Treating retinal diseases such age age-related macular degeneration (AMD) is often a long and challenging road. Patients struggle with adherence to treatment for many reasons, including its invasiveness and continual retreatment regimen. A new refillable drug delivery system for retinal conditions shows promise as a long-term treatment and an alterative to more invasive options, a new study reports.

The drug-refillable system—which could be used to treat conditions such as AMD—has a silicone reservoir and an injectable gelatin/chitosan gel. Through a computer-aided design, investigators fit the silicone reservoir, which allows micropores to be released to the sclera. Additional features of the system include a stainless steel wire and sheet in the side and bottom of the reservoir that helps to ensure it fits on the curvature of the eye and prevents irritation to the sclera, the study noted.

After injecting the reservoir with the gelatin/chitosan gel, the researchers found the release rate from the encapsulated gel in the reservoir was slower than the original release. After re-injecting the reservoir with more gel, the study found the same release profile as the first injection.

Investigators placed the reservoir on the sclera of a rabbit and then studied the distribution of fluorescein in the retina and choroid/retinal pigment epithelium (choroid/RPE). Continued presence of fluorescein during the 12 weeks of implantation indicated that the device successfully delivered the drug to the retina.

The researchers were able to successfully refill the reservoir using an injection through the conjunctiva, investigators noted.

“In conclusion, the refillable drug delivery device is a promising tool to administer drugs long-term by reinjection with less invasiveness to intraocular tissues,” the researchers wrote in their paper. 

Ngai N, Saijo S, Song Y, et al. A drug refillable device for transscleral sustained drug delivery to the retina. Eur J Pharm Biophar. 2019;136:184-91.