Glaucoma is one of the leading causes of blindness worldwide. A crucial risk factor is elevated intraocular pressure (IOP), which patients should ideally monitor on a daily basis. In practice, this is not always possible: existing measuring instruments are not portable, are not suitable for continuous use and are often only available in clinical settings. As a result, many patients lack the structural insight needed to manage the condition properly.
These limitations become even more problematic in an ageing society. Older age increases the risk of elevated eye pressure, which makes glaucoma more common. Especially in countries such as Japan, where the population is ageing rapidly, there is a growing need for accessible and continuous monitoring of eye health.
Contact lens as a measuring platform
Researchers from Japan have now developed a promising solution: a smart contact lens with an integrated thin-film sensor that can measure eye pressure in real time during daily use. The research is led by Takeo Miyake of the Graduate School of Information, Production and Systems at Waseda University. The results have been published in the scientific journal npj Flexible Electronics.
The researchers integrated an extremely thin, flexible sensor directly into a soft contact lens. This creates a measurement solution that is not only wearable, but also suitable for continuous (24/7) monitoring without compromising the wearer's comfort.
Wireless sensitivity
At the heart of the innovation is a resistive sensor based on a cracked PEDOT:PSS/PVA thin film. By making clever use of a multi-layer structure and the specific material properties of these polymers, the sensor can detect small changes in eye pressure with great accuracy.
For wireless readout, the team combined the sensor with a 70 MHz double gold antenna. In addition, parity-time-symmetric wireless technology was used. This approach increased the sensitivity of the measurements by a factor of 183 compared to conventional wireless sensors. This makes the technology suitable for daily use outside the hospital.
Both laboratory measurements on pig eyes and animal tests on rabbits showed a strong linear correlation between the measurements of the contact lens and those of a commercial tonometer. This indicates a high degree of reliability of the new measurement method.
Non-invasive eye care
According to Miyake, integrating electronics into a contact lens is technically very challenging. ‘It is difficult to add functionality within the limited space of a contact lens without compromising flexibility and wearing comfort,’ he says. By applying microfabrication, the team was able to develop a sensor that fits well into the lens and remains comfortable for the user.
He also emphasises the importance of the chosen wireless technology: ‘Parity-time symmetry enables much higher sensitivity. That brings us a big step closer to daily, real-time monitoring of eye health.’
The researchers see their platform as a promising basis for long-term, non-invasive monitoring of intraocular pressure. This technology could contribute to early diagnosis, better follow-up and, ultimately, more effective treatment of glaucoma. It is an example of how flexible electronics and smart sensor technology can fundamentally change eye care.
Smart lens with night vision
Last year, an international team of neuroscientists and materials scientists developed contact lenses that make near-infrared light visible to humans and animals. The lenses convert invisible infrared light (800–1600 nm) into visible light, without a power source or external equipment. Thanks to nanoparticles in transparent, biocompatible materials, users can combine normal vision with “night vision”, even with their eyes closed.
In tests, mice and human subjects were able to perceive infrared sources and signals, which was confirmed by behavioural and physiological measurements. Colour-coding nanoparticles allow different infrared spectra to be displayed as specific colours. The technology offers prospects for applications in healthcare, communication and security, and possibly also for medical imaging and support for visual impairments.
