Biomechanical Properties of the Internal Limiting Membrane after Intravitreal Ocriplasmin Treatment

Abstract

Purpose: To assess the stiffness of the human internal limiting membrane (ILM) and evaluate potential changes of mechanical properties following intravitreal ocriplasmin injection for vitreomacular traction. Methods: This is an interventional comparative case series of 12 surgically excised ILM specimens consecutively obtained from 9 eyes of 9 patients after unsuccessful pharmacologic vitreolysis with ocriplasmin. During the same time period, 16 specimens from 13 other eyes without ocriplasmin treatment were harvested during vitrectomy and served as controls. All patients presented with macular holes or vitreomacular traction and underwent vitrectomy with ILM peeling either with or without brilliant blue (BB) staining. All specimens were analyzed using atomic force microscopy with scan regions of 25 × 25 μm. In all specimens, both the retinal side and vitreal side of the ILM were analyzed. Results: Atomic force microscopy revealed no significant differences in elasticity of ILM specimens removed from eyes with or without ocriplasmin treatment. Undulated areas of the retinal side presented stiffer than the vitreal side of the ILM. Topographical mapping of both the vitreal and retinal side of the ILM showed no apparent alteration of the morphology in ocriplasmin-treated eyes compared to untreated eyes. Staining with BB resulted in an increase of tissue stiffness. Conclusions: Intravitreal injection of ocriplasmin does not change biomechanical properties of the human ILM. There is no evidence of a potential enzymatic effect of ocriplasmin interfering with the stiffness of this basement membrane.