It can sometimes be challenging for ophthalmologists, making definitive on-the-spot diagnoses of eye problems. A new "smart" contact lens is designed to help, however, by changing color in response to two common disorders.
Developed by a team from the Shenzhen Institutes of Advanced Technology (SIAT) at the Chinese Academy of Sciences, the prototype lens is made of a biocompatible hydrogel. That gel is in turn composed of a polymer known as poly(2-hydroxyethyl methacrylate), or pHEMA for short. No additional chemical pigments are used.
Ordinarily, the pHEMA appears to be red. Within about 25 minutes of being placed on an eye that's abnormally dry, though, the polymer's nanostructure changes in reaction to the low moisture levels. As a result, it switches to reflecting incoming light as being blue.
The smart contact is reportedly also capable of detecting conditions such as glaucoma, in which the eye's intraocular pressure is dangerously high. In that case, the pressure on the hydrogel once again alters its reflective nanostructure, this time causing it to appear green.
"This study provides a novel and smart wearable device for timely and facile warning of the risks of xerophthalmia [dry eye] and high intraocular pressure disease," says the lead scientist, Prof. Prof. Du Xuemin. "It will also inspire the design of a new generation of wearable devices with colorimetric sensing capabilities for real-time POC [point-of-care] monitoring of various human body signs and diseases."
It should be noted that this isn't the first color-changing therapeutic contact lens we've seen. Previous examples have included one that turns blue to indicate that it has successfully delivered medication into the eye, and another that alerts diabetics to changes in their blood glucose levels.
A paper on the SIAT research was recently published in the Journal of Materials Chemistry B.
Source: Chinese Academy of Sciences
