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•It is best to start the membrane work in the center and gradually move toward the periphery.
•Unlike eyes with PVR, here the retina is not healthy; its tolerance (resistance) to traction during blunt membrane separation is much lower – in other words, the retina tears much more easily.
•If a retinal break is created, it becomes even more important to fully relieve all tractions.
•The macula is often spared by the thick membranes but is covered by thin ones52 and is edematous. ILM removal is therefore highly recommended. Often it is only after the ILM peeling when the surgeon realizes the vastly different appearance of the central retina, how much material he had removed, and how difficult it would have been for the macula to recover without ILM peeling.
•As mentioned above, if the peripheral vitreous cannot be separated from the retina, retinectomy may be needed (see Chapter 4.17).
•Panretinal laser is always necessary.
•The benefits of silicone oil implantation include bleeding prevention, maintaining retinal attachment, and allowing visualization of the retina even in the immediate postoperative period.
–Conversely, the retina may not tolerate the physical presence of the oil, especially if the retina is ischemic.
–The recurrence of the proliferation is often a mixture of PDR and PVR. This is one of the most difficult challenges to the VR surgeon because of the technical complicity in trying to remove thick, strong, adherent membranes from a thin, fragile retina.
32.4Subretinal Membranes/Strands
32.4.1 PVR and PDR
Not all subretinal membranes cause retinal detachment or prevent reattachment. Since a retinal break must exist to access them, the surgeon should not to be tempted to remove a subretinal membrane just because it is there (see Sect. 8.1). If the membrane does need to be removed, keep in mind the following.
•Complete the vitrectomy, paying special attention that a complete PVD has been created.
•Before dealing with the subretinal membranes, always make sure no epiretinal membrane is left behind. This is especially crucial if an access retinotomy needs to be created.
52 Posterior cortical vitreous.
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•Not everything that looks to be a subretinal strand is indeed one: retinal folds can give the same appearance. The folds, however, disappear if the retina is reattached or pushed, see below.
•Evaluate the number, location, and strength of the membranes. The latter is assessed by pushing on them with the probe’s blunt tip and noting the retina’s mobility over the strand; the air-test is also useful.
–If multiple membranes at multiple locations (see Fig. 32.15) need to be removed, consider mixing the gauges: use a 20 g subretinal forceps with a long reach (see Fig. 32.16) so that the minimal number of retinotomies is needed to provide access all membranes.
–If there are multiple membranes at multiple locations and you are using MIVS, you will need multiple retinotomies.
Fig. 32.15 Subretinal proliferation. Extensive subretinal proliferation following 360° retinectomy (see Sect. 33.1) for a total RD and retinal incarceration. Unless a 20 g subretinal forceps is used, it is impossible to remove all membranes through a single retinotomy
Pearl
Horizontal forceps is preferred to vertical ones because the jaws do not have to be inserted between the retina and membrane in order to grab the membrane.
•To perform the retinotomy, select a site that:
–Is rather far from major vessels.
–Provides access to the membrane so that the forceps can be held in your dominant hand.
–Is right over the membrane.53 This also overcomes the unexpected difficulty when the membrane is further away from the retinotomy and is difficult to grab: even though its exact location was very obvious before the forceps was inserted into the subretinal space, once the retina is somewhat lifted with the forceps, the membrane “disappears” (see below).
53 The forceps blades are too short to reach the membrane otherwise. With 20 g surgery and use of the proper subretinal forceps such as the 1286.0 model from DORC (Zuidland, the Netherlands; see Fig. 32.16), the retinotomy need not be right over the membrane.
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Fig. 32.16 A 20 g subretinal forceps. (a) Overview of the 20 g instrument. (b) Close-up of the blades
•Apply a diathermy spot at this location.
–The diathermy eliminates the risk of hemorrhage and possibly helps create the postoperative chorioretinal adhesion.
•Grab the membrane and slightly pull it up. Never pull the membrane simply upward; this can put excessive traction on the retina.
