ABSTRACT

Ocular drug delivery faces significant challenges due to the eye’s complex structure and protective barriers that limit effective drug penetration and bioavailability. Conventional delivery routes such as topical, systemic, periocular, and intravitreal administration exhibit varying degrees of therapeutic benefit, although each of them is restricted by different factors like rapid tear clearance, corneal impermeability, systemic toxicity, or procedural invasiveness. These obstructions have restricted the development of advanced ocular drug-delivery technologies to enhance drug residence time, target specificity, and patient compliance. Nanocarrier systems, including liposomes, nanoparticles, and micelles, improve solubility, permeability, and controlled release parameters, while in situ gelling systems and drug-eluting contact lenses show sustained, non-invasive delivery options. Ocular implants posses long-term posterior segment therapy, but includes surgical insertion. Innovative techniques like microneedle patches allow for targeted, less invasive distribution, bridging the gap between topical and intravitreal techniques. Despite persistent issues with safety and longevity, gene and cell-based therapies show promise for long-lasting, possibly curative therapy of degenerative and chronic ocular disorders. Future developments for the area will focus on long-acting formulations, personalised ophthalmic medicine, enhanced non-invasive procedures, and smart delivery platforms . When taken as a whole, these developments will reduce long-standing obstacles and revolutionize treatment approaches for ocular illnesses of the anterior and posterior segments.