Ординатура / Офтальмология / Английские материалы / Retinal and Vitreoretinal Diseases and Surgery_Boyd, Cortez, Sabates_2010

•Suprachoroidal Hemorrhage

•Management of Retinal Detachment Following Keratoprosthesis

•Surgical Management of Retinopathy of Prematurity

•Surgical Removal of Submacular Hemorrhage in Conjunction With TPA

•Improving Visualization in Cases of Diabetic Retinal Detachment

•Endophthalmitis

•Retinal Incarceration

•Control of Bleeding During Pars Plana Vitrectomy

•Removal of Intraocular Foreign Bodies

•Treatment of Rhegmatogenous Retinal Detachment

•Retinopathy of Prematurity

Giant Retinal Tear

Prior to the advent of perfluorocarbon liquidsinthemanagementofgiantretinaltears, texts on the subject by experienced surgeons often described the preoperative preparation of the patient with regard to postoperative positioning and body rolling. Certainly this has changed with the advances in the use of perfluorocarbon liquids and silicone oils during complicated vitreoretinal surgeries.

Scleral buckling alone can be considered in giant retinal tears with posterior flaps that are not inverted and in giant breaks, such as retinal dialysis. The use of perfluorocarbon liquids however should be considered essential for giant retinal tears in which the posterior margin of the tear has inverted and must be manipulated during vitrectomy (Figure 6 and 7). Giant tears complicated

by moderate or severe degrees of proliferative vitreoretinopathy are also best managed with the perfluorocarbon liquids. Traumatic giant tears associated with vitreous or retinal incarceration, or those with severe vitreous or subretinal hemorrhage may also be considered as preferred indications for perfluorocarbon use.

Scleral buckling is not required in eyes with mobile posterior flaps that show no sign of PVR, since there is no vitreous traction on the posterior flap of the tear. An encircling scleral buckle may actually be disadvantageous in these eyes because a decrease in the circumference of the globe resulting from the pressure of the buckle may allow the development of radial folds as the retina flattens. In some cases, the scleral buckle also becomes an insulating barrier that prevents adequate application of additional cryotherapy treatments if they are needed later.

Ultrasonic fragmentation of the clear lens is done if it is subluxated. Many eyes with giant retinal tears are larger in axial length and frequently highly myopic. In these eyes the ora serrata is located more posteriorly, allowing the use of a vitreous cutter to excise the cortical vitreous gel close to the vitreous base, without injuring the lens.

When the pars plana is narrow, or in eyes with a small pupillary opening, it may be advantageous to remove lens so that the peripheral vitrectomy can be more complete, or to visualize the edge of the tear better. Delaying lensectomy until the perfluorocarbon liquid has unfolded the posterior retinal flap may be helpful by preventing any lens

fragments from migrating into the subretinal space.

After the central vitrectomy has been completed and the tear is gently unfolded any posterior epiretinal membranes are removed and pigment clumps on the retina are aspirated using a flute needle with a silicone tip. A small amount of perfluorocarbon liquid (0.5 to 0.8 ml) is injected over the optic disc and macula. The flattening effect is observed, and the retina is examined for preretinal or subretinal membranes, as well as for the position of the macula. A finding of ectopia indicates traction that has displaced the macula in a direction in which membranes have contracted and shortened the retina. Any peripheral membranes should be removed before additional perfluorocarbon liquid is injected. All membrane dissection and peeling should be done ahead of the meniscus of the perfluorocarbon liquid bubble. When subretinal membranes are seen, the perfluorocarbon liquid is aspirated and the membranes are grasped after inverting the retinal flap.

The margin of the tear can be treated with either cryotherapy or laser photocoagulation. In most instances, endophotocoagulation is preferred, but when the margin of the tear is too peripheral, cryotherapy or laser photocoagulation using an indirect ophthalmoscopic delivery is used. Both treatments can be applied through the perfluorocarbon liquid, and one row of cryotherapy or two rows of continuous laser are usually sufficient (Figure 7). Since the retina is flattened by

the perfluorocarbon liquid during treatment, there is minimal dispersion of retinal pigment epithelialcells,andtheclumpingofsubmacular pigment epithelial cells sometimes seen after extensive cryotherapy is prevented.

