A "revolutionary" device that helps people use sounds to build images in their brain could be used as an alternative to invasive treatment for the blind, scientists say.

The vOICE sensory substitution device trains the brain to turn sounds into images, allowing people to create a picture of the things around them.

Researchers at the University of Bath say The vOICE could be used as an alternative to invasive treatment for blind and partially-sighted people.

A team from the University's Department of Psychology asked blindfolded sighted participants to use the device while taking an eye test.

Results showed the participants - even without any training with the device - were able to achieve the best performance possible.

Dr Michael Proulx, who led the University of Bath team, said: "This level of visual performance exceeds that of the current invasive technique for vision restoration, such as stem cell implants and retinal prostheses after extensive training.

"A recent study found successful vision at a level of 20/800 after the use of stem cells. Although this might improve with time and provide the literal sensation of sight, the affordable and non-invasive nature of The vOICe provides another option.

"Sensory substitution devices are not only an alternative, but might also be best employed in combination with such invasive techniques to train the brain to see again or for the first time."

In the tests, participants were asked to perform a standard eye chart test called the Snellen Tumbling E test, in which the letter E is viewed in different directions and sizes.

Normal, best-corrected visual acuity is considered 20/20, calculated in terms of the distance in feet and the size of the E on the eye chart.

The participants, even without training, were able to achieve the best performance possible, nearly 20/400. This limit appears to be the highest resolution currently possible with the technology.

Dr Peter Meijer, of The Netherlands, who invented The vOICE, Alastair Haigh and Dave Brown of Queen Mary University of London also took part in the research.

'How well do you see what you hear? The acuity of visual-to-auditory sensory substitution' is published in the journal Frontiers in Psychology.