NIH, National Eye Institute, Bethesda, MD 20892, USA. STRRMD/NIDCD/NIH, Bethesda, MD 20874, USA. Neurophysiology of Vision and Neuropathmology Unit, IRCCS Fondazione G.B. Bietti, Rome 00198, Italy. Department of Ophthalmology, Lund University, Lund, Sweden. Ophthalomology, Soonchunhyang University Bucheon Hospital, Seoul, Korea. Ocular Gene Therapy Core, National Eye Institute, Bethesda, MD 20892, USA. Ophthalomology, Children's Hospital of Philadelphia, Philadelphia, PA, USA. NIH, National Eye Institute, Bethesda, MD 20892, USA. Electronic address: paulsieving@nei.nih.gov.