The SENSIMED Triggerfish® Sensor device developed by SENSIMED AG is a contact lens capable of recording qualitative diurnal IOP profiles over a 24 hour period of normal behavior in patients with suspected IOP fluctuations. Sensimed, a Swiss spin-off from the Swiss Federal Institute of Technology in Lausanne, has launched the very first commercial smart contact lens, designed to improve treatment for people with glaucoma.
In 2008, as a proof of concept, Babak Parviz at the University of Washington in Seattle created a prototype contact lens containing a single red LED. Using the same technology, he has now created a lens capable of monitoring glucose levels in people with diabetes.
It works because glucose levels in tear fluid correspond directly to those found in the blood, making continuous measurement possible without the need for thumb pricks, he says. Parviz’s design calls for the contact lens to send this information wirelessly to a portable device worn by diabetics, allowing them to manage their diet and medication more accurately.
Like an RFID tag or London’s Oyster travel cards, the lens gets its power from a nearby loop antenna – in this case taped to the patient’s face. The powered antenna transmits electricity to the contact lens, which is used to interrogate the sensors, process the signals and transmit the readings back.
Each disposable contact lens is designed to be worn just once for 24 hours, and the patient repeats the process once or twice a year. This allows researchers to look for peaks in eye pressure which vary from patient to patient during the course of a day. This information is then used to schedule the timings of medication.
“The timing of these drugs is important,” Wisner says.
Parviz, however, has taken a different approach. His glucose sensor uses sets of electrodes to run tiny currents through the tear fluid and measures them to detect very small quantities of dissolved sugar. These electrodes, along with a computer chip that contains a radio frequency antenna, are fabricated on a flat substrate made of polyethylene terephthalate (PET), a transparent polymer commonly found in plastic bottles. This is then moulded into the shape of a contact lens to fit the eye.
Parviz plans to use a higher-powered antenna to get a better range, allowing patients to carry a single external device in their breast pocket or on their belt. Preliminary tests show that his sensors can accurately detect even very low glucose levels. Parvis is due to present his results later this month at the IEEE MEMS 2011 conference in Cancún, Mexico.
They have developed both red and blue miniature LEDs – leaving only green for full colour – and have separately built lenses with 3D optics that resemble the head-up visors used to view movies in 3D.
Parviz has yet to combine both the optics and the LEDs in the same contact lens.
Other related technology
DARPA is working on glasses that will endow the user with zoom vision, various forms of nightsight, and act as a heads-up display besides. Perhaps best of all, the proposed kit would also offer “full sphere awareness” – that is, eyes in the back of your head. It is the goals of the DARPA Soldier Centric Imaging via Computational Cameras (SCENICC) project.
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