Biodegradable scleral implant for intravitreal controlled release of ganciclovir

Background: The aims of this study were to develop biodegradable scleral im plants that could overcome previously reported disadvantages such as an adv erse burst in the late phase of release and to investigate the release prof ile of modified scleral implants in vitro and in vivo. Methods: The modifie d scleral implants (weight 8.5 mg, length 5 mm) were made of mixtures of po ly(DL-lactide) (PLA) with different molecular weights and contained 25 weig ht % of ganciclovir (GCV). The release of GCV was evaluated in vitro by spe ctrophotometry. Intravitreal GCV concentrations in vivo were measured by hi gh performance liquid chromatography following plug implantation in pigment ed rabbits. The biocompatibility of the device was determined by indirect o phthalmoscopy and light microscopy. Results: The in vitro release studies s howed stable, longterm sustained and slow release. The in vivo release stud ies showed that the implants had long-term release in the diffusional phase of the triphasic release pattern and only a minor adverse burst of GCV in the late phase. No significant retinal toxicity was observed by histologic examination. Conclusion: Our findings showed that this newly modified scler al implant may provide suitable intravitreal drug delivery for treatment of cytomegalovirus retinitis.