Pharmacologic vitreolysis with microplasmin increases vitreous diffusion coefficients

Background Pharmacologic vitreolysis is a new approach to improve vitreo-retinal surgery and ultimately to liquefy and detach the vitreous from the retina to eliminate the contribution of the vitreous to retinopathy. The mechanism of action of the agents being developed for pharmacologic vitreolysis remains unclear. The effect of microplasmin on vitreous diffusion coefficients was investigated using the non-invasive technique of dynamic light scattering (DLS). Methods Vitreous diffusion coefficients in 18 intact porcine eyes were measured in vitro with dynamic light scattering (DLS). DLS was performed on all specimens at 37 degrees C 30 min after injections of human recombinant microplasmin at doses ranging from 0.125 to 0.8 mg, with 20-nm tracer nanospheres. Results DLS findings in untreated porcine vitreous were similar to the previously described findings in bovine and human vitreous. Microplasmin increased porcine vitreous diffusion coefficients in a dose-dependent manner (correlation coefficient, r=0.93), with an 85% increase after a 30-min exposure to the maximum dose. Conclusions Pharmacologic vitreolysis with human recombinant microplasmin increases vitreous diffusion coefficients in vitro. The results of these studies have implications for the dosing, route of administration, duration of action and methods of determining efficacy in future studies of pharmacologic vitreolysis to enhance vitreo-retinal surgery, as well as the design of clinical trials to induce prophylactic posterior vitreous detachment.