advantages, I also accept its drawbacks, in particular the poorer
effectiveness of the instruments, the greater flexibility, and the lack of angled instruments. In order to combat these problems,
I use 23-gauge instruments, which are more stable and allow me to work more quickly than I could with 25-gauge instruments.
Some may argue that with 25-gauge instruments the sclerotomy can be made perpendicularly, whereas with 23-gauge a tunneled
incision must be made. However, this can be achieved so quickly and simply that it does not, in my opinion, represent a real
disadvantage. Quite the contrary, the tunneled sclerotomy is beneficial because it results in better closure than can be achieved
with a perpendicular 25-gauge sclerotomy.
At the cutting edge
Of all the instruments the cutter is most important. Everyone will agree that the smaller the opening, the more likely that
there will be closure by vitreous or epiretinal membranes and that shaving or removal of the membrane is quicker and far more
controlled. Theoretically this should be true of 25-gauge instruments. However, to perform shaving on the periphery, you need
stable instruments, an advantage of 23-gauge instruments. To combine both advantages, Dutch firm DORC has introduced a new
23-gauge cutter with a very small slit-like port. The port is located forward at the tip of the cutter, which is angled to
about 30° to allow manipulation very close to the retina (Figure 1).