CONTROLLED AND TARGATED DRUG DELIVERY SYSTEM FOR OCULUAR DISEASE

Abstract

The drug delivery is highly challenging due to the presence of anatomical and physiological barriers that limit drug absorption and therapeutic effectiveness. These barriers, classified as static (corneal epithelium, blood–ocular barrier) and dynamic (tear turnover, blinking, nasolacrimal drainage), significantly reduce drug bioavailability. As a result, conventional ocular dosage forms such as eye drops show poor drug retention and require frequent administration. The human eye possesses unique structural and functional characteristics that hinder drug penetration into targeted tissues. Although topical administration is the most convenient and patient-compliant route, especially for anterior segment diseases, it provides limited therapeutic concentrations for extended periods. More than 95% of marketed ophthalmic products are liquid formulations, yet their effectiveness is restricted by rapid precorneal elimination. To overcome these limitations, advanced drug delivery systems such as intravitreal implants, biodegradable and non-biodegradable polymeric systems, nanoparticles, in situ gels, and viscosity-enhanced formulations have been developed. These systems aim to prolong drug residence time, provide controlled and sustained release, reduce dosing frequency, and improve patient compliance. Recent advancements focus on enhancing ocular permeation and achieving targeted drug delivery, thereby improving therapeutic outcomes in chronic ocular diseases.