Hydrogel-based ocular drug delivery systems

Ocular drug delivery is challenging due to physical and physiological barriers, such as the corneal epithelium and blood-retinal barrier, resulting in limited bioavailability (<5% for eye drops) and fast degradation. For the reason of improving drug delivery to the anterior and posterior ocular segments, this review attempts to assess hydrogel-based systems as versatile systems to overcome these barriers. We thoroughly explore physicochemical and performance characterization approaches (e.g., swelling, rheology, drug release kinetics), hydrogel fabrication methods (e.g., chemical crosslinking, 3D printing), and their uses in new and commercial products. Significant advances highlight the controlled release, mucoadhesion, and biocompatibility of hydrogels, which allow prolonged drug delivery as demonstrated by commercial products such as DEXTENZA® and ReSure® Sealant for corneal sealing and post-operative inflammation control. New technologies provide greater accuracy and less invasiveness. Examples include bioengineered hydrogels for retinal regeneration, systems integrated with nanotechnology, and stimuli-responsive hydrogels (such as pH-sensitive chitosan for glaucoma). By addressing mechanical stability and regulatory criteria, characterization techniques guarantee the suitability of the hydrogel for ocular applications. Hydrogels exhibit considerable promise for personal and least invasive treatments, despite challenges like scalability and high production costs. With implications for improving clinical outcomes and patient compliance through novel biomaterials, this review highlights the important role of hydrogels in ocular drug delivery and offers an outline for future advancements in the treatment of diseases like glaucoma, age-related macular degeneration, and dry eye syndrome.