Minimally invasive microneedles for ocular drug delivery

ABSTRACT

Introduction: Anterior and posterior segment eye diseases are highly challenging to treat, due to the barrier properties and relative inaccessibility of the ocular tissues. Topical eye drops and systemically delivered treatments result in low bioavailability. Alternatively, direct injection of medication into the ocular tissues is clinically employed to overcome the barrier properties, but injections cause significant tissue damage and are associated with a number of untoward side effects and poor patient compliance. Microneedles (MNs) has been recently introduced as a minimally invasive means for localizing drug formulation within the target ocular tissues with greater precision and accuracy than the hypodermic needles.

Areas covered: This review article seeks to provide an overview of a range of challenges that are often faced to achieve efficient ocular drug levels within targeted tissue(s) of the eye. It also describes the problems encountered using conventional hypodermic needle-based ocular injections for anterior and posterior segment drug delivery. It discusses research carried out in the field of MNs, to date.

Expert opinion: MNs can aid in localization of drug delivery systems within the selected ocular tissue. And, hold the potential to revolutionize the way drug formulations are administered to the eye. However, the current limitations and challenges of MNs application warrant further research in this field to enable its widespread clinical application.

KEYWORDS:

• Ocular drug delivery
• posterior segment
• anterior segment
• microneedle
• minimally-invasive

Article highlights

• Visual impairment and blindness are potentially the most devastating health problem worldwide.

• Drug delivery to the eye is challenging due to the extremely delicate nature, relative inaccessibility, and barrier properties of ocular tissues

• Topical and systemic routes of ocular drug delivery result in low or sub-therapeutic drug levels; drug delivery implants need surgical implantation.

• Injections into the eye using conventional hypodermic can provide direct access to the target tissues. However, this method is highly invasive and causes considerable discomfort, pain and associated with a number of side effects

• Microneedles (MNs) could offer minimally-invasive means of ocular drug delivery, less tissue trauma, less drug dosage and precise localisation of the medication.

• MNs allow precise injections within the thin ocular tissues (e.g. sclera and cornea) – an advantage for localized drug delivery

• MNs when integrated with sustain drug delivery formulations can offer long-term localised drug delivery in treating both anterior and posterior segment eye diseases. This box summarizes key points contained in the article.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

This paper was not funded.