27.3.3 Stains and Markers

•Blood is a natural stain,15 allowing the visualization of the gel after vitreous hemorrhage.

•Intravenously injected sodium fluorescein stains the vitreous after a few minutes and persists for a few hours.16

•ICG gives the vitreous a faint greenish discoloration (see Fig. 34.1).17

•The most effective weapon in the surgeon’s armamentarium is TA (see Sect. 34.1), whether aiding in the creation of a PVD or allowing the visualization of vitreous elsewhere.

27.4The Sequence of Vitreous Removal

There is no absolute rule; my default option is the P-A approach.

•A small amount of vitreous is removed from over the maculopapillary area.

•~0.1 ml of TA is injected into this artificial lacuna (see Fig. 34.2).

Pearl

Do not inject more than this miniscule amount of TA. A thick coat of TA makes the PVD risky since the surgeon is unable to see the retina beneath and may push the probe into the retina or scratch it if he uses a sharp tool. The appearance of a retinal hemorrhage indicates that this has happened.

•If the vitreous cortex is still adherent to the posterior pole, a PVD is created (see below).

–Remember that the proximal vitreous surface may be smooth, in which case the crystals do not adhere to it, giving the false impression that a PVD is present (see Table 26.1).

–How far anterior the separation is carried depends on the indication and the conditions in the particular eye (see above).

•The central vitreous is removed.

•If indicated, the peripheral vitreous is removed/shaved using scleral indentation (see Chap. 28). TA may be used to identify the vitreous remaining on the retinal surface.

Pearl

When working in the periphery, use low magnification: since the BIOM front lens is close to the cornea, even a small movement of the eyeball will result in loss of the image.

15Obviously, intraoperative blood injection is not used in clinical practice.

16Fluorescein to stain the vitreous is not used in clinical practice.

17Since the dye does not penetrate into the vitreous, it is not used purposefully to stain the gel, except in the highly myopic eye with otherwise little contrast due to the loss of pigment (see Sect. 56.2).

•If indicated, the anterior hyaloid face is also removed; in the pseudophakic eye, a posterior capsule is also performed.

There are important exceptions to the P-A approach.

•Opaque vitreous. If the retina is not visible due to blood, pus, synchysis etc., meticulous anteroposterior vitreous removal is recommended.

•Presence of severe macular traction in diseases such as VMTS, PDR, and PVR. The selected sequence is based on the particulars of the case and how well TA can show the traction forces.

Q&A

Q What are the advantages of the P-A sequence of vitreous removal?

A In principle, the further away the probe from the retina, the safer the vitrectomy and the faster it can be completed. In addition, it is easier to create a PVD when the posterior hyaloid face is still unbroken.

27.5The Technique of Vitreous Removal18

27.5.1 PVD

As mentioned earlier, the presence of a Weiss ring (see Fig. 27.3) means nothing more than VR separation at the disc. TA still should be used to determine whether PVD must be created (see above). The separation should be started at the temporal side of the disc.

Fig. 27.3 Weiss ring. The vitreous has separated from the retina at the disc margin, allowing a ring of fibrous tissue to be seen in the vitreous cavity; the shadow of the ring is also visible on the retinal surface

18 Vitrectomy at the base is described in Chap. 28; gel removal in the central area of the vitreous cavity requires no specific comments except what has been presented in Chap. 24.

Q&A

QWhy not start the PVD on the nasal side of the disc where any iatrogenic damage to the nerve fibers has less serious consequences?

ABecause the PVD should be fairly symmetrically extended as it approaches the equator, and the retinal area temporal to the disc is larger.

If using aspiration only, do the following:

•Turn the probe sideways.

•Advance the probe just enough so that it barely touches the retinal surface.

•Start at the inferotemporal margin of the disc.

•Wait a few seconds for the port to engage the vitreous coating the retina. Use maximal aspiration but no cutting (see Table 12.2 for the standard settings of the vitrectomy machine).

•Move the probe toward 12 o’clock along the disc edge on the temporal side until the vitreous is lifted from the retinal surface.19

•You may also use a barbed needle (see Sect. 13.2.3.1) to engage and then elevate the vitreous the same way. Unless too much TA is on the retinal surface, the depth of the needle’s hook is clearly visible, and retinal damage can be avoided. Once the vitreous is lifted, switch to the probe.

•Extend the PVD carefully toward the periphery, but stop roughly at the equator to avoid the creation of retinal tears. In most eyes, the PVD may be carried a little more anteriorly (see Chapters in Part V); in some diseases,20 it is highly advisable to do so.

27.5.2 Vitrectomy Anterior to the Equator

•If the vitreous separates from the retina easily and without tearing it, and you consider it important to carry the PVD more toward the periphery, carefully do so.

•If the separation is difficult and you consider it essential to continue toward the vitreous base with the PVD but the two tissues are inseparable and retina starts to tear, you have two options (see the dilemma above, Sect. 27.2).

–Stop with the PVD and shave the gel in the periphery instead; shave it as close to the retina as possible.

19This is actually a dangerous moment for the less experienced surgeon. Being content to see the PVD occurring, he may get carried away and extend the separation far too anteriorly – a common error until patients with postoperative RD accumulate and the cause of the RDs is identified.

20Such as RD, RDP, PVR, and retinoschisis. See Part V for more details.

–If it is deemed essential to not leave any vitreous behind, choose retinotomy/ retinectomy (see Chap. 33). The main indications for such a somewhat drastic measure are PVR, occasionally RD and PDR (see Chaps. 52, 53, and 54).

27.5.3 Vitrectomy Behind the Lens

In the pseudophakic eye, this is technically easy, and cutting into the iris is the only risk.21

If the eye is phakic, the lens is not completely clear, and the surgeon decides against simultaneously removing the cataract, the somewhat opacified posterior capsule may help in delineating the border between it and the anterior vitreous face. Nonetheless, even in these cases but especially if the lens is clear, it is safer to do the following:

•Swing out the BIOM and use the microscope’s illumination at relatively high magnification.

•Inject a few small air bubbles behind the lens.

–If there is no vitreous present, the air bubbles will migrate toward the equator of the lens.22

–If vitreous is present, the air bubbles are trapped behind the lens and give a good approximation regarding the location of the posterior capsule.

•Reintroduce the probe, focus the view through the microscope slightly behind the air bubbles, and aspirate/cut while keeping the probe behind the air bubbles the entire time; once the vitreous is removed, the air bubbles move out of the visual axis.

Pearl

If the eye is aphakic, performing anterior vitrectomy has a high risk of biting into the iris since the gel is commonly very adherent to both iris surfaces. Turn the port sideways (never toward the iris) and increase the vacuum/flow only gradually.

21Remember to also make a posterior capsulectomy.

22A higher plane than the lens’ posterior pole.