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Ординатура / Офтальмология / Учебные материалы / Vitreoretinal Surgery Farenc Kuhn Springer.pdf
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Materials and Their Use

14

 

14.1Air1

Air is a great intraoperative tool for several reasons:

It forces to the deepest point of the eye the intravitreal/subretinal fluid, allowing its drainage.

It provides instant tamponade for a retinal break.2

It keeps the retina attached, even if the IPM has been broken.

Once the probe is submerged in it, air allows visualization3 and safe removal of the (peripheral) vitreous. The air pushes the retina against the RPE and thus permits gel removal even in areas of very strong VR adhesion (pneumovitrectomy, see Sect. 27.3.2).

It acts as a lens, providing the surgeon a wider field of view than under fluid.

In the AC, it has the following benefits:

Instant deepening of the AC.

Prevention of the formation of anterior synechia.

Highlighting the presence of prolapsed vitreous4.

Air helps demonstrate the presence of vitreous behind the posterior capsule (see

Sect. 27.5.3).

1Additional information about most of these materials is found in Chap. 35.

2In RD surgery, the tamponading effect of the gaseous material is less important than its spaceoccupying function (see Sect. 54.5.2.6). The benefit of the air (gas) is that it prevents the shearing effect of the intravitreal fluid on the retinal edge around the break.

3Air thus acts as a diagnostic tool so that the surgeon can detect the presence of residual vitreous. The “skirt” of peripheral vitreous is typically invisible in BSS, even under air. However, once an instrument, such as the probe, is submerged in the vitreous skirt under air, the light reflex immediately changes and the parallaxis becomes more evident (see Figs. 14.1 and 27.2).

4The normally symmetrical/even shape of the air bubble is deformed where the vitreous “cuts” into it.

© Springer International Publishing Switzerland 2016

115

F. Kuhn, Vitreoretinal Surgery: Strategies and Tactics,

DOI 10.1007/978-3-319-19479-0_14

116

14 Materials and Their Use

 

 

Complications5: When A-F X is performed in the presence of RD, there is a danger of small air bubbles (“fish eggs”) getting under the retina or the air tearing a retina that is under severe traction or is shortened (similar to that seen with gas use, see Sect. 54.4.2.9).

The risk of high IOP or cataract is less pronounced with air than with gas (see below) because it is nonexpansile and gets absorbed in a few days.

Pearl

A rarely mentioned side effect of the use of intravitreal air and gas is that most patients cannot see through them. If they are not told about this in advance, it may be a very scary experience – another example of the importance of proper counseling (see Chap. 5).

14.2Intravitreal Gas

Gases are used to provide tamponade that lasts several days to a few weeks.

Depending on their concentration, gases can be nonexpansile or expansile. They are assumed to work via their tamponading effect (“covering the retinal break”) in eyes with an RD (see the remark above) or macular hole.

SF6: It doubles its volume if pure gas is used. The typical concentration is ~30%, which lasts for up to 2 weeks.

C3F8: It increases its volume 4 times if pure gas is used. The typical concentration is ~15%, which lasts for up to 2 months.6

With the patient being at reduced atmospheric pressure,7 even a gas with a nonexpansile concentration expands, and this effect is proportional to the outside pressure; IOP elevation results.

Such an IOP elevation would also occur during general anesthesia as the N2O used enters the vitreous cavity. The vitrectomy machine prevents this pressure rise by automatically adjusting the IOP, but if the anesthetic gas is not allowed to escape8 from the vitreous before surgery is completed, the gas tamponade will be short-lasting because that gas escape occurs postoperatively.

Gases can also be used in the AC in eyes with severe hypotony. They increase the IOP for a few days if a nonexpansile, or even weeks if expansile, concentration is used.

5Only selected complications are mentioned in this chapter.

6I do not use this gas at all: if longer-term tamponade is necessary, I prefer silicone oil.

7Such as flying or being on a mountain.

8This typically requires ~10 min.

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