One of the most common causes of LCA is a mutation in the RPE65 gene, which is also prevalent in a strain of dogs called Briards. The gene codes for an essential protein for vision.
However, the disease does not affect all of the photoreceptors, the light sensing cells, so the eye still has the capacity to detect light. Scientists took advantage of the healthy photoreceptors in Briard dogs and injected a virus carrying copies of the normal RPE65 gene. This virus was chosen because it did not make people or dogs sick.