(1)
St. Johns, FL, USA
(2)
Helen Keller Foundation for Research and Education, International Society of Ocular Trauma, Birmingham, AL, USA
(3)
Consultant and Vitreoretinal Surgeon, Milos Eye Hospital, Belgrade, Serbia
(4)
Consultant and Vitreoretinal Surgeon, Zagórskiego Eye Hospital, Cracow, Poland
As the VR surgeon removes gel from the vitreous cavity, he typically replenishes it with BSS. Gaseous materials or fluids, in addition to being used as intraoperative tools, may be employed as “tamponade,” kept postoperatively for weeks or months or permanently.1 During the operation, several exchanges between these materials may need to be performed.
35.1 Air
Air in the VR surgeon’s hands has many uses (see Sect. 14.1), of which retinal reattachment (F-A-X, see Sect. 31.1) is the most important. Air, which does not expand after implantation,2 is rarely used3 as a postoperative tamponade since it disappears from the vitreous cavity within days.
Pearl
The air should never be injected at high pressure to avoid retinal damage by the jet stream, and it must be filtered first (Millipore 0.22 μ, EMD Millipore, Billerica, MA, USA).
35.2 Gases
35.2.1 General Considerations
Depending on the type and concentration of the gas, it may stay in the vitreous cavity for ~2 weeks (SF6) or ~2 months (C3F8). As N2 and O2 diffuse into them, pure gases expand after their implantation, most rapidly within the first 8 h; SF6 needs ~2 days to reach its maximum expansion, C3F8 needs ~4 days. For this reason, no more than 1 ml of pure gas should be injected into an emmetropic eye.
The potential for gas expansion during general anesthesia as the N2O diffuses into the intravitreal gas4 and the “collapse” of the intravitreal gas upon termination of the general anesthesia are important issues requiring proper adjustment from both the surgeon and the anesthesiologist (see Sect. 14.2).
The beneficial effects of the gas include their surface tension, buoyancy, space occupation, and the fact that proliferating cells do not penetrate it, nor will they attach to its surface.
35.2.2 Surgical Technique5
Typically, surgeons flush the air-filled eye with a premixed concentration of the gas. This method works but wastes a lot of gas. My technique is the following, regardless of the type of gas used:6
Prepare two 2 ml syringes. Leave one empty for air withdrawal and fill the other with 2 ml of pure (undiluted) SF6. Loosely attach a short 27 g needle to the empty syringe.
Remove all cannulas.
Through a superotemporal location, insert the needle attached to the empty syringe into the vitreous cavity. Aim toward the center of the eye and constantly monitor the needle,7 keeping it in the same position throughout.
Press the cone of the needle against the orbital bone or secure it firmly with your fingers, or both.8
Withdraw ~1.5 ml of air9 into the syringe. The nurse must announce the amount of air being removed at every 0.5 ml interval.
Detach the syringe from the needle, and hand it to the nurse. Attach the gas-filled syringe to the needle’s cone.
Inject ~1.5 ml of the gas as the nurse announces the progress. With your nonworking hand’s index finger tap on the eye to make sure the IOP is in the normal range.
Pearl
If a gaseous tamponade is used, the patient must be warned, both pre- and postoperatively, that it is normal to initially “see dark” through the bubble, but it is not normal to have severe pain. If there is significant pain, he must seek help immediately. Vision will improve soon, even while the gas bubble is still in the eye, although the interface may remain bothersome, especially when the gas-aqueous interface is right in front of the macula.
35.2.3 Gas Injection into the Nonvitrectomized Eye
35.2.4 The Eye with Gaseous Tamponade
Even if the implanted gas is of a nonexpansile concentration, the gas (air) will expand if the atmospheric pressure drops. Patients with air/gas in their vitreous cavity should not fly or be exposed to an increase in elevation exceeding a few hundred meters.11 The acute rise of the IOP, should these warnings be neglected, can lead to blindness.
Q&A
Q
What if a patient needs a gas tamponade but must travel by airplane, lives on a mountain, or has to travel through a mountain?
A
Silicone oil must be used, not gas – and this needs to determined preoperatively.
35.3 PFCL12
35.3.1 Indications to Use Heavier-Than-Water Liquids
Flipping the inverted flap of a giant retinal tear.
Keeping a highly mobile detached retina (relatively) immobile in RD surgery.
Temporarily reattaching the macula to allow ILM peeling (see Sect. 32.1.6).
Keeping an-already-opened funnel open in PVR surgery (see Sect. 32.3.1.5).
Floating (lifting) dislocated lens particles or IOL or IOFBs toward the iris.
