Electroretinography (ERG) is a valuable tool for diagnosing and studying ocular diseases, as it involves measuring the electric potential in the retina. Traditionally, multi-electrode systems for ERG have been uncomfortable and built on top of hard contact lenses. Researchers have developed a new multi-electrode ERG system that is built on top of soft contact lenses, aiming to address this issue. This innovative system has demonstrated excellent performance and biocompatibility, and it is expected to expand the possibilities of what can be achieved with ERG. Eye diseases are on the rise globally, largely due to the aging population.It is essential to improve our diagnostic techniques for the early detection and monitoring of ocular diseases, not only due to the aging population but also because of the increased screen time compared to previous generations. Our use of displays will most likely continue to rise with technologies such as virtual and augmented reality.
One of the tools ophthalmologists have at their disposal is electroretinography (ERG), which still has untapped potential. In simple terms, ERG involves measuring the electrical potentials generated by neurons and other cells in the retina from the surface of the cornea. Many ocular diseases can be diagnosed and monitored through this method.Diseases like glaucoma, retinitis pigmentosa, and diabetic retinopathy can cause abnormalities in a person’s ERG signals. While there are various types of ERG measurement devices available, only a few electrodes can measure localized ERG signals from different areas of the retina simultaneously. Typically, electrodes are placed on hard contact lenses for these measurements, which makes the process more complicated, expensive, and uncomfortable for the patient.
To address these challenges, Professor Takeo Miyake and his research team from the Graduate School of Information, Production and Systems at Waseda University took on the task.Japan aimed to develop a new soft ERG multi-electrode system to address existing issues. Their latest study, featured in Advanced Materials Technologies on May 7, 2024, outlines their discoveries. Saman Azhari from the Graduate School of Information, Production and Systems at Waseda University, along with Atsushige Ashimori and Kazuhiro Kimura from the Department of Ophthalmology at Yamaguchi University, co-authored the study.
The proposed system incorporates a commercially available soft disposable contact lens. The researchers began by immersing this contact lens in a solution containing the monomer 3,4-ethylenedioxythiophene.The researchers carefully placed gold mesh electrodes and connecting wires onto the inner surface of the contact lens using a solution containing EDOT. When a current was circulated through the solution, the EDOT formed a polymer called PEDOT, which effectively adhered to the contact lens and secured the gold components in place.
One of the main benefits of this method is that the PEDOT layer can be overoxidized using a DC voltage in dry conditions, creating a highly insulating layer on the connecting wire. This insulation is crucial for preventing interference between different retinal signals flowing through the gold wires.
The researchers have developed a multi-electrode system for ERG measurements that is flexible, highly transparent, and comfortable. This system allows for signals to be transmitted between the electrodes without overoxidizing, ensuring good electrical contact with the eye. Through careful design of the gold mesh and encapsulation with PEDOT, the system spreads currents and maintains its functionality.
In order to test the optoelectrical properties of the multi-electrodes, the researchers conducted experiments on rabbits. The result of their innovative process is a system that is as comfortable as commercial disposable contact lenses. Miyake comments that the system has been carefully examined and shows promising results.The biocompatibility of ice was confirmed in animal experiments, indicating a potential correlation between electrode placement and the strength of recorded ERG signals. In simpler terms, our design could allow for accurate spatial measurements of multiple ERG signals at the same time.
Overall, the results of this study could improve our understanding and diagnosis of eye diseases. According to Miyake, “The use of augmented and virtual reality devices is rapidly increasing, and the accurate and ongoing monitoring of eye conditions will soon be essential.” A smart contact lens like the one created in this study could be the solution.The study found that using multi-electrode electroretinography with transparent microelectrodes printed on a soft and wet contact lens can help monitor the health of the eyes in real time. This technology allows for the data to be transmitted to a healthcare professional while the user goes about their daily routine, potentially preventing irreparable damage to the eyes.
