Vitreous haze, vitreous pigment clumps
Wrinkling of the inner retinal surface, rolled edge of retinal break, retinal stiffness, vessel tortuosity
Full-thickness retinal folds in
Fixed retinal folds in four quadrants
Wide funnel shape
Narrow funnel shape
Closed funnel (optic nerve not visible)
The revised classification of PVR of 1991  took into account more detailed information about the location, extent, and severity of PVR in an individual eye and hence is more useful especially for clinical trials (Tables 5.2 and 5.3).
Updated proliferative vitreoretinopathy: grade classification (1991)
Vitreous haze, vitreous pigment clumps, pigment clusters on inferior retina
Wrinkling of the inner retinal surface, retinal stiffness, vessel tortuosity, rolled and irregular edge of retinal break, decreased mobility of vitreous
Posterior to equator, focal, diffuse, or circumferential full-thickness folds, subretinal strandsa
Anterior to equator, focal, diffuse, or circumferential full-thickness folds, subretinal strands, anterior displacement, condensed vitreous strandsa
Updated proliferative vitreoretinopathy: contraction type classification (1991)
Starfold posterior to vitreous base
Confluent starfolds posterior to vitreous base; optic disk may not be visible
Proliferation under the retina; annular strand near disk; linear strands; moth-eaten-appearing sheets
Contraction along posterior edge of vitreous base with central displacement of the retina; peripheral retina stretched; posterior retina in radial folds
Vitreous base pulled anteriorly by proliferative tissue; peripheral retinal trough; displacement ciliary processes may be stretched and may be covered by membrane; iris may be retracted
5.5 Surgical Management
There has been substantial improvement in the success rate of surgery for PVR progressively over the past four decades . The clinical severity of PVR is very variable, and therefore the extent and timing for surgery should be planned accordingly. In cases with the macula attached or salvageable, it is desired to perform prompt surgery. Leaving an eye with a retinal detachment and early PVR almost always will lead to further progression, so most eyes deemed to be operable should be operated on as soon as possible. On the other hand, PVR is less likely to recur if surgery is delayed until epiretinal proliferation is mature, and it may be better to wait a few days and quiet the eye down with corticosteroids if the macular vision is not salvageable until the inflammatory activity is less intense .
The objectives of vitreoretinal surgery for PVR are to release any residual retinal traction and to close any open retinal breaks. These goals may be achieved by an encircling scleral buckle, meticulous relief of all retinal traction with vitrectomy, and temporary or long-term tamponade of the retina with long-acting gas or silicone oil.
5.5.1 Circumferential Buckling and PVR
Although vitrectomy has become the main procedure for PVR, a 360° scleral buckle remains a fundamental requirement for most eyes with established PVR.
In PVR cases, the inferior part of the vitreous base becomes fibrocellular and continues to contract even after a former vitrectomy . Since it is virtually impossible to remove the whole vitreous base, placing a high encircling scleral buckle will provide support to the vitreous base against further traction. It relives peripheral anteroposterior retinal traction, closing the peripheral retinal breaks by stretching the peripheral retina over the convex buckle. Furthermore, it will relieve circumferential retinal traction by reducing the circumference of the equatorial and anterior sclera. By these two mechanisms, it will change the vector force of contraction, so the retina is no longer pulled away from the retinal pigment epithelium.
Placing a high encircling scleral buckle will help to isolate the peripheral retina from the posterior retina, forming a new, more posterior “ora serrata” on the crest of the buckle. This allows the posterior retina to remain attached in some eyes in which there is peripheral retinal detachment because of peripheral epiretinal proliferation.
Eyes with localized or relatively inactive PVR may be successfully reattached with an encircling scleral buckle, drainage of subretinal fluid, and peripheral laser photocoagulation alone. Most cases, however, require a vitrectomy and internal tamponade with silicone oil or long-acting gas.
5.5.2 Vitrectomy and PVR
Some authors rely on a meticulous vitrectomy and silicone oil tamponade without scleral buckling and report comparable results with a combined procedure , although in our experience, we prefer combining vitrectomy and scleral buckling in PVR cases. Almost all eyes with retinal detachment and PVR also require a vitrectomy to remove all vitreous gel. It is necessary to relieve all traction by division and peeling or delamination of fixed membranes causing anterior traction and to release the tractional effect on scarred shortened retina.
