•Forceps to grab and lift membranes.

•Scissors to lift membranes and/or cut42 membranes.

Viscodelamination and the probe are not reasonable options in dealing with PVR membranes. Bimanual surgery, however, is very helpful (see Sect. 24.2).

32.3.1.4 Surgical Steps

•Remove the lens if the eye is phakic.43

•Check if PVD has occurred (see below); if not, create one and carry it as anteriorly as possible.

Q&A

Q Is it acceptable if the creation of PVD causes retinal tears?

A It is preferable not to cause iatrogenic breaks. However, in diseases where the primary cause is traction, this may be a price worthwhile to pay if the vitreous can thus be separated from the retina. If a PVD cannot be created, retinectomy may be the next best option. The worst is to leave traction behind when breaks are also present.

•Find and remove all membranes.44

–This is much easier in the posterior pole than in the periphery.

–The membrane and the retina may adhere to each other as two sheets glued together, showing the crucial role the nondetached cortical vitreous plays in the process. If the membranes/posterior cortical vitreous complex is impossible to separate from the retina, the choice is between a retinectomy (see Sect. 33.1) and a SB (see Sect. 54.4).

•Check whether the retinal surface is now smooth; if not, the blood vessels remain corkscrew-like. Continue trying to identify and remove membranes until the retina is smooth.

–Remember that the cause may be a subretinal membrane.

•Using air or PFCL45, reattach the retina and check if it is under tension (air-test; see Sect. 31.1.2).

–If the retina does not readily reattach, remove the tamponade and continue searching for membranes or determine whether the retina is shortened and retinectomy is needed (see above).

•Repeat the F-A-X.

42Cutting (rather than removing) membranes is rarely done in anti-PVR surgery.

43Unless the patient is young, but even then sacrifice the lens if it prevents complete anterior vitrectomy.

44This is described in Sect. 32.2.

45See Chap. 35 for more details about tamponades.

•If the retina is reattached and appears completely normal:

–Perform laser treatment.

–Fill the vitreous cavity with silicone oil.

32.3.1.5 Closed Funnel/Retinal Incarceration

It is crucial to remove all preand subretinal membranes if the surgeon wants to reattach a retina in an eye where the disc is invisible.46

•Remove the subretinal membranes first.

–Membranes may be broken in 2; with the adhesion to the photoreceptors now only at a single site, the membrane will cease causing traction and can be left behind.47

•A crucial area is close to the disc, where a ring proliferation may be present; without breaking up and removing this ring, the retina will not reattach but in cross section resemble a bell curve.

–Injecting PFCL over the choroid helps keeping the retina in a relatively stable position, allowing the surgeon to manipulate over the photoreceptors without the mobile funnel blocking the view every time a membrane is lifted.

•When no subretinal membranes are visible anymore, diathermize the anterior part of the funnel or the incarceration.

–Not all surgeons use diathermy; however, because of the risk of bleeding and its consequences,48 it is highly recommended.

–The line of diathermy spots may be too anterior; the final location of the line will be determined only after both the vitreous and all proliferative membranes will have been removed from the inside the funnel. The goal is to leave a central retina that is devoid of the gel (complete PVD) and any membranes on either side.

Pearl

If it is not only a closed funnel, but the retina is also incarcerated into the eyewall, I leave a small area, maybe 2 clock hours, incarcerated until all manipulations inside the funnel are also complete – this makes the retina much less mobile, aiding the manipulations.

•PFCL will not be able to open the funnel and provide access to the inside; the only option is to use cohesive visco such as Healon (see Sect. 13.3.2).

–Inject the Healon as posteriorly in the funnel as possible and very slowly. Its strength is sufficient to tear the retina if the membranes are very adherent.

46The surgeon is looking at the back surface of the retina in a closed-funnel detachment. Obviously, what is called “subretinal membrane” here is initially over the retinal surface according to the surgeon’s view.

47The air-test will help determine whether this is the case (see above).

48Increased risk of postoperative PVR.

•Gradually remove the vitreous with the probe and all the membranes with forceps. The visco may have to be reinjected.

•When all the membranes are removed, cut the retina (see Chap. 33 for further details about retinotomy and retinectomy).

