We 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 a 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 various times are monitored.
An in-vitro transient numerical simulation of the human eye is performed to determine the effects of vitreous convection on the transport of drugs to the retinal surface. The convection of the fluid in the vitrectomized eye induced by a laser-induced spot heating of the retinal surface during intravitreal administration of the drug is modeled. The three-dimensional computational model used is based on the physiological dimensions of the human eye. Drug transport is numerically simulated by solving suitable transient mass momentum and species conservation equations accounting for the natural convection flow of the vitreous humor. The vitreous body is studied in its age-related liquefaction state and during retinal surgery.
It is observed from the preliminary simulations that the dye concentration reaches 13μg/mL at the target central retinal pigmented epithelium (RPE) spot in just 10 min (0.16 h) with convection-assisted diffusion, in contrast to the 13.5 hours for pure diffusion. This finding is corroborated by experimental data. The significantly faster drug delivery to the target spot, facilitated by vitreous humor convection under specific conditions, can enable faster and more efficient retinal treatment outcomes.