Ocular Drug Delivery: Present Innovations and Future Challenges

Abstract

Ocular drug delivery has always been a challenge for ophthalmologists and drug-delivery scientists due to the presence of various anatomic and physiologic barriers. Inimitable static and dynamic ocular barriers not only exclude the entry of xenobiotics but also discourage the active absorption of therapeutic agents. Designing an ideal delivery scheme should include enhanced drug bioavailability and controlled release of drug at the site of action, which can overcome various ocular barriers. Conventional ophthalmic medications include the use of topical eye drops and intravitreal injections of anti-vascular endothelial growth factor agent for treatment of anterior and posterior segment disorders, respectively. Current inventions for anterior ocular segment disorders such as punctum plugs, ocular implants, drug-eluting contact lenses, and ocular iontophoresis represent state-of-the-art inventions for sustained and controlled drug release. Parallel efforts for ocular drug delivery technologies for back of the eye disorders have resulted in the approval of various intravitreal implants. Novel drug-delivery technologies, including nanoparticles, nanomicelles, dendrimers, microneedles, liposomes, and nanowafers, are increasingly studied for anterior and posterior disorders. To achieve patient compliance for back of the eye disorders, novel approaches for noninvasive delivery of potent therapeutic agents are on the rise. In this review article, we discuss past successes, present inventions, and future challenges in ocular drug-delivery technologies. This expert opinion also discusses the future challenges for ocular drug-delivery systems and the clinical translatable potential of nanotechnology from benchtop to bedside.

Advances in chemistry and composition of soft materials for drug releasing contact lenses

“…As eyes have both static and dynamic barriers including static barriers of corneal layers, blood aqueous barrier and dynamic barriers of retinal blood and conjunctival barrier, it causes inhibition to the uptake of drug and thereby reducing the bioavailability. 6,7 Different routes of administration exist to treat ocular diseases (Fig. 1).…”

“…All these routes also suffer from the similar obstacles. 6 There are some transporters present in the eye which are known to efflux drug molecules outside and reduce bioavailability of the drug. 8,9 Due to difference in morphologies and barrier properties of the anterior and posterior segments in eye, different therapeutic measures have to be devised to ensure successful therapy.…”

Cerium Oxide Nanoparticles (Nanoceria): Hopes in Soft Tissue Engineering

“…The long-term safety of nanoceria in ophthalmic tissue was documented, as it had no negative influences on the function or cytoarchitecture of rat retinas [ 141 ]. Due to its nano-scaled diameters, the topical treatment of nanoceria could be attained via corneal permeation through PEGylation and liposomal encapsulation strategies, with no changes in the physicochemical properties of nanoceria, making it a potent candidate for treating several eye disorders in the posterior segment [ 142 ].…”

<p>Comparative Assessment of Distribution Characteristics and Ocular Pharmacokinetics of Norvancomycin Between Continuous Topical Ocular Instillation and Hourly Administration of Eye Drop</p>

“…9 Various methods, such as punctum plugs, drugeluting contact lenses, ocular implants, and nanocarrier systems, have been explored to prolong the pre-corneal time and improve the drug concentration in the ocular tissues for treating anterior ocular segment diseases. [10][11][12] However, limiting factors of these methods are biodegradation, an inability to precisely control drug delivery, and idiopathic harm to the eyeball. 7,[13][14][15] The continuous topical ocular instillation drug delivery (CTOIDD) system in our study consists of a cribriform polyvinyl chloride tube with a ring shape and an attached drug pump ( Figure 1A).…”