52.1.2 Preoperative Considerations

•Panretinal laser treatment should be performed in all eyes with proliferative disease.2

–Once you have TRD, only areas without membranes3 should be treated, to avoid causing iatrogenic contraction of the tractional membranes.

•Intravitreal anti-VEGF medication (bevacizumab) should be injected 2–3 days preoperatively.

–The main goal is to reduce the risk of intraoperative bleeding, but the drug also makes separation of the proliferative membrane from the retina easier.

–To avoid a rebound effect after the injection, the patient must be warned that the operation must take place as scheduled. If for whatever reason it has to be postponed, the injection should be repeated every week or so until the surgery can go ahead.

–Monitoring the patient’s systemic condition (glycemic control, blood pressure etc.) is a crucial part of the management.

•Commonly, the indication for surgery is a combination of TRD, ME, and VH. The patient must be advised that any of these may recur, even if surgery was a complete success. The VH is especially prone to recurring, even if no treatable pathology is present (see Sect. 35.4.3.2).

Pearl

The diseased vessel wall is the reason for VH in eyes with diabetic retinopathy. Even in the absence of neovascularization, the vessel may be unable to resist the elevated blood pressure, explaining why the rebleeding frequently occurs shortly after waking up. Such a “morning hemorrhage” may occur even if the blood pressure is well controlled.

52.2Surgical Technique

Much of this has been described in Sect. 32.3.2; only certain aspects of the surgery are discussed here.

The typical appearance of the posterior segment in an eye with PDR is a relatively spared macula,4 which is surrounded by thick white membranes along the

2My personal experience taught me to consider such panretinal treatment early in progressive nonproliferative disease.

3And, obviously, attached retina.

4The macula is covered by a fine epiretinal membrane (which is usually the nondetached posterior hyaloid face), but spared by the thick, white, vasoproliferative membrane.

major vessels. This membrane may be vascularized and at certain spots have strong adhesions to the retina. Depending the contractile properties of the membranes, TRD and secondary retinal breaks can develop (see Chap. 55). The membrane often blocks the actual visualization of the TRD.

Intraoperatively the first thing the surgeon has to decide is the order of attack. The technical option I have found most useful is described below.

•Make an opening in the central area, above the macula, to release the traction on the macula as well as the tangential force acting upon the major adhesion line, along the vascular arcades.

•Cut 360° into the thick, white membrane (see Fig. 52.1), anterior to the vascular arcades; this will separate the major proliferations from the rest of the vitreous and retina and help reduce the traction both on the anterior and posterior retina.

–Remember that you are almost always dealing with a vitreoschisis. The tissue you just cut is the anterior wall of the schisis cavity.

Fig. 52.1 Schematic representation of the proliferative membranes causing TRD in an eye with PDR. The retina (red line) is partially detached from the eyewall (thick black line). The traction is exerted primarily by the centrally located proliferative membrane (thick blue line), which maintains some distance from the retina at most locations. This membrane causes a mostly P-A traction. However, another tractional force (thin blue line) is also present, even if this is much less conspicuous to the surgeon. This membrane causes a mostly tangential traction. Representing the still-attached posterior cortical vitreous, this membrane is very adherent to the retina, and the thick proliferative membrane reinserts into it anteriorly. Several vitreoschisis cavities are thus formed. The arrows show the initial location where the separation of the proliferative membranes from the retina would take place. If the macula (blue star) were also involved in the detachment, the initial step would be to separate it so that the inevitable traction exerted during surgery will not involve it. More details are provided in the text

•Extend the vitreous removal all the way to the periphery. With scleral indentation, complete the vitreous removal at the base.

– This still leaves the cortical vitreous on the retina; see below.

•Also remove the anterior hyaloid face.

•Return to the posterior retina and deal with the thick, white proliferative tissue: delamination or segmentation, using various instruments.

•Also consider removing the ILM, even if the macula is dry.6

–If the macula is edematous, the ILM is commonly very adherent in these eyes (see Sect. 49.2).

–I do not peel the ILM if the retina is ischemic and thin.

•Complete the operation with gas or silicone oil tamponade. The latter has the advantage of preventing the VH from recurring.

There are some additional issues to keep in mind.

•In certain locations it may be impossible to separate the membrane from the retina. Make sure to completely circumscribe the remaining white stalk so that it does cause traction in the future.

–If the ILM has extreme adherence to the retina, exerting strong traction, abandon the peeling.

Pearl

Cutting a membrane that is very adherent to the retina requires the use of scissors, usually retina-parallel or curved; these are not easy to manipulate without undue risk of pushing their sharp tip into the retina and choroid. An easier technique is offered by the probe; the surgeon should activate the cutting first, before being close to the membrane, and use low aspiration/flow when he approaches the membrane.

•If a retinal break is also present,7 the risk of postoperative RD increases: the more the retina is liberated from the tractional forces, the worse the risk.

–The creation of iatrogenic retinal breaks, although far from ideal, may still be preferable to leaving traction behind. In case of a break it is of utmost importance to remove all tractional forces.

•If a large retinal break is present or retinectomy is needed, consider prophylactic chorioretinectomy to reduce the risk of PVR development (see Sect. 33.3).

•Consider silicone oil implantion (see Sect. 35.4) to achieve/maintain retinal attachment and/or prevent (recurring) VH (see Sect. 62.4).

6See also Sect. 49.2.

7Whether it has been there preoperatively or created during surgery.