Comparison of Drug Distribution Between Intravitreal Injection and a Controlled–Release Implant in a Rabbit Eye

Due to physiological barriers within the eye, which limit penetration of many drugs from the systemic circulation into the vitreous, the most common method of treating retinal disease is direct intravitreal injection. However, this common procedure may be inappropriate for a wide range of drugs as it may lead to highly variable concentrations potentially causing higher toxicity for tissues inside the eye and limiting therapeutic effect. A recent procedure is to use surgically implanted drug release device, called implant here, in the vitreous of the eye that allow controlled release of drug over a sustained period of time. For constant release of drug over 15 hours, a substantial reduction in peak drug concentration is predicted near the retina. When compared with the implant, a doubling of drug concentration would be expected for more than 3 hours near the retina for the intravitreal injection.