Drug-eluting contact lenses have been discussed as a potential treatment modality for decades but have yet to reach patients. To those researching and developing this novel drug delivery method, the lenses continue to represent a possibility of more efficient treatment for a multitude of ocular issues.
Alex Hui, OD, a PhD candidate at the Centre for Contact Lens Research, University of Waterloo, told Primary Care Optometry News that nearly every type of ocular drug has been evaluated for contact lens delivery.
“In addition to studies of antibiotics and glaucoma, drugs for dry eye or ocular surface disease (cyclosporine A), anti-inflammatory drugs (dexamethasone, prednisolone), nonsteroidal anti-inflammatory drugs (ketorolac) and anti-allergy drugs (ketotifen) have all been investigated,” he said.
Establishing a need
While the current gold standard for ocular drug delivery – topical eye drops – has been well adopted by ophthalmic practitioners, it also suffers from critical shortcomings that can limit its therapeutic efficacy. Utilization of contact lenses as a delivery method could fill a need that currently exists in treating ocular disease with topical pharmaceuticals.
“At present, topical eye drops remain the most common method for treating ocular disease, accounting for 90% of ophthalmic formulations, and they are readily accepted by patients due to their convenience and cost effectiveness,” Phan and colleagues wrote in a Clinical & Experimental Pharmacology report. “However, the ocular anatomy presents several barriers that prevent the effective and efficient delivery of medication from eye drops, including continuous tear dilution, dispersion and drainage during blinking and tear flow, nonspecific absorption and variable drug penetration. This results in only 1% to 7% of the medication within an eye drop reaching the target tissue and exerting a therapeutic effect.”
Lyndon Jones, BSc, PhD, FCOptom, DipCLP, DipOrth, FAAO, FIACLE, professor at the University of Waterloo and director of the Centre for Contact Lens Research, echoed this sentiment and lauded the use of contact lenses as a potentially superior delivery system.
“Data shows that less than 5% of the active drug in an eye drop actually reaches its target, due to poor administration techniques, tear clearance and poor adsorption,” he told PCON. “Contact lenses will be able to deliver therapeutic agents from periods ranging from days to several weeks, and the delivery to the target tissue will be much more effective.”
“With a contact lens, the contacts are placed right on the cornea, so the drug in the contact lens has to go to the cornea because it has nowhere else to go,” Anuj Chauhan, PhD, professor and researcher at the University of Florida, said in an interview. “There’s a significant increase in bioavailability when you deliver drugs by contact lenses.”
Phan and colleagues noted in their study that using contact lenses could translate to an efficiency 35 times greater than that of conventional eye drops.
“Over 50% of the drugs released from a contact lens can diffuse into the cornea,” they reported. “This increase in efficiency permits substantially reduced concentrations to be used, decreasing the potential for side effects, as less drug is absorbed systemically.”
Many researchers such as Chauhan, Daniel S. Kohane, MD, PhD, professor at Harvard Medical School and director of the Laboratory for Biomaterials Drug Delivery at Boston’s Children Hospital, and Joseph B. Ciolino, MD, assistant professor of ophthalmology at Harvard Medical School and a clinician scientist at Massachusetts Eye and Ear, have focused on treating glaucoma with drug-eluting contacts.
Hui and colleagues are studying molecular imprinting to extend drug release from contact
lenses. These lenses are embedded with ciprofloxacin, causing a yellow tinge.
Image: Muntz A