Researchers at the Terasaki Institute in Los Angeles have developed a prototype of a contact lens that can assist with tear sampling for diagnostic purposes, and to also improve tear flow to potentially prevent dry eye disease. The hydrogel lens contains microchannels through which tears can travel and testing chambers where electrochemical and colorimetric tests can assess sodium levels and pH, respectively.
Tears are a promising source for biomarkers, as they often contain levels of various analytes that are similar to those found in the blood. Examples of clinically relevant indicators found in tears include sodium, which can indicate dry eye disease, and glucose, a marker of diabetes.
Regular collection of tear samples can be a challenge, so one option to assess tears in real-time involves biosensing contact lenses. The newly developed lens contains tiny microchannels that direct tears towards sampling and testing chambers, where an electrochemical test assesses the samples for sodium levels and a simple color change reveals tear pH.
To date, it has been challenging to fabricate microchannels in hydrogel lenses, as the fabrication processes involved have not been suitable for such fine features. The Terasaki researchers achieved this by optimizing the gel so that it was elastic and had a smooth surface, and then used a 3D-printed mold to introduce the microchannels.
During testing, the team noted that if the lens dried out a little, then flow through the channels stopped. However, they realized that when pressure was applied to the lens, such as that applied during blinking, that tear flow would resume.
“In addition to our successful fabrication of microchannels in commercial contact lens hydrogels, we also found that eye-blinking pressure may facilitate tear exchange in the lens through these microchannels,” said Shiming Zhang, a researcher involved in the study. “This is an exciting finding because it opens the possibility for the lenses to be a means of preventing dry eye disease, a condition commonly found in contact lens wearers. We aim to develop a patented contact lens that actively treats this condition by enhancing tear flow in the eye.”
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