27.2How Much Vitreous to Remove?

Just as important as the question of how to remove the vitreous is how much to remove. The range stretches from “nonvitrectomizing” to “complete” PPV2 (see

Fig. 27.1 and Table 27.2).

Fig. 27.1 Schematic representation of classifying the extent of vitreous removal. This is a personal, somewhat arbitrary, and not objectively measurable/verifiable attempt at distinction. The numbers represent percentages: 0%, nonvitrectomizing; 10%, minimal; 30%, core; 50%, semitotal; 80%, subtotal; 100%, total or complete (see Table 27.2 for more details)

Table 27.2 Classifying the amount of vitreous to be removed

aThe indications shown here represent an incomplete list.

bThe opposite of what has been suggested, highly controversially, in the Endophthalmitis Vitrectomy Study.

cA more appropriate term would be “a sausage of vitreous”. dThe anterior vitreous face is also retained.

2 As one of my teachers, a pioneering giant in the field, Relja Zivojnovic, so eloquently described: “Vitrectomy is done when the vitreous is gone.”

It is impossible to give blanket advice regarding the amount of vitreous that needs to be removed. It is influenced by several factors such as the etiology (indication), the condition of the vitreous, the VR interface, and the vitrectomy equipment (see Sect. 12.1). Below are a few general considerations; more details are found in

Part V.

•For most surgeons, the primary factor determining how much vitreous he intends to remove in a particular case is the etiology. However, certain aspects of the perivitreal anatomy must also be taken into account. Only a brief summary of what was detailed in Chap. 26 is provided here.

–Posterior to the equator, a healthy vitreous is mildly adherent to the retina, but separation is generally possible (see Sect. 26.1.2).3 The preoperative diagnosis of PVD is always uncertain; often a vitreoschisis is found intraoperatively (see below and Fig. 26.2).

Q&A

QIs it always possible to achieve vitreoretinal separation in the posterior pole?

ANo. In young patients, even a limited “truly posterior” PVD may be too risky. In certain conditions such as high myopia, creating a PVD can also be very difficult. More peripherally, just the recognition of the presence of a still-attached cortical vitreous can be a challenge. In diseases such as RD, PDR, or VMTS, the 2 tissues may be inseparable anterior to the equator or even posterior to it (see below).

–At and anterior to the equator, the adherence between the two tissues may be weak, strong, or impossible to break.

–At the vitreous base,4 any attempt to create a PVD leads to the formation of retinal tears.

–In young patients, the vitreous cannot be separated from the lens capsule, even if surgical detachment of the anterior vitreous face would be required.5 The capsulovitreal adhesion eventually disappears with age.6

3In children pharmacological vitreolysis may play a crucial role since safe surgical PVD is often impossible. However, the drug is currently very expensive and has a limited success rate.

4Scleral indentation is necessary; the surgeon should follow a certain routine to make sure that he does a complete job (see Sect. 28.5).

5Such as RD, PDR, PVR.

6The only area where the strength of the VR adhesion does not weaken with age is the vitreous base.

–Abnormal VR adhesions may be present at any location; the surgeon must always proceed cautiously so as to avoid damaging the retina by too fast or aggressive attempts of separation.

Pearl

If there is a vitreous-related complication following vitrectomy, it comes from vitreous that has not been removed.

•I do not perform nonvitrectomizing vitrectomy: I always try to create a PVD. Leaving cortical vitreous on the macula often leads to subsequent complications such as EMP development.

•In most macular indications, no untoward consequences are to be expected even if only minimal or core vitrectomy is performed.

•When the vitreous is a healthy gel (e.g., no floaters or traction), it is tempting to leave much of it behind. However, postoperative structural changes such as liquefaction and mouches volantes typically occur.7 The patient, noticing the mobile object/s casting bothersome shadow on the retina, may attribute their presence to a surgery that was suboptimal.

Pearl

The default plan for PPV therefore should be a complete vitrectomy. In most cases, however, this is not necessary, and a less-than-total vitrectomy will suffice – but the surgeon must make a conscious decision why not to remove all or most of the gel in the particular case.

•If traction8 is present, as-complete-as-possible vitreous removal is called for to reduce the risk of retinal tears developing postoperatively. Conversely, tractionelimination itself risks causing iatrogenic retinal tears intraoperatively. In such cases, the surgeon needs to decide which is the risk that he considers greater: carrying on with the PVD (intraoperative complications9 may arise) or abandoning it (postoperative complications10 may arise).

7Another consequence of a less-than-complete PPV is increased mobility of the remaining vitreous, which increases the risk of RD development (see Sect. 54.5.2.2).

8In RD, PDR, PVR, VMTS etc.

9Retinal breaks, RD.

10RD, PVR.