Background and objective: To investigate the surgical feasibility and safety of a long-term intravitreal triamcinolone acetonide (TA) sustained delivery system.
Materials and methods: Pigmented rabbits were implanted with sustained-release formulations containing 925 microg of TA within a non-biodegradable polymer coating: Dose A (n = 15) with a slow delivery rate of 1 to 2 microg/day and Dose B (n = 15) releasing 3 to 5 microg/day. Additionally, a control group (n = 10) using a device coated with polymer only was implanted. The devices were surgically implanted through a 30-gauge sclerotomy into the vitreous cavity. The animals were clinically observed for up to 6 months after the surgery with complete ophthalmologic examinations. Histologic evaluation of a subset of eyes was performed at the conclusion of the study.
Results: Implants were successfully implanted in all 40 eyes. Ocular examinations revealed excellent implant tolerability. In all eyes, there was no significant postoperative inflammation at 1 week of follow-up. There was no increase in intraocular pressure during the follow-up period and histologic evaluation demonstrated no significant abnormalities. Minimal and localized vitreous hemorrhage was observed in 22.5% of implanted eyes and mostly cleared at 1 month after surgery. During the 6 months of follow up, localized lens opacities associated with physical implant contact developed in 66.6% of eyes.
Conclusion: The surgical procedure using the intravitreal TA sustained delivery device is feasible. Surgical complications were generally mild, with lens opacities attributable to unique anatomical features of the rabbit eye. Long-term follow-up and histology revealed excellent implant tolerability.