Leber congenital amaurosis is one of the most serious hereditary retinal diseases and affected children often develop blindness in the first year of life due to photoreceptor-neuron degeneration. The disease usually follows an autosomal recessive mode of inheritance and is with a prevalence of 1:80000 very rare. More than 15 different genes are involved in the genetic heterogeneity and after their analysis about 30% of the investigations remained without findings. Several recent publications report mutations in the gene NMNAT1 in cases of Leber congenital amaurosis. The corresponding enzyme, nicotinamide nucleotide adenylyltranferase 1, is involved in providing metabolic cofactors (NAD) and the enzyme activity is significantly reduced in homozygous or compound heterozygous mutation carriers. Leber congenital amaurosis is the first and only disease to be associated with mutations in the gene NMNAT1. The diagnostic testing of suspected Leber congenital amaurosis is more certain through the molecular genetic analysis of the gene NMNAT1. The diagnostic method is available either as part of a diagnostic panel or as a single analysis.