Advancements and challenges in ophthalmic microneedles to treat eye diseases

By 2050, more than 61 million people worldwide are expected to lose their vision due to conditions like age-related macular degeneration, glaucoma, diabetic retinopathy, and uveitis (Bourne et al. 2021). This anticipated rise highlights the urgent need for more effective treatment options. While progress continues in developing new pharmacological agents, treating ocular diseases with these therapies remains particularly challenging due to the eye's unique and complex anatomy. This is largely due to the limitations of current drug delivery methods, including systemic administration, topical delivery application, transscleral/periocular drug delivery, and intravitreal injections, which are associated with low bioavailability, side effects, and rapid drug clearance. Given these challenges, microneedles have emerged as a promising alternative. Their minimally invasive nature and ability to precisely target the anterior and posterior segments make them well suited for enhancing therapeutic outcomes while reducing systemic exposure and potential side effects, as well as improving patient adherence (Kang-Mieler et al. 2017; Gadziński et al. 2022). The purpose of this review is to discuss recent advancements, key challenges, and strategies for microneedle-based ocular drug delivery systems, with an emphasis on their potential to treat both anterior and posterior eye diseases.