The extended, long-term tamponade agent should now be selected. Perfluorocarbon liquids can be directly exchanged with either gas or silicone oil. In general, giant retinal tears of 180 degrees or less can usually be managed with a gas tamponade, while breaks larger than 270 degrees are probably best managed with silicone oil. When a gas tamponade is chosen, an automated air infusion system should also be used during the air-fluid exchange. A flute or extrusion needle with a soft silicone tip is placed near the margin of the tear. Perform a slow and deliberate fluid-air exchange, stopping frequently to allow the edges of the torn retina to dry as much as possible.

As the air bubble descends, it flattens the anterior retina, expressing the subretinal fluid through the break. All saline at the edge of the break should be carefully removed before proceeding to aspirate the perfluorocarbon liquid posteriorly. This maneuver reduces the chance of slippage of the posterior flap, since any remaining subretinal fluid will tend to flow posteriorly, causing the posterior retinal flap to also slide posteriorly. If a small amount of slippage is encountered, the situation can be managed by injecting a small amount (1.0 to 1.5ml) of balanced salt solution into the vitreous cavity at the end of the operation. The vitreous cavity is then

flushed with 20 ml of a mildly expansile mixture of perfluoropropane gas and air. The patient’s head is appropriately rotated into the prone position after the completion of surgery to correct the slippage. Infrequently, the intrinsic elasticity of the detached retina results in extensive slipping and folding under air. When this occurs, the air should be replaced by balanced salt solution, and perfluorocarbon liquid re-injected to reposition the retinal detachment. When the tear is successfully repositioned, direct exchange of the perfluorocarbon liquid for silicone oil will prevent slippage and folding of the retina. As the silicone oil fills the eye, its descending meniscus engages the edge of the tear and prevents slippage because silicone oil is relatively incompressible compared to air.

When silicone oil is selected for extended tamponade, the perfluorocarbon liquid

is directly aspirated as the silicone oil is injected with an automated infusion pump (Figure 8). When the silicone oil is first injected, the soft-tipped flute or extrusion needle is placed anteriorly near the edge of the tear to aspirate all of the saline anterior to the perfluorocarbon. When the silicone bubble contacts the perfluorocarbon liquid, the interface is visible and the perfluorocarbon is then aspirated from an anterior to posterior direction. Due to the much lower viscosity of perfluorocarbon liquid, it is much more easily aspirated than the silicone oil. After the main bubble of perfluorocarbon liquid is removed, small bubbles of perfluorocarbon may be difficult to distinguish from air bubbles that have mixed with the silicone oil during injection.

However, within seconds, the air bubbles will float anteriorly in the silicone oil, while

the small droplets of perfluorocarbon liquid will descend onto the surface of the retina where they can be easily aspirated.

Risks

The clinical trials of perfluorocarbon liquids have demonstrated two risks associated with the use of these materials; subretinal migration and residual droplets of the perfluorocarbon liquid postoperatively. Both these events have been reported in cases involving giant retinal tear.

When small bubbles are noted to have slipped subretinally, they can usually be aspirated using a flexible tip extrusion cannula that is passed subretinally through the same break that the perfluorocarbon liquid migrated through, or by stroking anteriorly in a brushing motion with the flexible tip of the cannula in a gentle motion across the retinal surface. Small bubbles that typically lodge in the vitreous base can typically be aspirated with no complications at the time of surgery. Neither subretinal or residual mobile droplets of perfluorocarbon liquids have been associated with any adverse clinical event, however, if the situation warrants subsequent surgical intervention may be necessary to remove them.

