Nagai is leading a group of researchers based at the Division of Clinical Cell Therapy who are working to develop therapies in intractable retinal diseases, specifically a transscleral sustained drug release device. This aim is not without its problems as there are several barriers regarding our current knowledge about transscleral sustained drug release. "There are many types of drug delivery systems for posterior segment eye diseases treatment, and some of them are applied clinically," outlines Nagai. "But, all of the drug delivery system (DDS) applied clinically are intraocular DDS, that is, intravitreal implants. They require surgical procedures to implant the devices in the vitreous or the retina, which can cause severe complications in the eye." Thus, in the context of invasiveness, transscleral drug delivery is a better route, because no incision of the eyeball is required. The treatment is simply administered through placing a device on the eye. However, few transscleral drug delivery systems have been developed up until now, with one of the chief reasons being the availability of specific drugs through the transscleral route. "In order to be effective, the drugs must pass through the sclera, choroid circulation, and retinal pigment epithelium barrier to the retina," says Nagai. "As it stands, pharmacokinetic studies regarding transscleral DDS have proved challenging and there are many reports attesting to this.