Scientists are working to develop new techniques to administer medication for glaucoma patients that replace the usual regimen of twice-daily eye drops, a sometimes unreliable treatment.
A promising approach, reported in the August issue of Experimental Eye Research, involves a monthly injection of a slow-release drug directly into the eye. The technique, tested on laboratory animals, uses significantly less medication than current treatment and potentially manages the disease better, the researchers said. One injection was comparable to taking eye drops twice a day for 28 days.
Glaucoma, in which eye pressure damages the optic nerve, affects an estimated 2.7 million Americans and puts them at risk for vision loss, according to the National Eye Institute. Treatment usually involves taking eye drops multiple times a day to maintain a healthy eye pressure, but studies have shown as many as 80 percent of patients forget to take the drops, the researchers said. The drops can also leach into the opposite eye, causing retinal hemorrhages and other complications.
A 28-day pilot study at the University of Pittsburgh tested the injection technique on rabbits with normal eye pressure. One group of animals was injected with a biodegradable, spherical-shaped capsule called a microsphere just below the conjunctiva, or thin membrane covering the white part of the eye. The microsphere contained less than three drops of brimonidine tartrate, a glaucoma medication. Another group was injected with blank microspheres and a third received two brimonidine drops a day in the traditional way.
On average, eye pressure dropped 21.4 percent in rabbits injected with the slow-release drug and 19.9 percent in rabbits treated with eye drops. There was no significant change in eye pressure in the animals injected with blank microspheres. The microspheres didn't irritate other eye tissues and had degraded by day 35, the researchers said.