Hollow Microneedles in Ophthalmology: From Drug Delivery to Integrated Biosensing.

Hollow microneedles are emerging as a promising technology for ocular drug delivery and biosensing, offering a minimally invasive alternative to conventional injection-based therapies. This review addresses current challenges in ocular disease treatment and traces the technological evolution of microneedles, highlighting their ability to precisely access ocular tissues while minimizing patient burden. By penetrating physiological barriers such as the cornea and sclera, microneedle platforms enable localized and controlled drug delivery, thereby addressing key limitations of conventional ophthalmic approaches. Hollow microneedles can be fabricated using various methods, including micromolding and additive manufacturing. Here we focus on silicon-based hollow microneedles enabled by micro- and nanofabrication technologies consisting of lithography and etching steps, which offer high structural precision, reliable fluid transport, and enhanced safety. Recent advances in ocular drug delivery and biosensing demonstrate the potential of hollow microneedles for controlled infusion, localized therapy, and real-time physiological monitoring. Theses developments in corresponding technologies position microneedles as emerging alternatives to eye drops and intravitreal injections, while challenges related to safety, patient compliance, precision control, manufacturing scalability, and regulatory translation are critically examined. Future directions toward smart microneedle platforms and personalized ocular therapies are also outlined, positioning hollow microneedles as a promising interface technology for next-generation ophthalmic drug delivery and biosensing.