Comment on the Article: Subretinal Bleb of Voretigene Neparvovec.

Abstract

To the Editor: We studied with great interest the article Subretinal Bleb of Voretigene Neparvovec by João Pedro Marques et al.1 Demonstrating new ways of sub-retinal bleb formation in the process of voretigene neparvovec application provides important upgrades of the surgical technique.1 However, we would like to address some potential bias of the surgical protocol that may confound the final outcomes and propose an alternate approach based on our own experience. We hypothesize that performing only one bleb in the process of subretinal voretigene application, following a saline prebleb, could lead to perifoveal chorioretinal atrophy. Utilizing saline in the process of pre-bleb formation, dilutes the concentration of the vector and possibly lowers the risk of toxicity2 but calls the efficacy in question on the other hand. The concept of creating only a single bleb and accordingly, instilling the total volume of the drug subretinally, carries a higher risk of foveal rupture due to uncontrolled and excessive retinal stretching. Furthermore, completely detached fovea could be mis-located during the ensuing process of subretinal voretigene neparvovec resorption. Thus, to deliver the total amount of the prescribed volume, it seems rational to distribute it to more than a single bleb. Performing more than one bleb lowers the volume of voretigene neparvovec within a single bleb, and additionally, prevents the detachment of the fovea. Finalization with a fluid-air exchange in the vitreous cavity provides both tamponade and allows a gentler and more favorable subretinal spreading of the drug into the subfoveal space compared to dynamically robust separation of the retinal neuroepithelium by subretinal instillation of the total drug volume in a single shot either manually or by subretinal injector with viscous fluid injection. Leon Marković, MD*† Damir Bosnar, MD, PhD*†‡ Mirjana Bjeloš, MD, PhD*†‡