According to the World Health Organization, glaucoma is the second leading cause of blindness in the world. While there is no cure for the condition – which sees a build-up of pressure in the eyeball that damages the optic nerve – eye drops can help alleviate symptoms and stall the onset of vision loss. However, patients don't always comply with the dosing recommendations. New contact lenses impregnated with medication could solve this problem and improve patient outcomes.

A team of American scientists first developed the lenses in 2014 using a medication encapsulated in a thin polymer film. Unlike drug-delivering contact lenses that had come before, the new lenses were able to deliver medication slowly over time – taking up to a month to release their cargo. Now, in a study published online today in the journal Ophthalmology, the researchers have shown that the lenses are equally effective as eye drops in reducing eye pressure in glaucoma patients – at least those of the simian variety.

The benefit of the lenses over eyedrops comes from a compliance issue. Because the eyedrops of a medication known as latanoprost can cause stinging and burning and simply be difficult to administer, some studies have shown that up to 50 percent of patients fail to comply with the dosage requirements. A lens on the other hand, once placed in the eye, would deliver medicine as intended with very little work on the patient's part.

"If we can address the problem of compliance, we may help patients adhere to the therapy necessary to maintain vision in diseases like glaucoma, saving millions from preventable blindness," said Dr. Joseph B. Ciolino. "This study also raises the possibility that we may have an option for glaucoma that's more effective than what we have today."

The medication is embedded in a ring around the lens, which allows the center to remain clear. The film can be applied to lenses that correct either nearsightedness or farsightedness, and the lenses in the study only needed to be changed once per week.

In developing the lenses, the researchers tested them out on four monkeys that had glaucoma. They tested two versions of the lenses – one with a low dose of medication and one with a higher dose. The low-dose lenses were as effective as drops in relieving pressure, while the higher-dose lenses worked even better, although the researchers say more work is needed to confirm the higher-dose results.

The lens developers are now designing clinical trials to see how well the contacts will work in humans, and sort out any safety issues that may arise.