The UK and US team regenerated dying retinal cells using gene therapy in three patients who had inherited Leber's congenital amaurosis (LCA).
LCA is caused by a faulty version of the RPE65 gene, which leads to destruction of the retina and eventually blindness when people hit their 30s.
Participants walked into walls when navigating a dimly lit maze. Afterwards, 18-year-old Steven Howarth's improved vision helped him navigate the maze quickly.
What is the research?
Three patients with LCA, aged 17, 18 and 23 years, each underwent the experimental procedure in their worst eye.
It took two hours to inject fluid, containing a harmless virus housing a healthy copy of the RPE65 gene, behind the retina.
When properly functioning, RPE65 is expressed in retinal pigment epithelium, producing a protein that regenerates the visual pigment after exposure to light.
Four months after surgery, Steven's retinal function improved so much he was able to see spots of light 25-times less bright as those he could see before. Sensitivity also improved at 37 locations.
When asked to find his way through the maze again, Steven sped through unassisted in 14 seconds. Before surgery, it had taken him 77 seconds.
What do the researchers say?
Lead researcher Professor Robin Ali, from the Institute of Ophthalmology at University College London, said that the results showed 'proof of principle' that gene therapy could treat inherited eye diseases.
'It's important to emphasise that gene therapy is still an experimental treatment not yet generally available to patients,' he said.
'The treatment will be tested in other patients with LCA and we also hope to begin trials for other forms of retinal disease in the future.'
What do other experts say?
Barbara McLaughlan, campaign manager at the Royal National Institute of the Blind, welcomed the news.
'But I am cautious over whether gene therapy can be used to treat other genetic eye conditions, such as age-related macular degeneration, that are influenced by environmental factors as well as genetic ones,' she added.