Recent Advances in Extended Ocular Drug Delivery for the Ocular Surface

The unique anatomy and physiological barriers of the human eye-particularly rapid tear turnover and limited corneal permeability-present significant obstacles to achieving effective topical drug delivery. In response to these constraints, biopolymer-based extended-release systems have emerged as a promising and transformative class of ocular therapeutics. This review provides a comprehensive overview of recent advances in natural biopolymers, including polysaccharides and protein-derived polymers, for application on the ocular surface. These materials exhibit advantageous characteristics such as mucoadhesion, biocompatibility, and stimuli-responsive behavior, which collectively enhance precorneal residence time and enable controlled, sustained drug release. We further discuss diverse delivery platforms-ranging from in situ forming hydrogels and mucoadhesive nanoparticles to drug-eluting contact lenses and microneedle-based systems. In addition, we highlight how the integration of nanotechnology and bioinspired scaffolds can augment the delivery efficiency of therapeutic agents to ocular tissues. Overall, this review underscores the ongoing transition from conventional topical eye drops to sophisticated, functionalized delivery systems capable of maintaining therapeutic drug levels while simultaneously supporting tissue repair and wound healing. Finally, we outline the remaining challenges in clinical translation and consider the future potential of smart, responsive biopolymer systems in advancing the treatment of both anterior and posterior segment diseases.