Intricacies of the Use Of Perfluorocarbon Liquids
A review of the different types of PFO liquid exchanges.
Steve Charles, MD, FACS, FICS
Perfluorocarbon liquids are essential for giant break management; the technique is an incredible contribution of Stanley Chang, MD. Perfluoro-octane (PFO) is FDA-approved as Perfluoron from Alcon Laboratories. It is preferred over perfluorodecalin because the interface with aqueous/infusion fluid is much more visible due to a greater difference in the index of refraction.
Perfluorocarbon liquids are often used to drain subretinal fluid in lieu of simultaneous internal drainage of sub-retinal fluid and fluid-air exchange. The PFO technique is invaluable if IOL fogging occurs during fluid-air exchange. IOL fogging is more common with silicone IOLs because of higher posterior capsular opacification rates and, therefore, higher YAG rates, as well as higher thermal mass.
Fogging can occur with polymethyl methacrylate (PMMA) and acrylic IOLs as well, but at lower rates. The thermal mass is higher because the IOLs are thicker, owing to a relatively low index of refraction. If a YAG capsulotomy is present, and the anterior vitreous is intact, it should not be removed; this layer of vitreous is often sufficient to prevent IOL fogging (Figure 1).
Figure 1. An intact anterior vitreous can help prevent fogged IOL.
MANAGEMENT OF SUBFOVEAL PFO
I am surprised at how often the management of subfoveal perfluorocarbon liquid is discussed at retinal meetings. Preventing subfoveal PFO is better than accepting that it “just happens.” The key to preventing subfoveal PFO is avoiding cases with rigid retina-epiretinal membrane complexes due to severe posterior vitreo-retinopathy or diabetic tractional retinal detachment, as well as the combination of macular hole or posterior breaks and rigid retina-ERM complexes.
Perfluorocarbon liquids are often used for retinal stabilization during ERM peeling for PVR management. Although this technique reduces retina movement, I rarely find it necessary, as it is a significant factor in the causation of subfoveal perfluorocarbon liquids.
In addition, an optimal injection technique is crucial for avoiding multiple small bubbles, which are more likely to migrate under the retina. Very small subfoveal PFO bubbles can be observed with good vision. If removal is required, most surgeons insert a 39-gauge cannula (referred to as 41-gauge by some) into the subfoveal space via a temporal, perimacular, punch-through retinotomy.
This method can damage the retinal pigment epithelium and cause a choroidal neovascular membrane, as well as damage the photoreceptors. Some surgeons start by creating a posterior retinal detachment using a 39-gauge cannula and a technique similar to macular translocation, the fortunately obsolete operation. This method shears off photoreceptor outer segments and RPE apical processes.
I have never had a case with subfoveal PFO but have managed a few cases operated on by others. I have had excellent success by making a very small retinal slit at the top of the bubble using a 25-gauge MVR blade. The bubble can be easily displaced from the subretinal space and the slit massaged closed with a soft-tip cannula. Fluid-gas exchange or possibly fluid-air exchange is then used just as in macular hole cases.
TYPES OF PFO LIQUID EXCHANGES PFO Exchange
The MedOne 25-g dual-bore, cannula connected to an Alcon VFC with an 8-to-10-psi (~55 to 69 kPa) pressure setting (80 psi [~551 kPa] is utilized for silicone oil) is ideal for precise PFO injections (Figure 2). It is unsafe to place a needle connected to a manually operated syringe in the eye and attempt to manipulate the plunger with the syringe-holding hand or to have an assistant perform this task.
Figure 2. A 25-g cannula connected to a VFC is ideal for PFO injections.
The flexible tip of the dual-bore cannula should be positioned near the optic nerve head before initiating the injection. Direct visualization is essential because the PFO injection must start at the lowest point of the retinal surface to avoid creating multiple bubbles.
The MedOne dual-bore cannula must be moved anteriorly while injecting at the top of the bubble as it enlarges, to prevent the formation of multiple bubbles as well as the loss of PFO through the proximal fluid egress port. Valved cannulas are ideal to prevent the loss of PFO, as well as bubbling, as instruments are exchanged.
Perfluoro-octane–gas exchange is the inverse of the injection process; use a soft-tip cannula to remove the PFO and not from the optic nerve head. Maintain the cannula tip near the junction of peripheral retina at the top of the PFO bubble to remove all aqueous, subretinal fluid and residual infusion fluid before removing any PFO.
This technique is essential for reducing the likelihood of subretinal fluid re-accumulation, as well posterior movement of the flap, in giant break cases.
Sequential PFO-Air-Oil Exchange
Posterior migration of the flap in giant break cases during PFO-air exchange is due to the removal of PFO before all of the aqueous fluid is removed. Extreme care must be taken to keep the soft-tip cannula near the junction of the peripheral retina and the top of the PFO bubble to remove aqueous, subretinal fluid and residual infusion fluid.
Direct PFO-Oil Exchange
A chandelier is required during direct PFO-oil exchange because the short, thin-walled silicone oil injection cannula connected to the VFC (80 psi) is held in one hand, and the soft-tip cannula for PFO removal is held in the other, so there is no hand to hold the endoilluminator. Use of the chandelier enables excellent visualization and precise positioning of the soft-tip cannula at the optic nerve head for PFO removal.
I rarely use chandeliers because they require a fourth wound and decrease the ability to see the vitreous and internal limiting membrane, as they cannot provide focal, specular, or retroillumination.
It is now well known that wound construction is a crucial issue in sutureless surgery. Conjunctival displacement, a 300-µm scleral tunnel, and removing vitreous from the sclerotomy are crucial for preventing vitreous wicks and hypotony.
Many surgeons fail to use these essential techniques when using chandeliers. Fortunately, the Alcon chandelier system is designed to work with conventional cannulas and therefore supports correct wound construction.
I have used medium-term PFO off-label since it became available to repair selected inferior retinal detachments and giant retinal breaks. The technique allows the patient to stand, sit, travel by airplane, and even work and drive provided the other eye has good vision.
The technique involves removing all peripheral vitreoretinal traction, followed by attaching the retina with PFO, and finally endophotocoagulation surrounding all retinal breaks and suspicious areas. A total PFO fill is utilized and infusion-clamped after total PFO fill. The PFO is left in place for two weeks, until the laser marks pigment, and then is removed with a 25-g system.
Topical difluprednate is used to reduce the foreign-body inflammatory response. Intravitreal triamcinolone was used before difluprednate became available; this method occasionally results in triamcinolone acetonide deposits on the lens or IOL.
Perfluorocarbon liquids are essential for giant break management, ideal for IOL fogging scenarios, and occasionally useful in PVR cases. The injection and exchange techniques described here, in addition to avoiding use in “stiff retina” cases, reduce the chances of subfoveal PFO. It is better to prevent, rather than treat, this problem.
Careful attention to the details of exchange methods reduces the chances of giant break slippage, although medium-term PFO should be considered for inferior, temporal, and nasal giant break cases, as well as all types of inferior detachments. RP
|Steve Charles, MD, FACS, FICS, is clinical professor of ophthalmology at the University of Tennessee College of Medicine in Memphis. Dr. Charles reports significant financial interest in Alcon. He can be reached via e-mail at email@example.com.|