"Smart" Contact Lenses Detect Real-Time Changes in Pressure, Moisture

Researchers were able to develop a structurally colored contact lens sensor with tunable colors to assist in point-of-care (POC) diagnoses of common eye diseases, according to a study published in the Journal of Materials Chemistry B.

The “smart” contact lenses can show real-time changes in moisture and pressure in eyes by altering colors. The technology can be used to enable early diagnosis of diseases like xerophthalmia and glaucoma and in some cases prevent permanent vision loss. Importantly, the lenses are made from biocompatible hydrogel, “without the addition of any chemical pigments, therefore exhibiting superior biosafety and wearing comfort for wearable applications,” the researchers said.

Specifically, the lenses include “periodic nanostructures within the poly (2-hydroxyethyl methacrylate) (pHEMA) hydrogel matrix,” which, when altered, result in bright, tunable structural colors ranging from red to green to blue, according to a press release.

The researchers emphasize that the structure of the lenses is identical to that of contact lenses already approved by the FDA and used by more than 140 million people worldwide.

Sensitivities to intraocular pressure and eye moisture result from the spacing of periodic nanostructures within the pHEMA hydrogel. When testing the lenses, the researchers noted a linear decrease in the wavelength of the reflectance peak of the lens when pressure changed in the pathological range. With an increase of exerted pressure, the lenses shifted from red to blue in the reflectance spectra.

"Based on these features, the 'smart' contact lens was explored as a means for monitoring xerophthalmia and high intraocular pressure disease. In normal eye-simulation conditions, its color will not change over time; while its color changes from red to blue in the xerophthalmia-simulation condition in about 25 minutes,” said Qilong Zhao, PhD, a lead author of the study.

The researchers hope the development will open a new avenue for instrument-free ophthalmic health monitoring, aiding in eye disease diagnoses and improving personalized medicine for patients.

“The structurally colored contact lens sensor will…inspire the design of a new generation of wearable/implantable medical devices with colorimetric sensing functions via the integration of structurally colored materials, which will contribute to desirable progress in the field of diagnostics,” they said.

Reference

Wang Y, Zhao Q, Du X. Structurally coloured contact lens sensor for point-of-care ophthalmic health monitoring [published online January 17, 2020]. J Mater Chem B. doi: 10.1039/c9tb02389e.