•Replace the visco with PFCL.

•If the retina is not completely flat or the retinal vessels remain distorted, look for more membranes on either surfaces of the retina.

•Perform laser treatment.

•Replace the PFCL with silicone oil.

32.3.1.6 ILM Removal

Removing the central ILM is the most important step in the prevention of new proliferation growing over the macula in case of PVR recurrence. As mentioned above (Sect. 32.1.4), always try to do the peeling in the largest possible area.

32.3.2 PDR49

Much of what has been described under Sect. 32.3.1 also applies for eyes with PDR. Only the significant differences are described below. Table 32.2 provides a direct comparison between the two conditions.

•Discuss with the patient what to do with the lens.50

–PPV-related cataract often presents later in diabetic eyes than it would in other conditions.

•Spontaneous PVD virtually never occurs in eyes with PDR, but the thin, membrane-like layer of cortical vitreous is invisible; only the behavior of the tissues being manipulated gives away its presence.

Q&A

Q How can the surgeon identify and remove this delicate membrane?

A The visible membranes are part of the anterior wall of this giant vitreoschisis cavity. Make an incision in the anterior wall just peripheral to the thick neovascular membrane. Use a barbed needle to pick up the thin epiretinal vitreous cortex, which may be multilayered and so adherent that the retina may get detached if blunt separation is attempted. Try carefully to extend the membrane detachment all the way to the periphery. Stop when the separation becomes impossible, hopefully before breaks appear. Any vitreous left behind must be further reduced via pneumovitrectomy (see Sect. 27.3.2), but always consider retinectomy as an option (see Sect. 33.1).

49With or without an RD component. More details are provided in Chap. 52.

50Retain it if the patient is young, but the lens should be sacrificed if it prevents complete anterior vitrectomy.

•The membranes in the anterior wall need not be completely removed.

–Complete removal is called delamination. This can be achieved using the tools and techniques described above but also by employing the probe at a high cut rate with a low aspiration/flow. Smaller-gauge probes and ones with a very distal port are especially excellent for this purpose. Viscoelastics may also be used, but they are less safe (see Sect. 13.3.1).

–Parts of the membrane may be circumcised: connections to adjacent areas are severed 360°. Such segmentation is especially useful when there is a risk of tearing the retina at this location with forceful removal/separation attempts. The membrane stump is diathermized and left behind.

–Bimanual surgery is especially beneficial in these eyes; typically, a forceps is held in the nondominant and the probe or scissors (spatula) in the dominant hand.

–The stump is also left on the disc, at least 1 mm in length. This allows the stump to be safely diathermized and prevents both intraand postoperative bleeding.

•Even if bevacizumab has been injected preoperatively (see Sect. 52.2), bleeding from newly formed or even normal-appearing vessels may occur. There are two related dilemmas for the surgeon: are you going to use diathermy? And if yes, when?

Q&A

Q Should all bleedings be diathermized?

A The rationale for using diathermy is that these bleedings are unlikely to spontaneously stop and especially to do so early, and the clot tends to adhere to the retina very strongly.

–Diathermy may be used on “continual” basis: every time there is a hemorrhage, the probe/forceps/scissors/spatula is exchanged for the diathermy probe, and the source of the bleeding is cauterized. The advantage of this technique is that all bleeding sources are easily identified and taken care of; the downside is that it requires numerous instrument exchanges.

–The alternative technique is to wait until all work is done and then cauterize the spots where bleeding still occurs. The advantage of this technique is that only a single instrument exchange is needed; the downside is that the blood rapidly coagulates in diabetes, and the clot may be difficult to remove. It may also adhere to the retina so strongly that it tears the retina upon being lifted.

Pearl

There may be vessels that do not bleed during surgery due to the elevated IOP intraoperatively; however, they will readily bleed postoperatively, causing disappointment both to the patient and surgeon. Try to provoke the bleeding during surgery by shutting off the infusion and aspirating some of the intravitreal fluid so that the IOP drops, and cauterize any hemorrhage that is observed. (In some machines the aspiration automatically restarts the infusion; in such cases use the flute needle to aspirate the fluid, not the probe.)