Solar-Powered Eye Sensor

A cornea-implanted computer can monitor the eyeball's pressure

In the future, that twinkle in your loved one's eye might be an implanted solar-powered pressure monitor. At the 2011 IEEE International Solid-State Circuits Conference in February, engineers from the University of Michigan, in Ann Arbor, described their work on a cubic-millimeter-size sensor meant to monitor pressure inside the eye. The researchers have yet to test the device in human eyes or animal ones, but they hope their system will one day thwart optic nerve damage brought on by glaucoma.

To determine a glaucoma patient's treatment, doctors must monitor pressure inside the eye, says Gregory Chen, a graduate student of electrical engineering at Michigan. Today's methods gauge that pressure by pushing on the cornea, the eye's clear outer coating. The results may be inaccurate: "If you just happen to have a really thick cornea, your eye is going to be harder, no matter what the pressure is," Chen says. The engineers' prototype device would allow a microelectromechanical systems (MEMS) capacitive sensor to record pressure from inside the eye about every 15 minutes and store it to static RAM. Once a day, the system would wirelessly transmit the day's data, via two on-chip inductors, to a wand. The inductors would send the data at both 400- and 900-megahertz carrier frequencies, as a means of mitigating the signal's noise and increasing its range.