A team of American researchers has developed a contact lens that can deliver a regulated dose of the glaucoma drug latanoprost for up to a month. The lenses encase a thin film of the drug inside the edges of the absorbent plastic used to make contact lenses. They have not yet been tested on human subjects, but appear to be safe in cell culture and animal studies.
The research, entitled In vivo performance of a drug-eluting contact lens to treat glaucoma for a month, is available online and will be published in the January 2014 issue of Biomaterials. Biomaterials is an international journal covering the science and clinical application of biomaterials in cancer diagnosis and therapy, implantable devices, and drug delivery systems.
The authors are Joseph B. Ciolino; Cristina F. Stefanescu; Amy E. Ross; Borja Salvador-Culla; Priscila Cortez; Eden M. Ford; Kate A. Wymbs; Sarah L. Sprague; Daniel R. Mascoop; Shireen S. Rudina; Sunia A. Trauger; Fabiano Cade; and Daniel S. Kohane, who represent the following institutions: Massachusetts Eye and Ear Infirmary; Massachusetts Institute of Technology; Boston Children’s Hospital, Harvard Medical School; and Harvard University.
Definition of Terms
- Drug-eluting: slow, controlled release of a drug
- Biomaterial: synthetic or natural material used in the construction of artificial organs or replacement of bone or tissue
- In vivo: processes taking place in a living organism
- In vitro: processes or reactions taking place in a test tube, culture dish, or elsewhere outside a living organism.
About the Research
From Innovative drug-dispensing contact lens delivers glaucoma medication continuously for a month at MedicalXpress News:
For nearly half a century, contact lenses have been proposed as a means of ocular drug delivery that may someday replace eye drops, but achieving controlled drug release has been a significant challenge. Researchers at Massachusetts Eye and Ear/Harvard Medical School Department of Ophthalmology, Boston Children’s Hospital, and the Massachusetts Institute of Technology are one step closer to an eye drop-free reality with the development of a drug-eluting contact lens designed for prolonged delivery of latanoprost, a common drug used for the treatment of glaucoma, the leading cause of irreversible blindness worldwide.
“In general, eye drops are an inefficient method of drug delivery that has notoriously poor patient adherence. This contact lens design can potentially be used as a treatment for glaucoma and as a platform for other ocular drug delivery applications,” said Joseph Ciolino, M.D, Massachusetts Eye and Ear cornea specialist and lead author of the paper.
The contacts were designed with materials that are FDA-approved for use on the eye. In vivo, single contact lenses were able to achieve, for one month, latanoprost concentrations in the aqueous humor that were comparable to those achieved with daily topical latanoprost solution, the current first-line treatment for glaucoma. The lenses can be made with no refractive power or with the ability to correct the refractive error in nearsighted or farsighted eyes.
About Latanoprost and Prostaglandin Analogues
Prostaglandin is a naturally-occurring blood protein that can lower intraocular pressure, in addition to having many other therapeutic effects. Analogue, or “analogous,” means that the drug is comparable, or similar, to prostaglandin, but has a slightly different chemical composition.
Thus, prostaglandin analogues (PGAs) are drugs that are used in the treatment of open-angle glaucoma or ocular hypertension. At specific dosages, they lower intraocular pressure by increasing the outflow of aqueous humor from the eye. Some of the more common PGAs include travoprost, latanoprost, and bimatoprost.
More about Open-Angle Glaucoma
Glaucoma is a group of eye diseases that damage the optic nerve and is one of the leading causes of vision loss and blindness. Open-angle glaucoma is the most common form of glaucoma.
The eye continuously produces a fluid, called the aqueous (or aqueous humor), that must drain from the eye in order to maintain healthy eye pressure. Aqueous humor is a clear, watery fluid that flows continuously into, and out of, the anterior chamber of the eye, which is the fluid-filled space between the iris and the cornea. It is the aqueous that helps to bring nutrients to the various parts of the eye.
Aqueous fluid drains from the anterior chamber through a filtering meshwork of spongy tissue along the outer edge of the iris (the trabecular meshwork), where the iris and cornea meet, and into a series of tubes, called Schlemm’s canal, that drain the fluid out of the eye. Problems with the flow of aqueous fluid can lead to elevated pressure within the eye.
In primary open-angle glaucoma, the filtering meshwork may become blocked or may drain too slowly. If the aqueous fluid cannot flow out of the eye, or flow out quickly enough, pressure builds inside the eye and can rise to levels that may damage the optic nerve, resulting in vision loss.
More about the Study
Glaucoma is the leading cause of irreversible blindness worldwide. The mainstay of preventive therapy is topical medications (drops) that reduce intraocular pressure (IOP). Unfortunately, only 1–7% of the medication in eye drops is absorbed, and the duration of effect is not sustained.
Eye drops also can be difficult to administer and they can sting, burn, or cause a transient blurring of vision. All of these factors are believed to contribute to the notoriously poor patient adherence with glaucoma therapy, with an estimated adherence rate of less than 50%.
A noninvasive method of sustained ocular drug delivery could help improve adherence to glaucoma therapy by decreasing the frequency of drug administration. Controlling drug release from a contact lens has historically proven to be difficult. Commercially available contact lenses can absorb and release drugs, but the duration of release tends to be limited to only several hours. Recent research has focused on extending the duration of drug release through modification of the contact lens design.
The drug-eluting contact lenses described here could expand the treatment options for glaucoma and other ocular diseases. Given that these contact lenses can release latanoprost for at least four weeks, they could be administered once a month instead of daily administration of latanoprost drops. This simplified treatment regimen could reduce the treatment burden of glaucoma therapy and help address the problem of patient non-adherence.
VisionAware will provide updates of this glaucoma research as they become available.