Glaucoma is a long-term eye condition that can ultimately cause blindness if intraocular pressure (IOP) is not carefully monitored and controlled.

Such monitoring, however, could soon become significantly less complicated. In a study, scientists in Japan have developed a PEDOT:PSS/PVA thin-film-based integrated smart contact lens for real-time, effective intraocular pressure monitoring. The proposed device leverages parity-time symmetry-based wireless technology for ultra-sensitive detection, facilitating early diagnosis and glaucoma treatment.

The current tools for IOP measurement are not portable, convenient, easily accessible, or capable of continuous (24/7) monitoring. These limitations in existing IOP devices have contributed to inadequate ocular health management in glaucoma patients, and this mismanagement could result in severe and irreparable problems for patients.

The lack of proper IOP monitoring is particularly concerning, considering that age is one of the factors behind increased IOP. As the global population grows older, such ocular complications are likely to become more common, especially in Japan, a country that faces one of the world’s most severe population-aging crises. Thus, prompt and proactive efforts to address the current limitations of ocular health monitoring are expected to significantly benefit the nation over time.

In a recent breakthrough, a Japanese research team led by Professor Takeo Miyake from the Graduate School of Information, Production and Systems at Waseda University, and comprised of: Te Xiao, Hanzhe Zhang, Taiki Takamatsu, and Assistant Professor Saman Azhari (all from Waseda University); along with Professor Kazuhiro Kimura and Assistant Professor Atsushige Ashimori (Yamaguchi University); has proposed integrating a thin film into a contact lens to monitor IOP in real time daily. The team’s findings were published in npj Flexible Electronics in January.

In the study, the researchers fabricated a resistive sensor based on a cracked PEDOT:PSS/PVA (PEDOT: Poly(3,4-ethylenedioxythiophene); PSS: Poly(styrenesulfonate); PVA: Polyvinyl alcohol) thin film that leverages a multilayer structure and the intrinsic properties of each layer to readily and effectively measure and monitor the IOP in real time. The team notably combined the sensor with a 70 MHz double-loop gold antenna for high-precision and continuous IOP measurement.

Moreover, by using state-of-the-art parity-time-symmetric wireless technology, the team increased the device’s sensitivity by a factor of 183, compared to conventional wireless sensing systems, making it suitable for daily use by people who require IOP management.

Both in-vitro wireless IOP measurements of a porcine eye and in vivo wireless IOP measurements in rabbit eyes modified through microbead injection—obtained using the fabricated sensor lens—showed a strong linear correlation with corresponding measurements made using a commercial tonometer.

This research demonstrates the way outside-the-box thinking facilitates the use of properties of a well-known material, such as PEDOT:PSS, through a few simple yet innovative steps to tackle a key challenge in ocular health monitoring.

“It is generally very challenging to fabricate a device on a contact lens due to the size limitations while maintaining user comfort. To address these limitations, we used microfabrication to fabricate an IOP sensor that fits well on the contact lens while maintaining flexibility and user comfort,” Miyake said. “Moreover, the use of parity-time symmetry allows for much higher sensitivity in wireless detection, making this work a major step towards the future of daily, real-time ocular health monitoring devices. Overall, our platform is promising for long-term, non-invasive IOP monitoring, thus making a significant contribution to the early diagnosis and treatment of glaucoma.”

Located in Tokyo, Waseda University is a private research institution that has long been dedicated to academic excellence, innovative research, and civic engagement at both the local and global levels since 1882. The university has produced many changemakers in its history, including eight prime ministers and many leaders in business, science and technology, literature, sports, and film. Waseda has strong collaborations with overseas research institutions and is committed to advancing cutting-edge research. 

Reference
Authors: Te Xiao,¹ Hanzhe Zhang,¹ Taiki Takamatsu,¹ Atsushige Ashimori,² Saman Azhari,¹ Kazuhiro Kimura,² and Takeo Miyake.¹

Title of original paper: Ultra-sensitive real-time monitoring of intraocular pressure with an integrated smart contact lens using parity-time symmetry wireless technology

Journal: npj Flexible Electronics        

DOI: 10.1038/s41528-025-00507-3

Affiliations: 1Graduate School of Information, Production and Systems, Waseda University, Japan

2Department of Ophthalmology, Yamaguchi University, Japan