Liposomal Drug Delivery in Ocular Therapy: Strategies for Enhancing Corneal Penetration and Bioavailability.

Vision impairment affects approximately 2.2 billion people worldwide, with glaucoma, age-related macular degeneration, fungal keratitis, and diabetic retinopathy among the leading causes of preventable blindness. Effective pharmacotherapy remains severely constrained by the eye's multilayered barrier architecture. Tear film, the corneal epithelium, the blood-aqueous barrier, and the blood-retinal barrier collectively restrict conventional topical drug bioavailability to less than 5% of the administered dose. Liposomal drug delivery systems have emerged as a clinically translatable platform capable of overcoming these barriers through targeted surface modification. This review provides a brief introduction to ocular barriers to drug delivery and transport and critically examines numerous surface-modification strategies applied to liposomal carriers to enhance corneal permeation and ocular bioavailability of drugs. It highlights the advantages and disadvantages of each modification strategy, as well as the convergent mechanism of liposomal surface modification in overcoming ocular barriers, and provides a comparative analysis of different surface-modification strategies of liposomes in terms of safety, efficacy and corneal retention. Additionally, it describes challenges associated with liposomal ophthalmic formulations in industrial scaling up. The review also sheds light on some FDA-approved liposomal ophthalmic products, active clinical trials on liposomal formulations, and relevant patents, demonstrating the potential benefits of liposomal drug delivery in the treatment of ocular disorders.