People with LCA suffer from progressively worse vision due to an abnormality in a gene called RPE65 which prevents the retina from working properly.
At present there are no effective treatments available for LCA.
But doctors at Moorfields Eye Hospital and UCL Institute of Ophthalmology believe the new treatment holds significant potential for future ways of targeting eye disease.
During the trial, the doctors inserted healthy copies of RPE65 into the cells of the retina to help them function normally.
If successful, these cells should restore vision. Previous research using animals found that this gene therapy can bring sight back.
Team leader Professor Robin Ali said: "We have been developing gene therapy for eye disease for almost 15 years but until now we have been evaluating the technology only in the laboratory.
"Testing it for the first time in patients is very important and exciting, and represents a huge step towards establishing gene therapy for the treatment of many different eye conditions."
Whether the human trials have been successful will take "many months" as the people involved will need to be followed-up to assess the long-term effect of the treatment.
But, Professor Ali added, "the results from this first human trial are likely to provide an important basis for many more gene therapy protocols in the future, as well as potentially leading to an effective treatment for a rare but debilitating disease".
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