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Researchers have developed a contact lens that changes color as eye drop and eye ointment drugs are release into the eye. The visual indicator could help eye doctors and patients determine whether these medications are where they should be.
Studies suggest that less than 5 percent of drugs in eye drops and ointments are absorbed, and much of the absorbed medication ends up in the bloodstream instead of the eye, causing side effects. Contact lenses may be a more effective way to deliver drugs directly to the eye, but real-time monitoring of drug release is still a challenge.
Dawei Deng and Zhouying Xie 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.
They 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. The new lens could control and indicate the sustained release of many ophthalmic drugs.