New CL technology to help diagnose and monitor medical conditions may soon be ready for clinical trials. Credit: Pete Kollbaum

An all-printed, stretchable corneal sensor built on commercially available disposable soft contact lenses (CLs), which could supplant electroretinogram (ERG) examinations, has been developed at Purdue University in Indiana, USA.

“This technology will be greatly beneficial to the painless diagnosis or early detection of many ocular diseases, including glaucoma,” said Assistant Professor Chi Hwan Lee, who’s leading the university’s development team.

The corneal sensor is integrated into a soft contact lens via an electrochemical anchoring mechanism to ensure its mechanical and chemical reliability. The resulting device enables the high-fidelity recording of full-field ERG signals in human eyes without the need of topical anaesthesia, said A/Prof Lee.

While commercially available ‘smart’ CL the Sensimed Triggerfish offers continuous and wireless intraocular pressure (IOP) and biomarker (such as glucose) monitoring, its integrated circuit chip is triple the thickness of most soft CLs and more than 75,000 times stiffer, resulting in wearer discomfort and the risk of corneal hypoxia, said researchers. However, the printable sensor developed at Purdue works with standard soft CLs, with biocompatibility softness, near-100% transparency, oxygen transmissibility, wettability and the ability to fit a variety of corneal shapes, they said. The sensor printing method, known as direct-in-writing (DIW), is also well established and should allow for large-scale production, making the technology affordable and disposable, they added.