Wireless soft contact lens sensor shows promise for minimally invasive, continuous IOP measurement

Swiss researchers are collaborating to develop a wireless soft contact lens sensor that could be used for minimally invasive continuous monitoring of IOP fluctuation and ocular pulsation.

Elie N. Pitchon, MD, MSc, described the progress achieved so far with this project, which represents efforts of investigators from the Jules Gonin Eye Hospital, Lausanne, the Swiss Federal Institute of Technology, Lausanne, and Sensimed AG.

The principle for measurement with the device is based on detection of the tiny changes in corneoscleral curvature that occur with changing IOP. The measurement sensor is a strain gauge embedded in a disposable soft silicone contact lens. There is a wireless telemetric connection from the contact lens sensor to an external antenna, which is in turn connected to a portable data recorder. The collected data are downloaded to a computer for analysis.

Initial studies in pig eyes showed that the signal from the strain gauges of the contact lens sensor correlated highly to IOP changes in ex vivo cannulated pig eyes over a studied range of up to 30 mm Hg. Testing in humans during the recovery phase after oculopression-induced IOP elevation showed a correlation between the contact lens sensor signal and IOP measurements obtained with Goldmann tonometry. In addition, ocular pulse amplitude measured with the contact lens sensor correlated to measurements obtained from dynamic contour tonometry and of cardiac pulsation frequency.

"So far the device has demonstrated an excellent and robust wireless connection with the rest of the system and the comfort of the sensor was good, although the wearing time was only about 2 hours," Dr. Pitchon said. "However, these are our first, in vivo clinical results. Now we are continuing investigations with the hope that the contact lens sensor will become useful for monitoring IOP changes over 24 hours."