Proliferative Vitreoretinopathy (PVR)

As with giant retinal tear, perfluorocarbon liquids are a useful tool for the hydrokinetic manipulation of the retina during vitreous surgery for moderate to severe forms of proliferative vitreoretinopathy. The physical and chemical properties of perfluorocarbon liquids lend themselves well to such intraoperative challenges as opening a funnel detachment, providing counterpressure to facilitate the removal of preretinal membranes, and displaying areas of residual traction.

Surgery is performed by means of a 20, 23 or 25 gauge, three-port, pars plana approach. In phakic eyes, a lensectomy is usually performed. A broad encircling scleral buckle supporting the region of the vitreous base may be added if not already present from previous surgery.

When adherent membranes cannot be removed, a circumferential relaxing retinotomy may be performed anterior to the level of the perfluorocarbon liquid. The stabilizing effect of the perfluorocarbon liquid assists in this maneuver. The flattening effect of the perfluorocarbon liquid, and the subsequent anterior displacement of subretinal fluids often eliminates the need to perform a posterior

drainage retinotomy, as subretinal fluids are forced upward and out the anterior retinal breaks or tear (Figure 9). By reducing the need for posterior retinotomy to facilitate internal drainage of subretinal fluid, potential complications such as bleeding and the reproliferation that often occurs at the retinotomy site is reduced. If traction from subretinal membranes is present, it may be necessary to create a posterior retinotomy sufficient to facilitate their removal. This is done after the removal of a volume of perfluorocarbon liquid sufficient to bring the fill level posterior to any such area of traction.

After all areas of traction have been removed and the posterior retina has been flattened by the perfluorocarbon liquid, a partial fluid-air exchange with internal drainage of subretinal fluid flattens the anterior retina and breaks against the buckle. Laser photocoagulation can be applied through the perfluorocarbon liquid, and laser treatment should be applied for the full 360 degrees over the scleral buckle, and to the areas surrounding all retinal breaks. The air bubble replaces the infusion fluid above the perfluorocarbon liquid, and keeps the posterior retina in place. After completion of

laser, the remaining perfluorocarbon liquid is removed with a 20 gauge flute or soft tip cannula, and the air filled vitreous cavity is replaced with either an air-perfluoropropane gas mixture or silicone oil as the long-term vitreous replacement.

Clinical experience with perfluorocarbon liquids has demonstrated that potential complications related to their use are minimal. Subretinal migration and postoperative residual perfluorocarbon droplets appear to be the only two noted. Subretinal migration can usually be handled in PVR cases by aspirating the material through the same retinal break in which it originally migrated. Small residual droplets are a more common problem postoperatively, perhaps due in part to their ability to be concealed in the peripheral fundus. No postoperative complications have been observed after long-term follow-up for up to two years in the case of the Perfluoron clinical trial. They are best avoided by carefully avoiding dispersion of the perfluorocarbon liquid at the time it is injected. Perfluorocarbon liquids are not tolerated in the anterior chamber, with larger bubbles causing corneal edema within 2-3 days at the site of contact.

Trauma

Blunt or penetrating ocular trauma elicits a broad range of responses, including intraocular bleeding, severe inflammation, fibrous proliferation, and/or cyclitic membrane formation. Retinal detachment may result from any one or a combination of these, or from the injury itself. Further, there is the concept

of “surgical trauma” in instances such as relaxing retinotomies in retinal detachments complicated by proliferative vitreoretinopathy, traumatic detachment or proliferative diabetic retinopathy.

Perfluorocarbon liquids are a useful intraoperative tool during vitreous surgery in the management of complications arising from severe ocular trauma (Figure 10). The indications for perfluorocarbon liquids in penetrating trauma are: vitreous hemorrhage and retinal detachment, expression of liquefied subretinal blood, traumatic proliferative vitreoretinopathy, traumatic giant retinal tears or dialyses, retinal incarceration, and selected intraocular foreign bodies. In cases of traumatic vitreous hemorrhage with retinal detachment, the retina can be flattened and immobilized while opacified hemorrhagic vitreous can be cut and aspirated more safely. Liquefied blood can often be expressed from thesubretinalspacewithoutmakingaposterior drainage retinotomy, improving the potential for macular function. In cases of retinal incarceration, perfluorocarbon liquids can be used to open the folds and free epiretinal membranes, within the incarcerated retina. If incarceration is located peripherally, a relaxing retinotomy may be required to free the retina from the injury site.