Facilitating the removal of liquefied blood in eyes with suprachoroidal hemorrhage (see Sect. 60.2).
Pushing residual subretinal fluid toward the retinotomy (see Sect. 31.1.2).
Displacing submacular blood (see Sect. 36.4).
35.3.2 Surgical Technique
35.3.2.1 Implantation
All tractions must be addressed before PFCL injection; otherwise, only small amounts to stabilize the retina may be used, and only if no posterior retinal break is present (see below).
If possible, avoid injecting into an air-filled eye since the PFCL will rapidly start to evaporate and collect on the back surface of the IOL/posterior capsule (see Sects. 14.4 and 31.2). The evaporation is so fast that the PFCL disappears even from the bore of the needle13 and explains the introduction of a small air bubble every time PFCL is injected; multiple injections result in multiple air bubbles (see Fig. 33.1).
Never inject the PFCL too fast. The BSS must drain to avoid a circulation-stopping IOP elevation (see below).
If the injection is not continuous, several large bubbles may form, but they will rapidly coalesce.
If small amounts are injected and many small bubbles form,14 shake the eye and they will coalesce. To prevent the fish-egging, keep the flute needle’s tip inside the enlarging PFCL bubble.
Never try to fill the vitreous cavity with PFCL if there is a posterior retinal break under traction.15 The bubble will escape into the subretinal space instead of flattening the retina. It is the traction, not the presence of the break, why PFCL is contraindicated.16
If the PFCL is injected in order to be exchanged for silicone oil, it is best to fill the vitreous cavity completely. This avoids creating a “fluid sandwich,”17 in which case the completion of the drainage is lengthier and technically more complex (see below, Sect. 35.5).
When injecting into an eye that has a foreign object18 in the vitreous cavity, avoid pouring the PFCL on top of, rather than around and underneath, the object.
35.3.2.2 Removal19
The PFCL bubble has very low resistance to flow and readily escapes the eye,20 regardless of what replaces it. PFCL is also easy to discern, irrespective of what it is interfacing with. It is used almost exclusively as an intraoperative tool, although occasionally left behind21 for a few weeks.
The larger the bubble, the flatter its anterior contour; a smaller bubble will form a sphere.
During the initial phase of the removal the apparent spread (horizontal dimension) of the bubble is unchanged, only its height22 seems to decrease.
Obviously, the deepest point of the eye is where the bubble will be easiest to collect. However, the eye is often rotated during removal and the single large PFCL bubble may break up into smaller ones, which lose connection with each other; these must then be aspirated separately.
Residual PFCL bubble in the vitreous cavity: not a per se indication for removal.
Residual PFCL bubble subretinally: not a per se indication for removal.
If it is subfoveal, though, it should be removed as it may be toxic. A small retinotomy is sufficient, and the bubble will readily escape.
Residual PFCL bubble in the AC: easy to recognize since in a patient sitting at the slit lamp the bubble will be inferior. A small inferotemporal paracentesis will result in spontaneous drainage (see below, Sect. 35.6).
35.4 Silicone Oil
Silicone oil is used as a temporary or permanent substitute. Its major drawback is that in the former case the patient must undergo a second operation to remove the oil. “Oil changes” are also needed if the longevity of the oil23 is shorter than its required duration. The choice between silicone oil and gas tamponade in RD surgery is discussed under Sect. 54.5.2.5.
35.4.1 Selecting the Type of Silicone Oil to Implant
Silicone oil is available in “normal” viscosity (1,000–1,300 cst) and high viscosity (5,000 cst; see Sect. 14.3.1). The more viscous the oil, the less likely it is assumed to emulsify.24 The normal oil provides better tamponade superiorly, the heavier-than-water version inferiorly.
I use almost exclusively normal oil (lighter than water and low viscosity).
The only exception is eyes that require a permanent fill (see below), in which case I use 5,000 cst oil.
I do not use heavy oil.
While heavy silicone oils can indeed prevent inferior proliferations, they increase the risk superiorly, where they are technically more difficult to access and deal with.
Q&A
Q
Long–acting gas or silicone oil?
A
For me this is a rather easy question to answer. If an eye requires long-term (months) tamponade, I prefer oil (see Table 35.1).
