Advanced Ocular Drug Delivery Systems and Therapeutic Innovations in Ophthalmic Pharmacy: A Comprehensive Critical Review

Conventional ophthalmic formulations, primarily topical eye drops, face severe therapeutic limitations due to highly efficient ocular anatomical and physiological barriers. Rapid nasolacrimal drainage, corneal epithelial tight junctions, and metabolic clearance result in exceptionally low ocular bioavailability (<5%), necessitating frequent high-dose administrations that induce significant systemic side effects and poor patient compliance. This comprehensive review examines the current challenges in ocular pharmacokinetics and evaluates state-of-the-art technological innovations designed to overcome these barriers. We discuss advanced nanomedicine platforms including liposomes, polymeric nanoparticles, solid lipid nanoparticles (SLNs), and nanoemulsions, which enhance corneal residence time and targeted tissue penetration. Furthermore, we analyze groundbreaking structural innovations such as drug-eluting contact lenses, in situ forming hydrogels, and microneedle arrays that enable controlled, zero-order release kinetics for both anterior and posterior segment diseases. Finally, this article highlights emerging paradigms in ophthalmic pharmacy, including artificial intelligence-driven formulation design, 3D-printed personalized ocular therapeutics, and gene delivery systems, charting a clear roadmap for the translation of next-generation ocular pharmacotherapy from bench to bedside.