Implication of microneedles for ocular drug delivery systems

Long-term pharmaceutical therapy is often essential for managing inflammatory and proliferative ocular diseases. Traditional treatments, such as eye ointments or drops, face limitations like frequent administration, restricted bioavailability, and challenges in overcoming ocular barriers. Direct injection into ocular tissues is a common clinical practice to address barrier properties. However, injections pose significant tissue injury risks and are associated with unfavorable side effects, leading to poor patient compliance. Innovative distribution mechanisms are imperative to overcome these challenges. Microneedles, emerging as a unique delivery technology, offer a promising avenue for administering medications in various eye conditions. Advancements in pharmaceutical technology have empowered microneedles to facilitate targeted, less invasive, effective, and localized medication administration for ocular diseases. Hollowed, dissolving polymeric, and coated microneedles stand out as specific types tailored for ocular applications. Materials such as borosilicate glass, stainless steel, water-soluble polymers, and engineering plastics find use in manufacturing ocular microneedles. This review aims to provide readers with insights into the potential utilization of microneedles in treating a spectrum of ocular diseases, including retinitis pigmentosa, retinal vascular occlusion, age-related macular degeneration, uveitis, and glaucoma. Microneedles not only enhance visual acuity but also decelerate the progression of several eye conditions. The review discusses both the advantages and drawbacks of ocular microneedles, delving into various types and manufacturing procedures. Furthermore, it emphasizes the applications of ocular microneedles in the medical field, specifically focusing on their delivery methods. The paper concludes by highlighting methods for characterizing ocular microneedles, providing a comprehensive overview of this evolving technology.