British-designed "smart glasses" that provide a new set of eyes for the visually impaired are being tested in public for the first time.
The devices, which use a pair of video cameras to enhance residual vision, have the potential to transform the lives of thousands of registered blind people in the UK.
By helping to make the most of existing sight and delivering an all-important sense of depth, they can prevent users colliding with objects such as lamp posts or tripping over kerbs and steps.
The glasses are being trialled by 30 visually impaired volunteers at testing venues in Oxford and Cambridge, where they will navigate through specially constructed obstacle courses.
At the same time a handful of users are giving the devices a "real life" airing in public, mingling with shoppers and tourists in the centre of Oxford.
Dr Stephen Hicks, of the Nuffield Department of Clinical Neurosciences at Oxford University, who led development of the glasses, said:
"The idea of the smart glasses is to give people with poor vision an aid that boosts their awareness of what's around them - allowing greater freedom, independence and confidence to get about, and a much improved quality of life.
"We eventually want to have a product that will look like a regular pair of glasses and cost no more than a few hundred pounds - about the same as a smart phone."
Above: The device consists of a pair of video cameras mounted in a headset, a pocket-sized computer processor, and software that projects images of close-by objects onto displays in the see-through eye pieces.
The software interprets nearby surroundings to make important objects such as kerbs, tables, chairs or groups of people stand out more clearly.
In some cases, details such as facial features can become easier to see, making social interaction more natural. The glasses also work well in low light and can be used to overcome night blindness.
Of the more than 300,000 severely sight impaired people in the UK, it is believed about a third could benefit from the technology.
They include sufferers of sight-loss conditions such as retinitis pigmentosa, diabetic retinopathy, age-related macular degeneration and optic neuropathies.
Many of those affected rely heavily on others to help them get around safely and do simple things such as visiting shops and friends.
More than half of people with seriously impaired vision prefer to stay indoors rather than face the difficulty and danger of walking outside.
Twenty volunteers with a range of eye conditions and levels of vision took part in preliminary tests of an earlier version of the glasses conducted last year by the Oxford team. They quickly adapted to the devices, and those with the poorest vision were found to experience the greatest benefit.
Ian Cairns, 43, a London marketing agency copywriter who was diagnosed with the inherited eye condition choroideremia at the age of 12, tried out the smart glasses in Oxford's Covered Market.
After donning the headset for the first time outside a cafe, he said: "It's.. like the Lord of the Rings when he puts the ring on. And sees things in a new way.. That tablecloth is looking lovely. It's getting the pattern of the tablecloth. It's like I've wandered into an 80s pop video."
Ian, who has an area of central vision left in each eye and started using a cane around three years ago, added: "The glasses could really help with a lot of day-to-day challenges I'm facing in getting around or walking down the street. I do still have some sight.
"What is great about these glasses is that you can see through them and make the most of the vision you've got. They add to what you see with extra information. It's like having a sixth sense, an extra superpower (though it's what most people do every day) - knowing where to look and pick out objects from what's around you. It's very exciting."
Lyn Oliver, 70, from Faringdon in Oxfordshire, who has tried out a number of the scientists' prototypes, said: 'If people are stood outside a shop talking, they often go silent when they see me and watch me walk past. But they've disappeared as far as I am concerned. Have they moved? Have they gone inside the shop? There's a sudden stress about avoiding them.
"The glasses help remove this layer of stress and they do it in a way that is natural to the person using them."
Lyn was diagnosed with retinitis pigmentosa, a progressive eye disease, in her early 20s.
Most of her residual sight is confined to the edges of the visual field, but she can still spot movement.
She recalled how once last year, when unaccompanied by a guide dog and relying on a cane, she walked into a car.
"With the glasses on, I would have seen the car," she said.
The trials are being conducted with support from the Royal National Institute of Blind People (RNIB).