Russell S, Bennett J, Wellman JA, et al. Efficacy and safety of voretigene neparvovec (AAV2-hRPE65v2) in patients with RPE65-mediated inherited retinal dystrophy: a randomised, controlled, open-label, phase 3 trial. Lancet. 2017;390(10097):849-860. doi:10.1016/S0140-6736(17)31868-8

This trial is the culmination of a long process of bringing a drug to market. It provides a report of a study of patients where 21 were assigned to the therapy and 10 to the control group. Endpoints investigated in this study are intended to support the approval of a gene therapy for a type of genetic blindness called Leber congenital amaurosis type 2 (RPE65-/-). Treatment involved the surgical injection of a recombinant adeno-associated virus (AAV) into the retina between the layer of sensory cells and the layer of pigment cells. Statistical measurements were calibrated to detect improvements in a functional test for vision which amounted to a type of modular obstacle course which could be shuffled and repeated in different light levels. More conventional test for vision were also employed. Safety assessments included general physical and eye exams, lab tests, and self reporting of adverse events. After 1-year of study participants demonstrated improved vision and no serious adverse events.

The gene RPE65 encodes for an enzyme that participates in the visual cycle. The cells in the retina that sense light are called rods and cones. They are made of stacks of membrane proteins which are sensitive to light. Specifically these proteins bind a pigment molecule called

A good overview of the way in which synthetic DNA is delivered into a human is the reference below:

Schultz BR, Chamberlain JS. Recombinant adeno-associated virus transduction and integration. Mol Ther. 2008;16(7):1189-1199. doi:10.1038/mt.2008.103