Researchers at Purdue University have engineered a wireless eye implant that monitors glaucoma by continuously measuring intraocular pressure—a primary risk factor for the disease. The implant could potentially help ophthalmologists catch and treat problematic spikes in pressure that would otherwise go unnoticed.

Glaucoma is the second leading cause of blindness in the world after cataracts. There are no outward symptoms other than perhaps a gradual loss of peripheral vision. The disease is caused by a buildup of intraocular fluid that drains from the pupil through a system of canals. The elevated pressure, if left untreated, can permanently damage the optic nerve, leading to compromised vision and, in some cases, blindness.

If the disease is caught early enough, ophthalmologists can give patients drugs to relieve the pressure and stave off further damage. But regular examinations in a doctor' office are inadequate for charting a glaucoma patient' progress.

“People with glaucoma go to the doctor every six months to check their eye pressure,” says Pedro Irazoqui, an assistant professor of biomedical engineering at Purdue, who is leading the research. “But the problem is that pressure doesn't spike within months: it spikes within hours, sometimes minutes. Once there' a spike, there' a limited amount of time you have to act before it does permanent damage to the optic nerve. We wanted to design a device that monitors pressure continuously, so that if there is a spike, we'd be guaranteed to catch it.”

Toward that end, Irazoqui and his colleagues have designed a tiny microchip, to be implanted between two layers of the eye. The sensor is designed to measure intraocular pressure and wirelessly transmit the data to a nearby computer. A doctor can then access the data and review it for possible warning signs. At present, Irazoqui' team has engineered a prototype of the sensor, although they have yet to test it on animals; that testing is expected to begin by the end of 2007.

One of the major obstacles in creating this type of device is designing a tiny but highly functional chip that uses very little power. Irazoqui' group has overcome this problem in part by designing the sensor to run on nanowatts rather than on microwatts. Such a sensor, once available to patients and doctors, will not only provide better diagnosis for glaucoma, but it may also hold patients accountable for keeping track of their health.

A nanosize wireless sensor (top image, highlighted by the red circle) implanted in the eye will provide 24-hour monitoring of intraocular pressure, a key risk factor for glaucoma. The bottom image shows a prototype of the device. Photo credit: Babak Ziaie, Purdue University.

A nanosize wireless sensor (top image, highlighted by the red circle) implanted in the eye will provide 24-hour monitoring of intraocular pressure, a key risk factor for glaucoma. The bottom image shows a prototype of the device. Photo credit: Babak Ziaie, Purdue University.

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