Stopping blindness: The drug-eluting contact lens
Cover photo credit: John Earle Photography
Growing up, my grandmother’s eyes were always a problem. For years, she was losing her central vision to glaucoma, and numerous surgeries and treatments did not seem to help. Later in life, she could not see my face, but could always tell who I was when I was close.
Glaucoma is the leading cause of irreversible blindness worldwide. While FDA-approved medications such as latanoprost can prevent vision loss by reducing pressure in the eye, their beneficial effects are limited by poor patient compliance: At six months of treatment, compliance is estimated to be only 50 percent.
Why? First, the medications are typically delivered as eye drops, and the drops themselves can cause stinging and burning. The drops also contain preservatives that can cause ocular surface disease.
Perhaps most importantly, latanoprost and other glaucoma drugs halt the disease's progression, but do not reverse it. Taking the drugs does not provide positive feedback that will motivate patients, such as relieving pain.
“Glaucoma is an asymptomatic disease until its end stages,” says Joseph Ciolino, MD, an ophthalmologist at Massachusetts Eye and Ear. “At that point, because of the irreversible nature of the disease, it is too late for treatments to have any effect.”
Ciolino, with Daniel Kohane, MD, PhD, director of the Laboratory for Biomaterials and Drug Delivery at Boston Children’s Hospital, have developed a possible solution to the compliance problem. The two researchers, in collaboration with MIT, have spent several years developing a novel contact lens that dispenses latanoprost and other drugs gradually.
“The basic idea was to make a device that delivers drugs in large quantity for a long period at a relatively constant rate,” says Kohane.
While the idea of a drug-eluting contact lens is not new, the FDA has yet to approve such a device. Past designs have had logistical and dose-release issues. In one design, the lens is dipped or soaked in a drug-containing solution—filling the lens as one would fill a sponge—before being put in the eye. In this design, the absorbed drug is released too quickly.
Kohane and Ciolino were able to overcome this obstacle by pairing two polymers, both FDA-approved for use in the eye. The drug is encapsulated inside the first polymer, PLGA, which is biodegradable and known for its ability to modulate drug release. This PLGA film is then coated with a non-biodegradable polymer gel, pHEMA, and placed on the inside of the contact lens, outside of the central optical area so as to not obscure the patient's vision. The film-to-drug ratio can be modified to adjust the rate of drug release. The lenses could come in a prescription form for patients who are near- or far-sighted, which could help promote compliance.
In a 2009 proof-of-principle paper, Kohane and Ciolino showed that their lens could effectively dispense ciprofloxacin for 30 days and even as long as 100 days. More recently, they published a study demonstrating prolonged delivery of latanoprost to treat glaucoma in rabbits—the first study of its kind to show that a contact lens-based system could release a drug for a full month in an animal model. The lenses delivered the drug at levels comparable to latanoprost drops, and appeared safe in both cultured human cells and in animal studies.
Kohane and Ciolino are now working toward a first-in-human clinical trial. Through an award from the Technology Development Fund, managed by Boston Children’s Technology and Innovation Development Office, the researchers plan to validate the lenses’ efficacy in preclinical glaucoma models, studies that ideally will enable a Phase I trial in the future.
“Our hope is that by decreasing the treatment burden to the patient, we can prevent blindness,” says Ciolino.
Perhaps if my grandmother had had lenses like these, she would have been able to see my face up until she died, at the age of 99.