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Pits & Pearls
PFCL-silicone oil exchange: It is ideal to remove all water from the posterior segment at the beginning of the PFCL-silicone oil exchange. To achieve this, push the infusion inwards with your hand just when you start to infuse the silicone oil – the inner opening of the infusion port should almost touch the anterior surface of the intraocular PFCL bubble. Silicone oil and PFCL ‘like’ each other and will stick together. If you now continue to infuse the silicone oil, the oil will form a layer on top of the PFCL and will displace the intraocular water out through the sclerotomies despite being lighter than water. As soon as you see silicone oil reaching the trocars, temporarily interrupt the infusion and switch to intraocular view with the light fiber and fluid needle. Remark: For this method you need trocars without valves.
Continue at step 14.
12. PFCL/air exchange
If the shaving is finished, a PFCL-air exchange is performed. Before we perform this procedure, we have to look at Diagram 10.3, to get a better sense of the situation
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Intraoperatively |
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postoperatively |
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PFCL / air exchange |
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before |
during |
after |
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water |
air |
air /gas |
gas |
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water |
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PFCL |
PFCL |
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water |
Diagram 10.3 Diagram of the location of fluids during the PFCL/air exchange
in the vitreous cavity. Before the PFCL-air exchange, the vitreous cavity is filled with PFCL and on top of it is a layer of water. During the PFCL/air exchange, there is an anterior phase of air, a middle phase of water and a posterior phase of PFCL. After the PFCL/air exchange, only air is in the eye, which is then replaced by gas. Postoperatively, water will accumulate again under the gas phase. Consequently, the gas does not effectively tamponade the posterior or inferior retina.
The PFCL-air exchange is certainly the most difficult and most important manoeuvre in detachment surgery, mainly because visibility under air is poor (Figs. 10.11 and 10.12). Therefore, it is essential to understand the characteristics of PFCL and air. PFCL and air ‘work’ as antagonists. Air exerts a pressure in the eye from peripheral (anterior) to central (posterior) but PFCL vice versa from central to peripheral (Fig. 2.23).
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Fig. 10.11 Drawing of the situation in the eye during a PFCL for/against air exchange. The water phase, which is located between the air and PFCL phase, is being aspirated
Fluid
needle
Water
Air
PFCL
cmolter
Fig. 10.12 Same procedure as in Fig. 10.11. The tip of the fluid needle is held just above the PFCL bubble in order to remove the water phase
PFCL presses most of the subretinal fluid from the central pole to the periphery through the retinal break into the vitreous cavity, but a part of it flows beyond the break up to the ora serrata, where it cannot be aspirated (‘trapped fluid’). This ‘trapped fluid’ can, however, be removed with air: The air attaches the retina beginning in the periphery and ending at the central pole, and thereby pushes the ‘trapped fluid’ in the direction of the break.
How do we proceed in practice? Before you switch to air, hold the fluid tip in the middle of the break. If necessary, take the scleral depressor to help. If several breaks are present, start with the most peripherally located break and then move to the next
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Fig. 10.13 Drawing of a sandwich technique. The air pushes the subretinal fluid towards the posterior pole. PFCL prevents that the subretinal fluid proceeds to the posterior pole. Both meniscus of air and PFCL must meet at the break in order to drain the subretinal fluid from here. Remember: Air pushes trapped fluid to the centre, and PFCL pushes trapped fluid to the periphery
Fluid |
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needle |
Air |
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PFCL
cmolter
more central break. Now, the scrub nurse switches the three-way tap from water to air. In the beginning, disturbing air bubbles arise and the view deteriorates. Remain calm and turn the front lens with the BIOM-focus wheel up. The visibility will gradually improve.
In the beginning, the break is covered with PFCL. After a short time, the PFCL is suctioned to the posterior edge of the break. Now the air presses the subretinal fluid in the direction of the break (Fig. 10.13). The subretinal fluid is trapped between anterior located air and posterior located PFCL, so-called sandwich tamponade. Now you aspirate the subretinal fluid through the break and at the same time the water phase between air and PFCL (Fig.. 10.14).
Only when the ‘trapped fluid’ and the water phase in the vitreous cavity are completely aspirated can you continue to aspirate PFCL beyond the posterior edge of the break. This is very important because the subretinal fluid, which you do not aspirate, will continue to flow beyond the break in the direction of the optic disc.
If the ‘trapped fluid’ is completely removed, you switch with the fluid needle alternately between the PFCL bubble in order to reduce it and the break in order to aspirate fluid here. Try to aspirate without indenting the break. But sometimes you can only reach the break with the fluid needle if you indent it with the scleral depressor. But you should not indent the break itself, but the retina on either side of the break. By indenting the break, you close it and prevent the aspiration of subretinal fluid. This procedure is usually not easy and requires patience.
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Fig. 10.14 Same procedure as in Fig. 10.13. Hold the tip of the fluid needle in the middle of the break and drain the subretinal fluid and residual intravitreal fluid. Do not aspirate PFCL before you completely removed the subretinal fluid
The remaining PFCL is aspirated by holding the fluid tip directly in front of the optic disc. Make sure that the PFCL is completely removed, and that neither the retina nor the optic disc is affected.
If after complete removal of PFCL, residual subretinal fluid remains at the posterior pole, then you may either inject PFCL again up to the break and aspirate the fluid or – if it is only a small amount – leave it. With a postoperative prone position (face down), the subretinal fluid will be absorbed on the first postoperative day.
Important: If the retina is attached under air in detachment surgery, then it will also later be attached under silicone oil or gas. Why? When the retina is completely attached under air, you have drained the subretinal fluid completely. Air presses the entire subretinal fluid from the periphery to the optic disc, where it is easy to spot.
This is only partly true for PFCL because PFCL pushes the subretinal fluid from the posterior pole to the periphery, where the ‘trapped fluid’ is difficult to detect.
The fluid/air exchange is therefore the crucial test for successful retinal detachment surgery (attached retina).
Pits & Pearls No. 55
Removal of PFCL: Two pearls for PFCL removal: (1) When using a silicone tip-fluid needle, the risk of retinal or optic disc touch is much lower. (2) If you are not sure whether you aspirated the entire PFCL, instill a little water into the air-filled vitreous cavity (with a brief water-air exchange) and then completely remove the residual PFCL-water puddle.