Teamwork brings gift of sight

七月 21, 2000

Experts from a range of disciplines have achieved 'the impossible' - an artificial human eye Jennie Brookman reports from Dusseldorf

An artificial human eye that promises to give blind people moderate sight is being developed by a unique interdisciplinary team of German scientists from 15 research institutes.

A retina implant is fitted in the eye of a patient who then wears a pair of spectacles with an integrated mini-camera and transmitter chip, explains project leader Rolf Eckmiller, of Bonn University's division of neuro-infomatics.

The spectacles contain what the scientists call a retina encoder, which replaces the information-processing function of the retina. The implant, called a retina stimulator, is implanted adjacent to the retinal cell layer and has to make contact with a sufficient number of intact cells for electrical stimulation. A wireless signal and energy transmission system provides the communication between implant and encoder.

The encoder maps visual patterns onto impulse sequences for the retina nerve cells via an adaptive dynamic spatial filter. This can be "tuned" to various spatial and temporal receptive field properties of the retina cells during a learning phase that requires a dialogue between the implant-carrying patient and the encoder.

The researchers had to solve two main problems in developing the artificial eye. First, they had to develop a high-tech implant with hundreds of electrodes that is tolerable to the tender retina. The implant is a micro-contact foil, made of ultra-thin layers of polymid and silicon, "as soft as a wet Kleenex", says Eckmiller.

Second, they needed extremely complex and cognitive electronics to send "intelligent information" to the implant and the nerve cells. "The biggest challenge is to build tuneable filters to approximate the information processing of the real retina," says Eckmiller.

Within a couple of years the technology will allow patients to perceive the location and shape of larger objects. "It would be enough to allow blind people to move around without help in a pedestrian zone or in their homes.

This will be a huge leap forward for people suffering from degenerative disorders of the retina such as the inherited retinitis pigmentosa or senile macula degeneration.

Eckmiller said the development was made possible only by bringing together experts from so many different disciplines including opto-electronics, chip design, computer science, biomedical engineering, signal processing, neurophysiology and ophthalmology.

"Until recently it was not considered possible to build an artificial human eye. Only by bringing together a team of such diverse experts has it been possible to reach this level of unbelievable complexity. This is a unique team because it integrates information technology with nano-technology and medical technology. This mix of experts does not exist anywhere else in the world," says Eckmiller.

In future, this technology could potentially be applied to develop spinal implants for paraplegics, for auditory implants and cranial implants to control epilepsy or Parkinson's disease.

But Eckmiller is cautious not to build unrealistic hopes. Asking whether the technology could ever be developed far enough to allow a patient to read a book again, would be "like asking the first people who landed on the moon how long it would be before we build subways there", he says.

The retina implant has already been successfully tested on animals and the tuneability of the retina encoders has been tested on humans with normal vision.

Three years ago, team members set up the company Intelligent Implants GmbH, based in Bonn, which hopes to test the first implant on a human volunteer in 2002 and to launch the implants commercially in 2005.

"Defence of intellectual property is crucial. One has to realise that in economic terms this represents nothing less than a new field equivalent to the size of biotechnology. Neuro-prosthetic devices are part of an emerging field of systems biotechnology," says Eckmiller.

The German government, which has been putting nearly E1.6 million a year (Pounds 1 million) into the project since 1995, is the first in the world to invest in such a risky interdisciplinary project, he says.

"The government was persuaded this is good for people and a chance to create a powerful new industry in which Germany will be in a position to play a trend-setting role."

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