–Change the vector so that the membrane is stretched toward its endpoint in one direction (see Fig. 32.17).
–Once the membrane is liberated in that direction, change the vector of pulling toward the opposite direction until the separation is complete there.
–Never lose sight of what is happening at the membrane’s far end54 where it is separating from the retina. Occasionally the adhesion between them may be so strong that the membrane tears the retina and drags the retina underneath itself.
–Occasionally, the membrane’s strong adhesion is not to the retina but the choroid: as the surgeon pulls on the strand, it detaches the choroid. Simply stop the maneuver and cut the strand; the choroid will readhere (see Sect. 54.5.2.2).
–If the adhesion between the retina and membrane is too strong and the membrane breaks at a location too far from the retinotomy for the forceps to regrab it through the same retinotomy, there is a high chance that this is still sufficient to eliminate the traction the membrane had caused. The air-test will determine whether this is indeed the case (see Sect. 31.1.2).
54 This is one of the many reasons to view the entire process through the BIOM.
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Fig. 32.17 Removal of a subretinal membrane. (The illustration is showing a retinotomy that is right above the membrane; as mentioned in the text, this location allows the use of any type of forceps.) (a–d) Schematic representation. (a) The forceps is approaching the membrane; the retinotomy has already been prepared. (b) The membrane is grabbed and pulled; the movement’s vector is a combination of an upward and a retina-parallel movement, along the axis of the membrane in one direction. (c) Once the membrane is freed from the retina in the direction opposite of the previous pull, the direction of pulling is changed 180°. (d) Once the membrane is free in both directions, it is pulled up and removed. (e–f) Clinical examples. (e) The retinotomy has been created right over the subretinal membrane, which is grabbed by a serrated forceps and lifted. (f) The membrane is pulled in a close-to-retina-parallel direction on one side; it will be turned 180° and pulled in the other direction. This minimizes the traction on the retina and allows much more control than a simple pulling-up motion [i.e., as if continuing with the movement seen on (e); see the text for more details.] F forceps, R retina, M membrane
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Q&A
QIf the membrane is rather far from the retinotomy site, how easy is it to grab it?
AIt is not easy and not without risk. First, the visibility of the membrane dramatically drops once the retina is somewhat lifted by the forceps. What was “clearly there” before all of a sudden disappears (see above). Second, as the surgeon is struggling to find the membrane, he may injure the choroid accidentally and cause a major hemorrhage. Third, the retinotomy may get significantly enlarged.
•The membrane may be very long, requiring it to be pulled-regrabbed several times to entirely lift it into the vitreous cavity. Alternatively, the forceps can be spun as if it were a fork to eat spaghetti or a bimanual technique employed with two forceps.
•Once the membrane causing the RD is removed, a F-A-X is carried out, and the surgeon must decide whether to laser the central retinotomy (see Sect. 30.3.1).
•If there are numerous membranes in multiple locations, a retinectomy, rather than multiple retinotomies, may be the preferable option.
– Make sure the inner retinal surface is free of membranes.
– Do a retinectomy (see Sect. 33.1).
– Flip the retina over, take a crocodile forceps, and try to grab all obvious membranes.
Pearl
What appeared so obvious to be a subretinal membrane when viewed in the retina’s normal position becomes much less so once the retina is flipped. It may be necessary to turn the retina over and back several times to identify all membranes. Also, it is not that difficult to grab too deep and engage the retina proper; the more parallel with the retina the forceps is held, the smaller the risk of this complication. Some of what looked like focal strands before will turn out to be true membranes, covering a much larger area.
–Not all membranes need to be removed since some of them are not strong or elastic enough to cause an RD (see above, air-test).
32.4.2 CNV
Surgical removal of such membranes is still performed occasionally, even though this procedure is largely replaced by anti-VEGF injections today.
•The surgeon is in full control how he removes the membrane. He has, however, no control over whether he also removes a large part of the adjacent RPE or
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causes a major bleeding (see Table 40.1). The risk of bleeding is reduced, but not eliminated, by repeated anti-VEGF therapy administered in the weeks prior to surgery.
