Crystallizing Vision by Microneedles: A Systematic Review

The World Health Organization (WHO) reports that around 196 million people are affected by age-related macular degeneration (AMD), while 146 million suffer from diabetic retinopathy. Treating these conditions presents significant clinical challenges due to ocular barriers and mechanisms like blinking and drainage, which hinder effective drug delivery. Although topical treatments such as eye drops, gels, and ointments are commonly used for anterior segment diseases, their effectiveness is limited, with less than 5% bioavailability due to rapid drainage. Drug targeting can be improved by employing direct injections. Intravitreal injections (IVT) are generally painless, but they can lead to complications like retinal inflammation and poor patient compliance, while retrobulbar injections pose risks such as retinal detachment and hemorrhage. Additionally, traditional drug delivery systems struggle with limited intraocular penetration and quick ocular clearance. Microneedles (MN), which are small patches with micron-scale needles (less than 1 mm), offer a promising alternative for localized drug delivery. They offer increased penetration of drugs. These microneedles improve precision and accuracy in targeting ocular tissues and are less reliant on the physicochemical properties of drugs. This innovative delivery method not only reduces tissue damage compared to conventional hypodermic needles (over 10 mm long) but also allows for more effective treatment of various anterior and posterior eye diseases. This review paper describes the necessity of microneedles in ocular drug delivery, as well as the various types of microneedles, highlighting their respective advantages and disadvantages. This paper will also discuss in detail about dissolving MNs and a summary of other MN types. By exploring this emerging technology, we can improve therapeutic outcomes for patients with debilitating eye conditions.