Often, visualization is an extremely difficult challenge in trauma cases due to excessive intraocular bleeding21. Perfluorocarbon liquids can provide improved visibility due to their immiscibility with blood or ocular fluids. Their high specific gravity also may provide some improved control due to the tamponade force of the material.

Long-term retinal tamponade may be obtained by any one of three techniques: perfluorocarbon liquid/air exchange, followed by air-gas exchange; perfluorocarbon liquid/air exchange followed by the injection of silicone oil into the air-filled eye; or direct perfluorocarbon/silicone oil exchange. The first technique is performed in cases receiving a long-term gas tamponade, and the second and third are associated with the use of silicone oil as the long-term vitreous replacement. In all techniques, intraocular irrigation fluid anterior to the perfluorocarbon liquid interface is first removed by aspiration during the initial injection of air or silicone oil. Subsequently, aspirate perfluorocarbon liquid and any residual subretinal fluid at the

anterior-most edge of the retinotomy, working posteriorly along the edge of the retinotomy as the perfluorocarbon meniscus recedes, and allowing adequate time for the edge of the retinotomy to dry as much as possible. This approach allows complete removal of fluid at the retinotomy edge, and helps prevent posterior retinal slippage.

Dislocated Lenses

The popularity of phacoemulisification in cataract and intraocular lens surgery has lead to a relative incidence of dislocated crystalline lenses or lens fragments, and subluxated intraocular lenses.

The specific gravity of perfluorocarbon liquids is greater than that of crystalline lenses, polymethylmethacrylate (IOL’s), silicone or acrylic intraocular lenses, and allows the surgeon to gently float the dislocated lens or fragment off the retina following a “complete” vitrectomy, by injection of the perfluorocarbon liquid under the object, and by using the previously described techniques for maintaining a single large perfluorocarbon bubble (Figure 11). Once elevated, the lens can be removed via the limbus using a vectus or IOL forceps). Fragmentation of nuclear particles can be performed in midvitreous on a cushion of perfluorocarbon liquid, since the perfluorocarbon liquid will

act as a “shock absorber” for the ultrasonic energy. However, it should be noted that the perfluorocarbon liquid bubble tends to have a convex surface, and small particles may tend to gravitate toward the periphery where they become more difficult to detect and manage unless the surgeon has the advantage of a “wide angle” viewing system.

In situations where a posterior chamber IOL requires fixation by suturing, the IOL can be held in position behind the iris plane by the perfluorocarbon liquid, thus helping to avoid the need for the use of forceps or snares.

Where retinal detachment and a dislocated lens both exist, perfluorocarbon liquids simultaneously combine lens flotation with subretinal fluid displacement via anterior breaks, often avoiding the need for a posterior retinotomy.

It must be stressed that a complete vitrectomy is required, including generous clearance of basal vitreous before the infusion of perfluorocarbon liquids in any eye. In the presence of an incomplete vitrectomy, the lens or fragment will often become entrapped in basal gel, and significant residual amounts of the perfluorocarbon liquid may be trapped and retained in the basal vitreous. Following vitrectomy, a careful fundus examination should be done either intraoperatively or postoperatively to rule out retinal breaks.

Conclusion

The clarity of perfluorocarbon liquids, with a refractive index close to that of water, allows the use of a conventional contact lens for vitreous surgery while the low viscosity facilitates tissue manipulation, injection, and removal. Perflurocarbon liquids represent the only class of heavier-than-water vitreous substitutes, but current agents cannot safely remain in the eye for an extended time. Research efforts are therefore focusing on longterm tamponading vitreous substitutes that can support the inferior retina. This would reduce the need for prolonged postsurgical face-down positioning and may increase the anatomic success rate in management of PVR by displacing proliferative cells from the inferior quadrants of the retina.

References

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