Table 35.1
Comparison between long-acting gas and silicone oil
Variable | Long-acting gas | Silicone oil |
|---|---|---|
Concurrent IOL implantation | May require visco in the AC; power calculation is for gas-free condition | May require visco in the AC; power calculation is for oil-free condition. Adjustment is needed if the oil is to be retained forever |
Injection of medication into tamponade | No if the fill is 100% | Yes; the dose may have to be reduced |
Need for positioning | Yes | No, except in certain circumstances and even then only initially (see the text for more details) |
View of retina after the implantation | Poor, then improves | Excellent from day 1 |
Risk of IOP elevation | High initially then none | Normal initially then may increase (emulsification) |
Duration of tamponade | Several weeks | Months to forever |
Effect on PVR prophylaxis | No; if PVR develops, it usually but not necessarily starts inferiorly | Possibly; if PVR develops, it starts inferiorly |
Possibility of sudden collapse of retina (closed funnel) | As long as gas is present: no | As long as silicone oil is present: no |
Subretinal migration of tamponade | Very small risk, at the time of implantation (see Fig. 54.9b) | No until PVR develops; with ongoing PVR, the risk increases |
Phthisis risk | Unchanged | Reduced if the fill is 100% (see the text for more details) |
Issues with altitude (lower atmospheric pressure) | Yes; avoid as long as gas is in the eye | No |
Another surgery needed to remove tamponade | No | Yes |
35.4.2 General Considerations
A silicone oil fill is supposed to 100% (see below and Sect. 14.3.2).
A less-than-complete fill increases the risk of emulsification and the likelihood that the cells responsible for proliferation will aggregate inferiorly (hence the rationale to use heavy oil).
Unless the oil is to be kept permanently (see below), the patient must understand that oil implantation involves at least one additional operation.
The patient has to accept that the eye’s refraction will be significantly changed by the oil’s presence.
If there is a risk of oil prolapse into the AC, the patient may have to position (facedown) in the first few days.25
35.4.3 Indications
35.4.3.1 Semipermanent Tamponade
Prevention of rebleeding, mostly in eyes with PDR (see below and Sect. 52.2).Maintaining retinal (re)attachment.
Prevention of PVR development in eyes at high risk.
Prevention of the development of a closed funnel in RD/PVR/PDR.
Prevention of reproliferation in PVR (including giant tear) and PDR.
Macular hole.27
35.4.3.2 Permanent Tamponade
Hypotony28 or phthisis.
Repeatedly recurring PVR, which leads to RD if the oil is removed.
While the oil cannot be removed, an inferior RD can be left to persist29 under the oil as long as the detachment does not involve/threaten the macula.
Recurrent VH. Most often seen in diabetic patients; they may have a full panretinal laser treatment, no visible proliferation, and good systemic control of the diabetes and blood pressure, yet the intravitreal bleeding keeps recurring unless a silicone oil tamponade is present.
35.4.4 Implantation
If an IOL is present, perform a large posterior capsulectomy.
Posterior capsular opacification is inevitable.
Hydrophobic IOLs (e.g., silicone) should be removed since the oil sticks to them.
It is much faster and technically easier to implant the oil under air than BSS (see below, Sect. 35.5).
To achieve a truly 100% fill, make sure you remove all the vitreous, suprachoroidal, and subretinal fluid/blood and do not overinflate the AC with visco.30The fastest way is to suture-close the infusion sclerotomy and inject the oil superonasally, directly through a short needle attached to the syringe, while draining the air through the superotemporal sclerotomy with the flute needle.
The easiest way to implant is to attach the syringe containing the oil to the tubing of the infusion cannula at the stopcock; this way the tubing is short.
Use the vitrectomy machine’s “viscous fluid injection” mode (or ask the nurse to do it31).
Do not apply too high an injection pressure – the tubing can disconnect at either end and the oil will be lost. You can gradually increase the pressure if all goes well.
While you are pressing the pedal and inject the oil, have the nurse monitor the syringe and the tubing to make sure that nothing gets disconnected.
Simultaneously aspirate the PFCL (BSS) with the flute needle held in the dominant hand. Aspiration in these cases is from the bottom of the eye.
If the eye is filled with air (the recommended option), aspirate it from the anterior part of the vitreous cavity, through the temporal sclerotomy.
There is no initial need to aspirate the air; it is compressible plus almost always leaks spontaneously through the cannula, even if it is valved. Use the time during this initial phase of oil implantation to suture the nasal sclerotomy (see below).
Pearl
Suturing the sclera is a rare chance for the VR surgeon to experience tactile feedback. Even if the needle is invisible underneath a swollen conjunctiva, the surgeon will feel the sclera’s extra resistance against the needle’s advancement. However, if the eye is soft, this feedback disappears, and the only way the surgeon can determine whether the needle indeed engaged the sclera is to try to lift the tip of the needle. If he caught only conjunctiva, the needle will easily lift it; if the sclera has also been penetrated, the needle’s tip cannot be lifted.
Suture the superotemporal sclerotomy before you complete the oil injection.
Inject silicone oil to achieve an IOP that is slightly higher than normal (~30 mmHg).
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