Technology developed in space is being used to create implants which might one day be able to restore some sight to some blind patients.

Scientists at the American space agency, Nasa, say that they are hopeful that human trials will start this year - but are not sure whether the brain will be able to interpret the signals from their hi-tech detector.

Other projects have managed to send low-resolution images back to the brain - some previously sightless patients were able to make out very vague outlines.

However, Nasa says its methods could allow a far more detailed image to be gathered by sensors.

Detailed image

It is using very thin ceramic films which are sensitive to light - each contains approximately 100,000 separate detectors.

This would be capable of producing an image similar to that of the LED display of a digital camera.

The healthy human eye has many millions of cells that convert light into electrical signals, which are then sent along the optic nerve to the brain to be interpreted.

Many people who gradually go blind are suffering from malfunction or the destruction of these rods or cone cells.

Age-related macular degeneration (AMD) is just one condition which affects many thousands of older people in the UK.

In cases where the "sensor" cells at the back of the eye have deteriorated, but the link back to the brain is still intact, using an artificial sensor might be able to help.

Satellite technology

Professor Alex Ignatiev, from the University of Houston, US, told the Nasa website: "In such cases, thin-film ceramic sensors could service as substitutes for bad rods and cones."

Producing the films is a complex task - they are "grown" atom by atom and layer by layer.

The Houston scientists developed the technique on board a satellite launched from the Space Shuttle.

The designers feel that the design will overcome two disadvantages of earlier, silicon-based detectors.

Firstly, silicon is toxic to the human body, whereas ceramic is not, and the large blocks of silicon disrupted the flow of nutrients to the eye - whereas there are gaps between each of the five micron-wide ceramic detectors which allow them to get through.

However, there are still many unknowns - such as whether the brain will learn to interpret the different type of electrical signals sent by the ceramic array.

The researchers suggest that even if it can, it is likely to be a long process for the patient.