–The patient has to understand these and accept the risks.
–OCT helps in determining whether the membrane is under or over the RPE; membranes that are underneath pose a much higher risk of ripping the RPE, which would result in a stable condition but a large central scotoma.
32.5Membranes Over the Ciliary Body55
In eyes with anterior proliferative disease or after trauma with significant PVR risk, it is crucial to thoroughly clean the surface of the ciliary processes. Failure to do so, and do so early, is a huge risk factor for postoperative hypotony.
•Remove the lens and the capsules (see Sect. 38.5).
–No IOL is to be implanted until the PVR risk is over.
–IOL implantation is indicated only if the visual function justifies it. If there is visual potential, implant an iris-claw lens.
•Do self-indentation.56
•Use various instruments (probe, scissors, forceps, spatula etc. – but never a scraper) to lift vitreous, fibrin, blood, membranes etc., off the surface so that the ciliary processes are completely free.
–Switch hands and repeat the maneuvers 360°.
•There are two major risks with the procedure:
–Bleeding if the ciliary process is damaged by a sharp tool. The bleeding is profuse and difficult to stop. The diathermy must be applied “blindly,” inevitably damaging a rather large area (see Table 40.1).
–Pulling off the ciliary body with a blunt tool. If the ciliary body detachment is longer than ~2 clock hours, it should be sutured back into place.
32.6Cutting Epiretinal Membranes with Scissors57
Below are a few suggestions for the use of scissors, as opposed to forceps or the probe, to deal with epiretinal membranes.
• The most versatile type of scissors is the vertical one.
55This is an indication where the superiority of EAV is unquestionable.
56This is a rather time-consuming procedure where perfect coordination of the indentation and intraocular maneuvers is necessary; it is virtually impossible to achieve such coordination if someone else does the indentation. This is true even though self-indentation makes bimanual surgery impossible.
57See also Sect. 13.2.1.4.
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•Ideally, the tip of the blade should show at the far end of the membrane before any cut is made. This reduces the risk that retina, which may be very adherent to the membrane, is also cut.
•Once the blade is inserted between the membrane and retina, it can be used as a spatula (see Fig. 32.18).
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Fig. 32.18 Schematic representation of using the scissors as a spatula in separating an epiretinal membrane from the retina. (a) The forceps’ lower blade is inserted underneath the membrane so that the tip of the blade is past the membrane’s far edge. The membrane is not cut; instead, the surgeon moves the blade (double arrow) in a retina-parallel plane to sever the adhesions between the two tissues – although he is not able to actually see the adhesion points. Surgeon’s view. (b) The adhesions serve as anchor points so that the two tissues remain locked together until the last of the adhesions is broken; for this reason, the surgeon should try to move the forceps in both directions alternatively, not “go all the way” in one direction first. Should he do that or cut the membrane, the maneuver becomes impossible to execute. Cross-sectional view. The concept is identical to that seen in Fig. 13.10; the advantage of using scissors, as opposed to a spatula, is that if the adhesion proves to be strong, cutting instantly becomes possible, without the need to exchange the tool. Alternatively to inserting the lower blade under the membrane, insert both blades with the scissors in closed position. R retina, M membrane, F forceps, A adhesion point
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Pearl
If the membrane is cut, the “spatula” option for the forceps is no longer available since the anchors that are needed for spatula-action are removed.
•If the membrane is vascularized,58 it will bleed when cut. Use diathermy to close the vessel(s) but keep in mind that it is often not possible to establish from which direction the blood vessel is fed; it is best to cauterize the adjacent area in both directions.
–Remember that the diathermy causes shrinkage as well; it may become more difficult to insert the blade under the membrane.
•Never forget the carpenter’s rule: measure twice before cutting once.
•Do not try to cut a subretinal membrane unless it is so adherent that it wants to turn the retina underneath itself when the membrane is pulled (see above).
58 Except when it becomes a “ghost” vessel due to the anti-VEGF injection.