Hereditary visual deficiencies can result from isolated or associated alterations of any structure of the eye. The identification of the molecular bases of ophthalmologic disorders has revived interest in several conditions forgotten since their original description. Besides, the deciphering of the molecular bases of these conditions has confirmed preexisting hypothesis on their pathophysiology, but for others, the discovery of the disease gene has added further complexity to the disease process. Two contradictory concepts were particularly highlighted. Several phenotypes described as different clinical entities were brought together by the identification of mutations in the same gene, and conversely, some conditions clinically assigned the same name were proved to be genetically and physiopathologically heterogeneous. In both situations, when established, genotype–phenotype correlations made genetic studies easier and allowed having a better knowledge of the prognosis in infants. Finally, progress during the last 20 years, allow today the development of specific therapeutic approaches.