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Eye implant may reverse blindness
SCIENTISTS have described their first complete design of an implant that will take the place of light-sensitive cells in the retina of a damaged eye.
Current implants use chips that convert light into electrical impulses that are fed to the brain via the optic nerve.
The new device will work differently. It will be placed on a damaged retina and convert light into chemicals that will stimulate nerve cells.
The prototype is being constructed at Stanford University in California.
Dr Stacey Bent of Stanford University calls the device “the holy grail of prostheses”. It takes a new approach to replacing a damaged retina, the layer of cells at the back of the eye that detect light and send signals to the brain.
Trauma or disease can damage or destroy retinal cells. Over the past few years implants have been developed to replace them based on electronic chips that turn light into electrical pulses.
But there are difficulties in placing electronics into the eye.
“The problem with electronic implants is while they are very good it is difficult to make them biocompatible,” said Dr Bent.
“What we a trying to do is a different approach from the current attempts using electrodes to stimulate nerve cells in the eye.”
The new device works chemically rather than electronically.
“Instead of using electrical stimulation from a chip that converts light into electric impulses, we are using an implant that releases neurotransmitters just as the retina does naturally.”
The researchers want light to strike the chip, causing it to release a small amount of neurotransmitter fluid that will stimulate retinal nerve cells.
The implant is to be made of a soft polymer material that will conform to the curvature of the back of the eye.
A key component will be retinal nerve cells that have been persuaded to grow behind the chip so that they can be stimulated effectively.
“We are working on pre-positioning nerve cells in a layer behind the implant,” Dr Bent said. This way they will be in a better position to react to the stimulus from the light sensitive cells above them.
Based on work carried out in the past decade, scientists believe they know how to persuade retinal nerve cells to align.
The back of the implant will be coated with proteins designed to attract filaments that grow out of retinal cells.
It is hoped they will connect the implant to the optic nerve, so that signals can be sent to the brain.
Tests are planned of the device in the laboratory. It will be stimulated with light and the nerve cells monitored to see if they respond. If they are a success, animal tests will follow.
Scientists admire Saturn image
En route to Saturn, the Cassini spacecraft has caught another glimpse of the ringed planet that is growing more detailed with time.
The spectacular image was taken on 9 November when the spacecraft was 111 million kilometres (69 million miles) from the planet.
It shows features in the rings and atmosphere not seen in its last image taken a year ago, as well as five of Saturn’s icy moons.
“After more than a decade of preparation and waiting for arrival, it is satisfying to see the Saturnian moons in this approach picture,” says Dr Gerhard Neukum, of the Free University in Berlin, Germany.
“Soon we will be in orbit around Saturn to investigate these worlds in detail and to decipher their geologic history from close-up images, an exciting prospect.”
Dr Anthony DelGenio, of the US space agency (Nasa), says: “We can only see the general banded structure of Saturn from this distance, but we know that as we get closer those bands will break up before our eyes into smaller features — spots, storms, wave patterns that we’ll be able to see in 10 times more detail than any previous observation of Saturn.
Wesley Huntress, who was director of Nasa’s Solar System Exploration Division in 1990 at the inception of the Cassini mission, remarks: “Wow! So far away, so long to travel, so much effort to make it happen, and so worth it.”
Fourteen camera-team scientists from the United States and Europe will use the two cameras on Cassini to investigate many features of the planet, its moons and its rings.
Cassini will begin a four-year mission in orbit around Saturn when it arrives on 1 July 2004.
It will release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan. The probe could impact in what may be a liquid methane ocean.
China's eyes on the moon
China will send a spacecraft to orbit the moon within three years and plans an unmanned landing in 2010.
The China Daily, quoting senior officials with China's lunar program, said the country's first lunar exploration craft, Chang'e-1, would orbit the moon for at least 12 months.
It is named after an ancient legend about the fairy Chang'e who flies to the moon.
Luan Enjie, director of China's National Space Administration, said he anticipated the orbiting phase would be completed by 2007, followed by the sending of a probe to land on and return from the moon by 2010.
It would collect soil and rock samples, he was quoted as saying.
The orbital module would take three dimensional images of the moon's surface and explore the lunar environment.
"We are following the prescribed order of developing the necessary systems for lunar exploration, such as those for orbiter control and monitoring, data processing as well as the carrier rocket and explorer satellite," said Ouyang Ziyuan, chief scientist of the lunar exploration project.
It made China only the third country in the world to send a man into space. — Dawn ScienceDotcom Report
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