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Ординатура / Офтальмология / Учебные материалы / Vitreoretinal Surgery Farenc Kuhn Springer.pdf
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244

27 The Basics of Vitreous Removal

 

 

27.3Recognizing the Presence of the Vitreous Gel

The surgeon’s job is not made easier by the fact that the normal vitreous is basically invisible. Manipulating the angle of endoillumination is helpful to a certain extent (see Sect. 22.2), but it is best to use some type of “visual aid” to identify whether vitreous is present.

Q&A

Q What if the surgeon finds that an eye contains very little vitreous?

AIf the vitreous removal is completed much more rapidly than usual, it typically means that most of it is still attached to the retina (hence the rationale for P-A PPV, see below). TA should be used, a PVD created, then the remaining vitreous can be removed.

27.3.1 Mechanical Aids

With BSS infusing the vitreous cavity, the gel hydrates.

During surgery the vitreous becomes increasingly recognizable. This phenomenon is barely conspicuous over the posterior pole but makes completing the vitreous removal in the periphery easier once the other tasks (e.g., EMP removal) are finished.

Even if the vitreous itself is not visible, a mobile shadow from the edge of the gel11 as the probe “bites” into it may appear as a snaking dark line dancing on the retinal surface below.

In eyes with poor circulation or a very structured gel, pushing the probe into the vitreous cushion causes the retina underneath to whiten.

If the retina is detached, it is crucial to determine whether vitreous is still adherent to it.12

Aspiration, even if the probe is at some distance from the retina, results in the retina moving toward the probe if vitreous is engaged, and no movement if only BSS is present.

When the probe is moved toward the retina, it will push it away if vitreous is present. In the absence of the vitreous cushion, no retinal movement is seen.

In almost all eyes with PDR, a vitreoschisis is present (not a PVD), mostly anterior to the equator. Its thin outer wall13 is so adherent to the retina that aspirating it can detach a previously attached retina. This is obviously not a recommended method to show the presence of the vitreous (see Sect. 52.2).

11i.e., at the border of gel and BSS.

12The use of the probe is described here, but the surest way is to inject TA (see Sect. 34.1).

13The outer wall of the schisis cavity is vitreous but behaves like a true membrane.

27.3 Recognizing the Presence of the Vitreous Gel

245

 

 

27.3.2 Air (Pneumovitrectomy)

Air allows visualization of the remaining vitreous “skirt” at the base (see Sect. 14.1 and Fig. 27.2)14 while also reducing the risk of biting into the retina as the air pushes it against the RPE.

Perform an F-A-X.

For the purpose of pneumovitrectomy, the drainage of the fluid need not be complete.

Adjust the BIOM front lens so that you have the best possible visibility (see

Table 16.5).

The vitreous is invisible until you push the probe into it. The change in the light reflex clearly shows that vitreous is present. How close to the retina you can shave the gel depends on the angle between the probe’s shaft and the retina (see

Fig. 24.1).

a

Fig. 27.2 Pneumovitrectomy.

(a) The probe is close to the

retina in the periphery; the eye b is filled with air and the probe

is kept in air. The view of both the probe’s tip and the retina is rather clear and no unusual light reflex is seen. (b) The probe is being held in the same area, but its tip is now immersed in gel vitreous. A light reflex appears around the tip and the image of the probe’s distal part is slightly distorted. Once the vitreous has been removed or the probe withdrawn into air, the image reverts back to that seen on (a)

14 Air is also able to demonstrate the presence of vitreous behind the lens (see below, Sect. 27.5.3).

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