Schematic representation of the equine infectious anemia virus (EIAV) vectors used in this study including the titer of each vector in transducing units per ml (TU ml−1). CMVp, the cytomegalovirus immediate/early promoter; Neo, Neomycin open reading frame; bovRho, 0.3 kb fragment from the bovine rhodopsin promoter; LacZ, β-galactosidase reporter gene, ABCR, human ABCR/ABCA4 cDNA; WPRE, modified Woodchuck hepatitis virus post-transcriptional regulatory element.