How Do Drug-Dispensing Contacts Work?
Drug-delivery contacts are normal contacts; they can be corrective for nearsightedness or farsightedness, or they can be without corrective power. To make them into a drug-delivery system, polymer films containing the glaucoma drug are added to the lenses via ultraviolet light polymerization.
Because the centers of the contact lenses are just normal lenses, the wearer can see clearly and the polymer film does not obstruct vision.
After the contact is inserted into the eye, an initial burst of the drug is released. After that, the drug is released into the eye on a regular and consistent basis.
Tests conducted on the aqueous humor (the fluid in the eye) have shown that the dosage of the drug released is appropriate, and that it is comparable to the dosage delivered by conventional eye drops. The lenses can be used to administer the drugs for about a month.
The researchers studied the contacts for use over periods as long as 28 days. During the study, the test subjects did not appear to suffer any complications or side effects from the extended wear. It was noted in about 25 percent of cases that the contact lens did not fit properly and became displaced.
Glaucoma is the second leading cause of blindness worldwide, yet many people with glaucoma fail to take their eye drops as prescribed, even though this can lead to loss of sight. In order to take the difficulty out of dispensing eye medications to treat glaucoma, researchers from the Massachusetts Eye and Ear Infirmary, Harvard Medical School’s Department of Ophthalmology, Boston Children’s Hospital, and the Massachusetts Institute of Technology have devised a type of contact lens that can dispense glaucoma medication.
What Is Glaucoma?
Glaucoma is a disease of the optic nerve, the connection between the retina and the brain that transmits information that we interpret as sight. Glaucoma is often associated with elevated intraocular pressure (the pressure of the fluid inside the eye).
Not everyone with elevated eye pressure develops glaucoma and subsequent eye damage, but having high intraocular pressure increases the risk of developing the disease. In the majority of cases, sustained elevated pressure is believed to damage to the optic nerve, eventually leading to loss of vision.
Often, glaucoma does not cause any symptoms and is not diagnosed until advanced damage to the optic nerve is discovered. Untreated glaucoma can lead to blindness, sometimes as quickly as within a few years. There is no cure for glaucoma, but using eye drops as prescribed can often slow or stop the progression of the disease and save the patient’s vision.
Why Should I Use Drug-Dispensing Contact Lenses?
Many eye conditions are most effectively treated using topically administered eye drops. This mode of treatment is not without its challenges, which can limit its effectiveness in managing disease. One issue is that as little as 5 percent of the drug may actually pass through the cornea and reach the eye.
Another problem is that the eye drops will eventually enter the bloodstream. When certain drugs leave the eye and enter the bloodstream, they can cause various adverse effects.
In addition to these difficulties, many patients do not use their eye drops as prescribed, and this non-compliance can allow the condition to progress. In some cases, especially with elderly patients, a second person may be needed to administer the eye drops on a daily basis.
The use of drug-dispensing contacts instead of eye drops would mean that the patient would only need assistance to insert the contacts about once a month, rather than daily assistance with drops. The constant delivery of certain drugs via a contact lens could overcome some of the difficulties in administering drugs on a consistent basis and in the correct dosage.
Are There Other Options For Me?
The scientists who created the drug-dispensing contact lenses envision other possibilities for it. Since 2010, several other teams have developed contact lenses that can deliver medications, monitor intraocular eye pressure, or measure blood sugar.
All these products are in their very early stages of development, but once these drug-delivery contacts have passed through the clinical trial stages they will be ready for the general public to use.
When Will Drug-Dispensing Contacts Be Available?
The drug-delivery contact lenses have so far been tested only on an animal model. Before drug-delivering contact lenses can be made available on the market for eye doctors to prescribe, they must first go through rigorous clinical trials and be approved by the US Food and Drug Administration.
It may be several years before these lenses are ready to be used by patients with glaucoma or other eye conditions. Until then, the best way to treat glaucoma is still with regular eye drops administered as a doctor has prescribed.