Contact lenses that change color after releasing drugs into the eye could help doctors determine whether a medication is being delivered to its intended treatment site. (Credit: American Chemical Society)

A drug-delivering contact lens changes color as the medication is 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.