Vitreous can be very adherent in the vitreous base, making it difficult to shave it all and eliminate all epiretinal proliferation. These surgical steps are greatly facilitated by the advances in technology now available. Wide-angle viewing systems are either indirect and attached to the operating microscope or consist of an operating corneal contact lens. Contact lenses provide a crisper image and easier visual access to the far inferior periphery but require frequent repositioning. Indirect viewing systems provide a less panoramic view and depend on precise eye positioning, making angulation more difficult . Wide-field illumination is achieved with a range of fiber-optic light sources or a chandelier arrangement inserted into the eye through a separate pars plana entry site. Vitreous cutting probes have vastly improved, and the surgeon has the choice of smaller gauge instruments (23G, 25G) and the traditional 20G instruments. Modern vitreous probes can cycle at up to 7,500 cycles per minute and have a variable duty cycle. Shaving mode vitrectomy combines a minimum port open time (shaving mode) with a high-speed vitreous cutting (5,000–7,500 cpm) and a low vacuum (80–100 mmHg) and thus allows the instrument to be held closer to the retina.
Another major advance has been the intraoperative use of perfluorocarbon liquid (PFCL) which displaces subretinal fluid anteriorly and flattens the bullous posterior retina. This helps exposing and stabilizing the peripheral retina during dissection and demonstrates residual proliferation.
Anterior displacement from anteroposterior contraction of the vitreous base can be relieved by scissors cutting circumferentially. Anterior membranes should be eliminated. Membranes may be elevated with a vitreoretinal pick, grasped with forceps, and peeled from the retinal surface. In complex cases, bimanual dissection techniques are required, using forceps, scissors, or the vitreous probe.
In some eyes, peripheral vitreous base proliferations cannot be separated from the retina, and retinotomies or retinectomies must be considered when residual traction persists.
Immature membranes are difficult to identify and have a tendency to fragment, leaving residual cells that can reproliferate.
Internal drainage of subretinal fluid and fluid–air exchange of the vitreous compartment allow the testing of release of all retinal traction. Any persistent retinal elevation after fluid-air exchange indicates that complete release of traction has not been achieved.
Reattached retina and open retinal breaks are sealed with endolaser photocoagulation or cryotherapy. We usually prefer endolaser photocoagulation, as it induces less intraocular inflammation and associates a lower risk of hemorrhagic choroidal detachment. Intraocular tamponades in PVR cases include perfluoropropane (C3F8) gas and silicone oil (SO). Although a controlled trial showed the eventual outcomes to be similar, many surgeons prefer SO to gas because it results in less postoperative inflammation, quicker rehabilitation, and fewer reoperations .
The use of heavier-than-water SO, such as Densiron, can also improve inferior retinal tamponade in severe cases of PVR and is being increasingly used. Densiron has a specific gravity of 1.06 (higher than water) and is specially indicated in cases of RRD with inferior breaks. When injected in cases of retinal detachments with inferior retinal breaks, it displaces any aqueous (containing proliferative cytokines and activated cells) to the superior retina, where there are no retinal breaks. The Heavy Silicone Oil Study compared the effect of Densiron and conventional SO, in eyes with inferior and posterior PVR grade C or above . No significant difference between both groups was observed regarding anatomical success or visual outcomes. No significant adverse effects were observed during the course of the study, including emulsification of SO .
5.5.3 Management of the Lens in PVR
Lensectomy should be performed if the cataract is sufficiently dense to prevent an accurate visualization of the retina or in cases in which an anterior dissection of the vitreous base is needed.
The posterior capsule and the lens are eliminated with the vitreotome, using a low cut-rate and a high aspiration. Moreover, we usually polish the anterior capsule with the vitreotome using a low aspiration, in order to eliminate the remaining epithelial cells and prevent the anterior capsule opacification.
We should take into account several considerations when using SO as an internal tamponade. The lens always becomes cataractous with SO, and it can be replaced at the time of SO removal or when it becomes visually significant.
The anterior capsule should be preserved, as it provides support for future IOL implantation and compartmentalization of spaces. If the capsule is totally removed, there is risk from SO contact to the corneal endothelium in the longer term. An inferior iridotomy will reduce this risk .
