The applications of viscoelastic agents in vitreoretinal surgery

The introduction of viscoelastics in human ocular surgery dates back to 1972.Subsequntly, several substances were proposed as adjuvants, particularly for cataract surgery; however, the rheologic properties of ophthalmic viscosurgical devices (OVDs), such as viscosity, pseudoplasticity, and coatability led to their employment also in vitreoretinal surgery. OVDs can be used to separate tissues and create space, to break adhesions, to allow space for surgical manipulation, and to contain hemorrhage by dampening capillary oozing. We focus on the principles and clinical results of several viscosurgery techniques, such as viscodissection and viscodelamination for the management of proliferative vitreoretinopathy and diabetic retinopathy and suprachoroidal buckling for primary retinal detachment. Furthermore, we analyze the techniques in which OVDs served as adjuvants in macular hole surgery, particularly in the handling of the internal limiting membrane, and as volumetric substances against hypotony. Finally, we analyze recent perspectives on vitreous humor biochemical features. Preclinical research led to the belief that hyaluronic acid-based hydrogels could become ideal vitreous substitutes, thanks to their viscoelasticity, porosity, optical properties, and biocompatibility; however, although promising, long-term toxicity issues have limited studies on human subjects.