This study introduced the use of targeted drug delivery to the supraciliary space by using a microneedle and demonstrated dramatic dose sparing of antiglaucoma therapeutic agents compared to topical eye drops. Targeted delivery in this way can increase safety by reducing side effects and could allow a single injection to contain enough drug for long-term sustained delivery.

This study tested the hypothesis that high-density particle-stabilized emulsion droplets (PEDs) can be designed to use gravity to target specific locations in the eye via suprachoroidal space injection. PEDs contained a core of high-density perfluorodecalin measuring ≤35 μm in diameter surrounded and stabilized by fluorescein-tagged, polystyrene nanoparticles that simulated polymeric drug carriers. A hollow microneedle infused PEDs into the suprachoroidal space of rabbit eyes in vivo, which were later dissected and imaged to quantify distribution of fluorescent nanoparticles within the suprachoroidal space. With cornea oriented upward, such that gravity should move PEDs toward the back of the eye, up to 50% of nanoparticles were in the most posterior quadrant near the macula immediately after injection and five days later. With cornea oriented downward, to promote PED movement toward the front of the eye, approximately 60% of injected nanoparticles were targeted to the most anterior quadrant of the posterior segment near ciliary body. Injection of approximately neutral-density particles of the same size showed approximately equal distribution throughout the posterior segment. This study demonstrates for the first time that high-density PEDs can be used to deliver nanoparticles to specific locations in the back of the eye, including targeted delivery to the macula.

This study shows that microneedles can target drug delivery to corneal stroma in a minimally invasive way and demonstrates effective suppression of corneal neovascularization after suture-induced injury using a much lower dose compared with conventional methods.