The most frequent genetic cause of LCA, accounting for up to 15% of all LCA cases in Europe and North-America, is a mutation (c.2991+1655AG) in intron 26 of CEP290. This mutation generates a cryptic splice donor site resulting in the insertion of an aberrant exon (exon X) containing a premature stop codon to CEP290 mRNA. This evidence concerns the gene CEP290 and Leber congenital amaurosis.