AAV-based gene therapy developments are ongoing worldwide to treat a wide range of inherited retinal diseases since the report of safety and efficacy in phase 1/2 clinical trials of a RPE65 gene augmentation therapy, by subretinal delivery of AAVs carrying the wild-type RPE65 cDNA.2,3,4 A severe limitation of this approach however is the limited packaging capacity (~4.9 Kb) of AAV vectors. The gene discussed is RPE65; the disease is Abnormal retinal morphology.