Finally, it is important to note that there are differences between the vector used here (AAV9‐CMV‐human sulfamidase) and the vectors being administered in trials of i.v. and intra‐CSF AAV9‐sulfamidase in children with MPS IIIA, that may affect the degree of retinal transduction and the speed and amount of gene expression. This evidence concerns the gene SGSH and mucopolysaccharidosis type 3A.