If the patient is left aphakic but the anterior capsule is preserved, then it always becomes opaque in the presence of SO, and subsequent YAG laser capsulotomy is carried out at the time of insertion of an intraocular lens in the sulcus 2–3 months later .
Intraocular lens can be placed inside the capsular bag or in the sulcus in mild PVR cases. However, an IOL will provide worse anterior retinal viewing, so insertion of IOL should be avoided in anterior PVR cases.
In younger patients with a softer lens, it is possible to remove the contents and still preserve both anterior and posterior capsules. In this case, an intraocular lens is inserted after vitrectomy but before fluid–gas exchange into the bag.
5.5.4 Core Vitrectomy and Removal of the Vitreous Base
Vitreous cutting probes have vastly improved, and the three available probe sizes (20G, 23G, 25G) are all acceptable.
The 25G cutting probe is the slowest of the three sizes, although it has the smallest opening and it can be hold closer to the retina. It is more flexible, so it can be difficult to rotate the eye superiorly enough to comfortably remove vitreous off a superior retinal break with a mobile detached retina.
The 20G probe has the largest opening and most efficient fluidics, but the sclerotomies need suturing. We believe 23G is the best choice, because it is rigid enough in order to manipulate the eye while performing a peripheral vitrectomy, has similar fluidics to the 20G, and does not require suturing the sclerotomies in most cases.
Most eyes with established PVR already have a posterior vitreous detachment. Any remaining central gel should be removed completely, and then the peripheral vitreous is removed meticulously and as completely as possible, particularly inferiorly where pigment and inflammatory cells tend to gravitate. This process is facilitated by the modern, high-speed vitrectomy cutters with the port close to the tip. With these cutters, it is possible to shave the attached vitreous off the retinal surface without engaging the retina.
Modern vitrectomy cutters also offer the possibility of selecting the best parameters for each step of the surgery: core mode and shaving mode.
Shaving mode combines a high cut-rate and a low aspiration and enables us to remove the vitreous base while holding the vitrectomy port very close to the retina. Core mode combines a high aspiration and a lower cut-rate and enables us to eliminate the central vitreous very efficiently.
Removal of the inferior vitreous base is best facilitated by scleral indentation. Formed vitreous attached to the peripheral retina is also very difficult to remove if the retina is detached and mobile, and in which case it can be stabilized at this stage by partly filling the vitreous compartment with PFCL. This has the effect of stabilizing the retina by displacing the subretinal fluid anteriorly. In cases where vitreous remains attached to the retinal surface posteriorly as well as at the vitreous base, the process of removal may be facilitated by an intravitreal injection of triamcinolone. The white suspension sticks to vitreous membranes and residual vitreous gel, making them both more visible [16, 17].
5.5.5 Removal of Epiretinal Membranes and Use of Perfluorocarbon Heavy Fluid
After a meticulous vitrectomy any fixed folds or retinal contraction due to epiretinal membranes must be dealt with.
Epiretinal membranes are often poorly visible because of their transparency. Identifying these membranes becomes easier with vital dyes. Trypan blue is a dye with high affinity to tissues with high rates of cellular proliferation like ERM and stains the nuclei of damaged and dead cells, as well as the extracellular matrix. This provides better visibility and delineation of ERM during PVR surgery, enabling a more complete ERM removal and thus a higher rate of long-term reattachment [18, 19]. Membranes are peeled from the retinal surface from the posterior pole outwards. If an edge is found, it can be peeled preferably with vitreous forceps. If not, a retinal pick may help find a plane and elevate the membrane. Care must be taken to avoid creating iatrogenic retinal breaks. Special attention is given to any fixed folds where contracted membrane tends to fold the retina over underlying valleys. Any membrane involving the macula must be peeled. Some surgeons advocate the injection of vital dye such as brilliant blue at this point to stain and allow peeling of the contracted internal limiting membrane, particularly if the retinal surface at the posterior pole is still stiff. The degree of adherence of epiretinal membranes to the retinal surface varies so that some may be peeled easily in a single sheet, while many others have to be freed up in multiple pieces or delaminated. Peeling of surface retinal membranes and internal limiting membrane is much easier over attached retina. In many cases, drainage of subretinal fluid through an open retinal break or flattening the posterior retina by the injection of perfluorocarbon liquid facilitates this process.
