Eye On Innovation: A Comparative Review on Ocular Inserts and Eye Gel for Enhanced Therapeutic Efficacy and Better Ocular Drug Delivery

Ocular drug delivery remains a major challenge in pharmaceutical research due to anatomical and physiological barriers such as tear turnover, nasolacrimal drainage, and corneal impermeability, which limit bioavailability of conventional eye drops to less than 5%. Sustained release formulations like ocular inserts and eye gels have emerged as innovative alternatives to overcome these limitations. Eye gels, particularly in-situ gelling systems, prolong precorneal residence time, enhance patient comfort, and improve therapeutic efficacy by offering diffusion-controlled or zero-order release. Ocular inserts, available in erodible and non-erodible forms, provide precise dosing, significantly higher tissue absorption, and extended release lasting from hours to several days. Comparative studies demonstrate that ocular inserts generally achieve superior bioavailability and therapeutic outcomes, including up to 42-fold higher tissue concentrations, while eye gels offer better patient compliance and ease of application. Advances in polymers, nanocarriers, 3D printing, and hybrid systems continue to expand the potential of both approaches. This review critically evaluates inserts and gels with respect to release kinetics, bioavailability, therapeutic efficacy, stability, irritation profile, shelf-life, and manufacturing costs, providing an updated perspective on which formulation may offer optimal ocular drug delivery for long-term therapy.