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CONTROVERSIES IN CARE: Shaving the Vitreous Base in Vitrectomy for RRD

What makes for the perfect shave?

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Pars plana vitrectomy (PPV) without scleral buckle surgery (SB) is the most popular treatment of uncomplicated primary rhegmatogenous retinal detachment (RRD; Figure), and its use is increasing.1 Likely contributing factors favoring PPV as the preferred surgical treatment over SB or a combined PPV/SB surgical approach include advances in small-gauge vitrectomy surgery; improved wide-angle viewing systems; avoidance of complications typically associated with scleral buckles, such as postoperative strabismus, anterior-segment ischemia, and increased myopic refraction; and reduced experience with SB during fellowship training. Single operation success rates with PPV for RRD are very high and were recently noted to range from 91% to 96%.2

Figure. Rhegmatogenous retinal detachment, right eye, with vitreous hemorrhage. Note the retinal tears in the superotemporal vitreous base region, associated with peripheral retinal lattice degeneration.

The greatest threat to RRD surgical success is proliferative vitreoretinopathy (PVR). Proliferative vitreoretinopathy, which occurs in 5% to 10% of all RRD cases (usually within the first 2 months), consists of formation of contractile avascular intravitreal, preretinal, or subretinal membranes. It is responsible for approximately 75% of all postoperative redetachments.3,4 Proliferative vitreoretinopathy results from abnormal cellular proliferation of dedifferentiated astrocytes and retinal pigment epithelial cells, which form these contractile, fibroblast-like cells in sheets/membranes at the vitreoretinal interface.4,5 These membranes are associated with type I collagen, in contrast to the usual type II collagen seen in normal vitreous.6

Whether PVR occurs more frequently in vitrectomized eyes compared to nonvitrectomized eyes (for instance, with SB only) has often been pondered. One study showed that, following intraocular injection of tissue-cultured fibroblasts, vitrectomized rabbit eyes developed more PVR than nonvitrectomized eyes.7 Theories as to why this may occur include an antiproliferative cytokine milieu in the vitreous (predisposing to PVR after vitrectomy), or the physical separation afforded by the vitreous collagen between the retina and the PVR-stimulating cytokine rich environment; once vitrectomy has occurred, this protection is lost.

The remaining vitreous skirt in vitrectomized eyes has been suspected to be a scaffold for PVR, predisposing the eye to surgical failure. Scleral-depressed vitreous base “shaving” has long been advocated to reduce PVR and associated postoperative anterior and circumferential traction and improve single operation success rates in RRD.

In phakic patients, access to the vitreous base is more difficult without iatrogenic trauma to the lens, making shaving of the vitreous base challenging, perhaps predisposing to redetachment from PVR. Recently, however, a retrospective, consecutive case series demonstrated excellent RRD surgical results using PPV without scleral-depressed vitreous base shaving, contradicting traditional thought.8 Have smaller gauges and better viewing systems negated the need for scleral depression during vitrectomy? We are fortunate to have commentary on this important subject by Justis Ehlers, MD, from the Cole Eye Institute in Cleveland, Ohio.

Vitreous Shaving in Primary Management of Rhegmatogenous Retinal Detachment

Justis P. Ehlers, MD

Primary pars plana vitrectomy has become the most common approach to RRD repair. We are lucky to have numerous approaches to retinal detachment repair, including SB, combined buckle/vitrectomy, primary vitrectomy, and pneumatic retinopexy. As in many of our surgical procedures, the approach to retinal detachment repair has undergone numerous evolutions over the years.

From the initial SB and larger gauge vitrectomy procedures, we now have small-gauge vitrectomy systems that enable greater precision and maneuverability in the eye and around pathology. Vitreous cutters are becoming faster with enhanced technology to potentially increase surgical safety while optimizing efficiency. Surgical visualization platforms are improving. This includes wide-field visualization systems that provide incredible views of the retinal periphery. Digital 3D systems now provide new opportunities for enhanced visualization. All of these technologies, likely combined with reduction in SB training, have enabled this transition toward primary vitrectomy for the management of retinal detachment repair.

With concerns of PVR and maximizing tractional relief, careful and potentially extensive vitreous base shaving has been traditionally advocated as the standard approach to primary vitrectomy for retinal detachment. In fact, studies have suggested that primary vitrectomy may be more advantageous in pseudophakic eyes compared to phakic eyes. One possibility for this advantage is the limited access to the anterior vitreous base in phakic eyes that may result in a higher risk of PVR.

The dynamic surgical considerations of vitreous removal reminds me of a similar evolution with endolaser utilization during primary vitrectomy for retinal detachment. Early in the transition away from using SB, many surgeons favored 360-degree laser retinopexy at the time of retinal detachment repair. Some studies have suggested this approach may improve surgical outcomes.9,10 However, more recently, surgeons have started to take a much more minimalist approach, treating just the sector of the retinal detachment or simply treating the breaks identified during surgical repair11 Studies have been published in favor of both approaches making a conclusive decision difficult.

In considering the approach to vitreous removal, one key challenge is that regardless of how we handle the vitreous, we have evidence that minimal to no vitreous removal may be necessary, such as in pneumatic retinopexy. With optimal case selection, pneumatic retinopexy can have an excellent success rate without removing any vitreous at the time of retinal detachment repair. The critical aspects of success are treating all retinal breaks and closing the causative breaks with a gas tamponade. In that context, it is not surprising that a high percentage of eyes could do quite well following vitrectomy without scleral depressed vitreous base shaving. In fact, a recent surgical technique report described an 89% single surgery success rate of limited vitrectomy in pseudophakic eyes with retinal detachment. In these cases, a core vitrectomy was performed with limited peripheral vitreous shaving, including refraining from removing the flap of the tear.12 Limiting peripheral vitreous base shaving with scleral depression may also have advantages from a safety standpoint in potentially reducing risk of iatrogenic breaks or unintended lens trauma.

I believe that there is tremendous case-to-case variability in vitreous characteristics, in retinal detachment tissue dynamics, and in the ability to successfully remove a large amount of the peripheral vitreous without scleral depression. In pseudophakic eyes with optimal peripheral visualization, careful initial vitrectomy may result in extensive vitreous removal with only small amounts of residual vitreous accessible for removal during scleral depression. There are important challenges for drawing strong conclusions from many of these studies, including the high case variation and significant surgeon variability that may influence outcomes.

Separate from whether vitreous base shaving is necessary, intraoperative scleral depression for identification of retinal breaks is likely still a critical piece of optimal surgical management. What many of these studies appear to confirm is that we have many ways to successfully manage and treat retinal detachments. As more data emerge, our surgical technology continues to expand, and potentially new therapeutics are developed for minimizing PVR risk, the approach to vitrectomy in retinal detachment repairs will likely continue to evolve. RP

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