Overcoming anatomical and physiological barriers to reaching the retina

Drug delivery to the posterior segment of the eye is significantly more difficult than to the anterior segment. Currently, topical drug delivery is only available for the latter due to anatomical and physiological constraints. Posterior drug delivery, on the other hand, typically involves intravitreal injections (IVT) to reach the retina. Therapeutic efficacy post-injection is only maintained for a short period of time. As such, those prescribed IVT receive monthly or bimonthly injections while facing potential risks of infections and vision loss, leading to low compliance.

There are two main ways to reduce patient burdens: minimizing the frequency of IVT or innovating non-invasive delivery systems. Recent breakthroughs in polymer science have made realizing these non-invasive treatment pathways possible, but their clinical application remains elusive. Noting this gap, Wang et al. reviewed current advancements in polymer science for developing safe, effective, and patient-friendly retinal disease therapeutics.

“We are framing polymer-based delivery not just as a technical innovation but as a translational strategy aligned with clinical needs in retinal diseases,” said author Zengping Liu. “Our review systematically compares sustained-release intravitreal systems, emerging topical formulations, and unconventional delivery routes such as suprachoroidal and subretinal access. This synthesis reveals not only what works presently but also what could soon reshape the treatment landscape.”

The authors are investigating promising retinal disease therapeutics in future works.

“We’re excited to explore our upcoming projects that will likely focus on hybrid delivery systems combining gene therapy and polymers — especially the innovative biodegradable nanoparticles that can co-deliver genetic material alongside anti-angiogenic drugs,” which stop new blood vessel growth, said Liu. “Spatially targeted delivery, made possible by advances in imaging and microneedle technology, is also an exciting new frontier.”

Source: “Recent advancements in polymer science for retinal diseases: New frontiers in drug delivery systems,” by Weiliang Wang, Nancy Wang, Xinxin Zhao, Xinyi Su, and Zengping Liu, APL Bioengineering (2025). The article can be accessed at https://doi.org/10.1063/5.0264382 .