Miniature devices treat epilepsy, glaucoma

New miniature devices designed to be implanted in the brain to predict and prevent epileptic seizures and a nanotech sensor for implantation in the eye to treat glaucoma have been developed by researchers at Purdue University, West Lafayette, Ind.

A tiny transmitter three times the width of a human hair can be implanted below the scalp to detect the signs of an epileptic seizure before it occurs. The system records neural signals relayed by electrodes in various points in the brain, indicates Pedro Irazoqui, assistant professor of biomedical engineering. "When epileptics have a seizure, a particular part of the brain starts firing in a way that is abnormal," Irazoqui explains. "Being able to record signals from several parts of the brain at the same time enables you to predict when a seizure is about to start, and then you can take steps to prevent it." Data from the implanted transmitter is picked up by an external receiver.

The most critical aspect of the research is creating a device that transmits a large amount of information at low power. The transmitter consumes 8.8 milliwatts, or about one-third as much power as other implantable transmitters, while transmitting 10 times more information. Another key advantage is that the transmitter has the capacity to collect data specifically related to epileptic seizures from 1,000 channels, or locations, in the brain. While the transmitter and its battery are implanted below the scalp, the electrodes that pick up data are inserted directly in the brain through holes in the skull and then connected to the transmitter by wires.

Another biomedical engineering project involves the development of a sensor that can be implanted in the eye to monitor glaucoma by measuring pressure in the eye's interior. "Glaucoma is one of the big two irreversible, but preventable, causes of blindness," Irazoqui points out.

The disease causes blindness from a buildup of fluid pressure in the interior chamber of the eye, killing fibers in the optic nerve. Glaucoma patients must have their eye pressure checked periodically. If it is high, medication is prescribed or surgery performed. "The problem is that your interocular pressure spikes over hours, sometimes minutes," Irazoqui divulges. "So, you can be fine today and fine in six months and spend three months in the middle where it's very high, killing your optic nerve. What you really need to do is check it often, every couple of minutes, but you can't go to the doctor every couple of minutes for the rest of your life. So, what you need is a device that measures your eye pressure continuously."

The pressure sensor, which is placed between two layers of tissue in the eye, measures the interocular pressure and transmits the information to an external receiver. "This device uses less than a microwatt," Irazoqui marvels. "It uses nanowatts."

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