One of the major drawbacks of topical eyedrops is that it is almost impossible to determine how much of the medication is actually reaching its target. Studies have shown that the percentage is often very low. In an effort to solve that problem, researchers from China Pharmaceutical University and the State Key Laboratory of Bioelectronics, Southeast University, Nanjing, have come up with the idea of a drug-eluting contact lens that changes color as the drug is successfully released into the eye.

The researchers fabricated a color-sensitive contact lens using molecular imprinting, a technique that creates molecular cavities in a polymer structure that match the size and shape of a specific compound, such as a medicine. In laboratory experiments, the molecularly imprinted contact lenses were loaded with timolol, a drug used to treat glaucoma. Then, the team exposed the lenses to a solution of artificial tears, which was used as a stand-in for the eye. As the drug was released from the contacts, the architecture of the molecules near the drug changed, which also changed the color in the iris area of the lenses. No dye was involved in the process, reducing possible side effects. The researchers could see this shift with the naked eye and with a fiber optic spectrometer. They conclude this new lens could control and indicate the sustained release of many ophthalmic drugs.

The study was recently reported in ACS Applied Materials & Interfaces.