Tower microneedle minimizes vitreal reflux in intravitreal injection

Intravitreal injection is widely used for easy control of drug levels in posterior segment of the eye by injecting the drug directly with hypodermic needles. Patients, however, often experience complications from intravitreal injection due to repeated injections, increased intraocular pressure, and infection. In addition, injected drug reflux after intravitreal injection makes it challenging to maintain predetermined drug dose due to the drug loss through backward effusions. Here, we described that the Tower Microneedle can reduce initial reflux and bleb formation due to its smaller outer diameter compared to a traditional hypodermic needle. Furthermore, we use phenylephrine hydrochloride for pupil expansion and demonstrated that Tower Microneedle induced similar pupil expansions using only half the drug volume, in the same period of time, compared to the 31 Gauge hypodermic needle. Consequently, Tower Microneedle achieves the same therapeutic effect in the vitreous body using fewer drugs than a traditional hypodermic needle due to the decreased backward drug effusion. Tower Microneedle described herein holds great promise for intravitreal injection with less reflux and lower drug dosage.