PFCL is extremely useful in posterior PVR cases: it opens the funnel, exposing any epiretinal or subretinal membranes. PFCL stabilizes the retina during membrane peeling, acting as a second hand holding the retina in place. As areas of posterior traction are removed, PFCL is added to flatten and stabilize the peripheral retina.
Care must always be taken to avoid the risk of heavy fluid passing through a retinal break under the retina. This can occur if tractional membranes are still elevating a retinal tear. The heavy liquid fill is stopped short of any such retinal break until it is dissected, mobilized, and flattened.
5.5.6 Removal of Anterior Tractional Membranes
Fibroblastic organization of the vitreous base can cause elevation and traction of the peripheral retina. This must be sectioned to fully mobilize the retina and allow retinal reattachment. Vitrectomy should be as extensive anteriorly as possible to decrease the risk of recurrence of PVR. High-speed small-size vitreous cutters (23G or 25G) have the opening closer to the end of the probe, so they can be hold closer to the retina, facilitating the shaving of the vitreous base. Vertical action scissors are often no longer needed.
In complex cases, bimanual dissection techniques are required, using forceps, scissors, or the vitreous probe. External scleral depression and wide-angle viewing systems are extremely helpful for removing anterior tractional membranes.
In order to obtain a better visualization of the anterior membranes, we prefer to inject a PFCL bubble in the posterior pole up to the level of the membranes and then perform the staining with trypan blue.
If extensive anterior traction is noted preoperatively, then planned lens extraction can also facilitate the dissection, but with modern instrumentation and viewing systems, this option remains necessary only in very complex cases.
5.5.7 Removal of Subretinal Membranes
Subretinal membranes (SRM) may appear in up to 3% of rhegmatogenous retinal detachments. Subretinal membranes are considered a form of PVR and thus appear usually associated to epiretinal proliferation. Histopathologic studies demonstrate hypocellular membranes, with a collagen matrix and some melanic pigmentation in plaques. In previous studies the glial cells were considered to be the origin of SRM, although more recent studies identify the RPE cells as the source of these membranes . In the majority of cases, they are identified intraoperatively but do not prevent retinal reattachment.
Subretinal membranes should only be removed in cases in which they prevent retinal reattachment, as there is risk of damaging the outer retina in this procedure.
Subretinal membranes are usually associated with a worse visual prognosis, achieving BCVA ≥5/200 in 20 % of cases .
Subretinal membranes may present with different morphology. The most common configuration is single or branching brands of subretinal tissue. In some cases they may proliferate on the subretinal space conforming sheets of subretinal tissue, which are more difficult to remove without causing damage to the outer retinal layers. Other cases present with an annular peripapillary configuration that almost always prevents retinal reattachment or posterior epiretinal membrane dissection.
Annular configuration membranes should always be removed. In the rest of cases, we should test retinal reattachment intraoperatively before removing the SRM. Firstly, a complete epiretinal membrane removal should be achieved, including those extending in the anterior retina. After performing a 360° scleral indentation, we should test retinal reattachment with PFCL or air and only decide to remove SRM if residual traction persists.
Surgical removal technique for SRM
Premium Wordpress Themes by UFO Themes
Single or branching band: create a small retinotomy overlying SRM parallel to the nerve fiber layer in the superior quadrants, as far as possible from the macular area. Using a bimanual technique and a chandelier light, grasp the membrane through the retinotomy with vitreous forceps, and pull it through the retinotomy into the vitreous compartment (Fig. 5.1).
Surgical removal of subretinal membranes (SRM): single or branching band. Perform a retinotomy overlying SRM parallel to the nerve fiber layer in the superior quadrants. Using a bimanual technique, dissect the SRM with two forceps or forceps and scissors
Annular configuration producing a narrow funnel: create a peripheral 120° retinotomy, grasp SRM with forceps, and using a bimanual technique segment the membrane with scissors. Another option could be performing a superior nasal retinotomy and grasping firmly the SRM with forceps and pulling it out directly onto the vitreous cavity (Fig. 5.2a, b).
WordPress theme by UFO themes