In their study entitled “Effect of Serial Intrasilicone Oil Bevacizumab Injections in Eyes With Recurrent Proliferative Vitreoretinopathy Retinal Detachment,” Hsu and associates evaluate the possible role of bevacizumab in preventing postoperative proliferative vitreoretinopathy (PVR) and its related complications. However, their study could not ascertain any beneficial effect of serial monthly intrasilicone oil injections of bevacizumab.
The hypothesis of the current study was based on the proven competitive inhibition of platelet-derived growth factor (PDGF) by binding of vascular endothelial growth factor (VEGF) on its receptors. However, it must be remembered that these studies, along with the others cited by the authors regarding efficacy of anti-VEGF therapy in preventing PVR in rabbits, are all based on vitreous-filled eyes or the rabbit vitreous itself. As 10 of the 20 patients in the study group had undergone previous vitrectomy, absence of vitreous becomes a confounding factor and may have affected the results. Vitrectomized eyes with retinal detachment are badly inflamed and more susceptible to PVR. This ambiguity in the study may be neutralized by assessing these 10 patients against those who had undergone only scleral buckling as the initial procedure.
The authors have considered dosage or wrong scheduling along with presence of silicone oil as the reason for inability to achieve therapeutic effect. Further, they discuss that “once the cascade of inflammatory events has reached a threshold, use of anti-VEGF antibodies is insufficient to halt the profibrotic process.” Similarly, a feedback loop for VEGF production and nonperfusion has been hypothesized previously for VEGF-related macular edema in retinal vein occlusion after delaying of treatment. Hence this may reiterate presence of a window for treatment beyond which failure of drug effect would be seen, as was the case in the current study, where the initiation period was more than a month after the disease onset. Also, as epiretinal membrane (ERM) formation post vitrectomy could be associated with vitreous hyalocytes left behind after surgery in cases of anomalous posterior vitreous detachment, considering ERM formation as a parameter might yield negative results too.
As PVR is a serious complication of retinal detachment and a common culprit for redetachment post surgery, any medical therapy against it would be most welcomed. In this regard, PDGF antagonists are being studied for neovascular macular degeneration and may have a role in managing PVR as well.