Convection‐assisted intra‐vitreous drug delivery in human eye: An experimental investigation

Abstract

AbstractWe report an in vitro transient experimental study of the human eye to determine the effects of convection on the transport of drugs from the point of injection to the retinal surface through the fluid in the vitrectomized eye. The human eye is modeled as a glass orb of realistic proportions, and water and silicone oil mimic the vitreous fluid. In a series of experiments, the dye that is used to mimic the drug is injected at two different spots in the vitreous chamber, and its transport through the vitreous fluid mimic to the retinal surface is recorded under conditions of simple diffusion and convection‐assisted diffusion. The drug concentrations at two different spots on the retinal surface at different times are monitored. It is shown that the drug reaches all parts of the retinal surface much faster during convection‐assisted diffusion than during pure diffusion, irrespective of where it is injected in the cavity. In a snapshot, it is seen that the dye concentration reaches at the target central retinal pigmented epithelium spot in just 12 min (0.2 h) with convection‐assisted diffusion as against 12 h in pure diffusion. The steady‐state average drug concentration at the target retinal region is seen to be 56.25 times greater for the convection‐assisted drug transport than for the pure diffusion case. The results show that applying mild heat to the retinal surface by methods such as laser irradiation can induce convection‐based transport of the drug in the vitreous fluid. This method makes the drug available much faster at the target retinal region than drug transport by pure diffusion. The faster transport of the drug within the cavity can expedite the drug's effect and prevent drug loss due to delays.