Nucleic acids and viral vectors, particularly adeno-associated virus (AAV) vectors are provided that encode Cas9 and paired guide RNAs. The nucleic acids and vectors, and compositions that comprise them, can be used in methods to treat subjects, to alter cells in subjects who may suffer from an inherited retinal dystrophy such as CEP290 associated disease or who may be in need of alteration of a cell or a cellular nucleic acid sequence associated with an inherited retinal dystrophy such as the CEP290 gene, and/or to treat inherited retinal dystrophies including CEP290 associated disease.