MYO7A and Usher syndrome: Lentiviruses (LVs) are retroviruses with a larger packing capacity (8 kb), which makes them a compelling alternative to AAV vectors for those IRDs whose causative gene coding sequence exceeds the 4.7 kb limit, such as ABCA4-related Stargardt's disease and MYO7A-related Usher's syndrome type 1B.