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.

Biomechanical properties of retina and choroid: a comprehensive review of techniques and translational relevance

“…Knowing the cantilever stiffness, the Young's modulus of the samples can be calculated from the deflection of the cantilever as it indents points on the sample surface. AFM has been used to assess thickness [54,55] and a range of ILM biomechanical parameters, namely anisotropy [28,[55][56][57][58], indentation rate sensitivity and hysteresis [28], developmental and agedependent stiffness variations [54,59], as well as stiffness changes due to disease [28,60] and treatments, such as tissue staining [57,58] and glycosaminoglycan removal [54]. While AFM is restricted to scanning small areas in the region of 150 × 150 × 20 µm, the primary advantage of this technique is its ability to measure properties of nanoscale structures such as cells, collagen and nerve fibres.…”

Retinal Tectonics after Macular Pucker Surgery: Thickness Changes and En-Face Displacement Recovery

“…Although the functional benefit of ILM peeling performed in our series, compared with ERM stripping alone, remains uncertain, 19 from the mechanical standpoint, ILM removal is very likely to trigger significant retinal adjustments because the ILM is a stiff structure 20 whose properties change after peeling and also with staining. 21 A recent meta-analysis reported a significantly thicker postoperative fovea in patients undergoing ILM peeling compared with ERM peeling alone.…”

“…Finally, we should acknowledge that the concept of surgery as a mechanism of restitutio ad int egrum is misleading: With all the uncertainties of biomechanical measures, the properties of the entire retina, 30 isolated ILM, 20 and ERM 31 are significantly different and span two orders of magnitude; stripping the ERM and ILM from the retinal surface means removing thick and stiff structures adherent to the retina, thus macroscopically altering the balance of forces. By no means, this can be simplified as “rewinding” the course of disease.…”

Sensing red blood cell nano-mechanics: Toward a novel blood biomarker for Alzheimer’s disease

“…In the last decades, a large body of evidence has emerged that—along with biochemical and genetic cues—mechanical stimuli are critical regulators in human physiology, as well as fundamental players in the onset and the progression of many pathological states ( Kumar and Weaver, 2009 ; Lu et al, 2011 ; Van Zwieten et al, 2014 ; Ciasca et al, 2016a , 2019 ; Vielmuth et al, 2016 ; Weaver, 2017 ; Perini et al, 2019 ; De-Giorgio et al, 2020 ; Di Giacinto et al, 2020 ; Mazzini et al, 2020 ). A wide range of diseases that bring patients to the doctor’s office can be, indeed, associated with significant alterations in the mechanical properties of cells, tissues, and organs.…”