Color-changing contact lens senses eye pressure and moisture for POC eye-health monitoring

March 10, 2020
A pigment-free polymer contact lens contains optical nanostructures that change period (and thus color) based on eye moisture and pressure.

A research group led by Du Xuemin from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences (Beijing, China) has developed a "smart" contact lens that can show real-time changes in moisture and pressure by altering its color based on the changing periodicity of an optical nanostructure.1 The "smart" contact lens can potentially be used for point-of-care (POC) diagnosis of xerophthalmia and high-intraocular-pressure disease.

Early diagnosis is important for avoiding severe eye problems, such as exophthalmia (which causes relatively mild symptoms) or glaucoma (which may lead to loss of vision). Such diagnoses rely on monitoring of several features with significant pathologic relevance, such as the amount of tears and intraocular pressure. However, current methods usually require complex procedures and instruments operated by professionals, causing difficulties for point-of-care (POC) ophthalmic health monitoring.

The "smart" contact lens features periodic nanostructures within the poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel matrix, resulting in bright, tunable structural colors ranging from red to green to blue (see figure).

Pigment-free

This structurally colored contact lens sensor is made solely from a biocompatible hydrogel without the addition of any chemical pigments. Importantly, the spacing of periodic nanostructures within the pHEMA hydrogel is sensitive to changes in moisture and pressure, leading to real-time color changes in the contact lens.

"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 Zhao Qilong, first author of the study.

Additionally, a linear decrease in the wavelength of the reflectance peak of the "smart"  contact lens is observed when human intraocular pressure changes in the pathological range.

Source: http://english.cas.cn/newsroom/research_news/tech/202002/t20200217_229968.shtml

REFERENCE:

1. Yunlong Wang et al., Journal of Materials Chemistry B (2020); https://doi.org/10.1039/C9TB02389E.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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