Novel Vitreous Substitutes in Vitreoretinal Surgery

Abstract and Introduction

Abstract

Purpose of Review: After removing the native vitreous during vitreoretinal surgery, an adequate substitute is required to ensure homeostasis of the eye. Current clinically used endotamponades (silicone oil, gases, semifluorinated alkanes) are effective in promoting retinal reattachment, but lead to complications such as emulsification, prolonged inflammation, blurred vision, raised intraocular pressure, cataract formation or the need for revision surgery. The aim of this review is to provide an update on novel vitreous substitutes with a focus on polymer-based systems.

Recent Findings: Polymeric hydrogels provide favourable properties such as high water content, optical transparency, suitable refractive indices and densities, adjustable rheological properties, injectability, biocompatibility and their ability to tamponade the retina via viscosity and swelling pressure, comparable to the native human vitreous body. Here, vitreous replacement strategies can be divided into chemically or physically crosslinked hydrogel systems that are applied as preformed or in-situ gelling matrices.

Summary: Several hydrogel-based vitreous substitutes have already been positively evaluated in preclinical tests and have the potential to enter the clinical phase soon.

Introduction

The native vitreous body is a hydrophilic matrix that is of great importance in terms of the embryogenesis of the eye, the tamponading properties in the first decades of life, the maintenance of homeostasis in the eye and its manifold interactions with neighbouring structures. During the treatment of vitreoretinal pathologies such as retinal detachments, the vitreous body needs to be removed (vitrectomy) and the retina is stabilized with an endotamponade. In current clinical use, silicone oils,^[1] semifluorinated alkanes (e.g. C₈F₁₈, F₄H₅)^[2,3] and gases (e.g. SF₆, air)^[4–7] are utilized as tamponading fillers after the removal of the native vitreous. Current clinically used endotamponades are effective in promoting retinal reattachment, but deviate from the hydrophilicity, refractive index and density of human vitreous, leading to complications such as emulsification, prolonged inflammation, blurred vision, raised intraocular pressure, cataract formation or the need for revision surgery. Recent tamponade strategies therefore aim at hydrophilic, hydrogel-based systems because of their favourable properties such as high water content, optical transparency, suitable refractive indices and densities, adjustable rheological properties, injectability, biocompatibility and their ability to tamponade the retina via viscosity and swelling pressure. Recent reviews affirm the relevance and need for new vitreous replacement strategies.^[8–13] The following review will provide an update on new vitreous substitutes with a focus on polymer-based systems (for systematic literature review see Supplementary Information, http://links.lww.com/COOP/A39).