Nanotechnological Advances in Ocular Therapeutics: A Narrative Review of Drug Delivery Platforms, Clinical...

Nanotechnology-based ocular drug delivery systems offer a promising approach to overcoming the anatomical and physiological barriers that limit the efficacy of conventional ophthalmic formulations, where topical bioavailability typically remains below 5% owing to rapid nasolacrimal drainage, precorneal tear turnover, and corneal impermeability. This narrative review synthesises current evidence on nanocarrier design, delivery pathways, and disease-specific therapeutic applications, incorporating cross-platform comparison across six nanocarrier systems and explicit stratification of evidence by translational stage.

A structured narrative review was conducted using OVID MEDLINE, Embase, Scopus, Web of Science, and PubMed from database inception to September 2025, supplemented by citation chaining and targeted Google Scholar searches. Data extraction focused on carrier architecture, drug-loading and release characteristics, delivery routes, mechanistic behaviour, therapeutic outcomes, and safety profiles. This review was conducted in accordance with the general principles for narrative reviews as described in the Scale for the Assessment of Narrative Review Articles (SANRA).

Key nanocarrier classes included liposomes, polymeric micelles, dendrimers, nanosuspensions, nanoemulsions, and chitosan- and protein-based nanoparticles. Compared with conventional formulations, these systems demonstrated improved corneal residence, enhanced mucoadhesion, increased transscleral diffusion, reduced dosing frequency, and sustained intraocular exposure. Clinically translated examples include cyclosporine A nanomicelle and nanoemulsion formulations, marketed as Cequa (0.09%), Restasis (0.05%), and Ikervis (0.1%), approved for dry eye disease, and a subconjunctival PLGA nanoparticle depot that achieved greater than 20% intraocular pressure reduction sustained over 90 days from a single injection in early clinical evaluation. Applications spanned anterior-segment disorders, including dry eye disease, conjunctivitis, infectious keratitis, ocular inflammation, and glaucoma, and posterior-segment diseases such as diabetic retinopathy, age-related macular degeneration, retinoblastoma, and retinopathy of prematurity.

Lipid-based and polymeric nanocarrier platforms are currently closest to clinical translation, with approved formulations and early-phase trial data supporting meaningful therapeutic advantages over conventional delivery. Realising the full potential of ocular nanomedicine will require addressing residual challenges in long-term ocular safety, manufacturing scalability, and regulatory compliance, particularly for posterior-segment applications, where non-invasive topical delivery remains largely at the preclinical stage.