Computer modeling of drug delivery in the anterior human eye after subconjunctival and episcleral implantation

Recently, subconjunctival and episcleral implants have been proposed in the treatment of anterior eye diseases. In order to improve the delivery efficacy, it is important to understand the transport process of the implanted drugs. A 3D computational model, which includes heat transfer, aqueous humor (AH) flow, as well as diffusive and convective transport of the drug concentration, is developed to study the temporal and spatial evolution of the drug in the anterior segment of a human eye after subconjunctival and episcleral implantation, with a focus on drug delivery to three targets: iris, lens, and trabecular meshwork (TM). The release rate of the implanted drug is based on experimental data and effects of implantation location, eye orientation, and AH flow are investigated. Our numerical results indicate that subconjunctival implantation is more effective than episcleral implantation for drug delivery to all the three targets, and the accumulative amount of drug delivered to the three targets is larger in the horizontally-facing eye than in the up-facing eye. Implantation at the 12 o'clock circumferential position is the most effective for drug delivery to iris and lens, and the 3 o'clock position is the most effective for drug delivery to TM. This study may help to better understand the delivery process of implanted drugs in the anterior human eye, and improve delivery efficacy for clinical treatment of anterior eye diseases.