ABCA4 and Cone rod dystrophy: For the study of ABCA4 gene the following techniques were used: a) Genotyping APEX (Arrayed Primer Extension) for ABCA4 gene (Asper biotech, Tartu, Estonia, http://www.asperbio.com/asper-ophthalmics/stargardt-disease-cone-rod-dystrophy-abca4/stargardt-disease-targeted-mutation-analysis); b) Sanger sequencing of all the coding exons and intronic flanking sequences, and c) MLPA (Multiplex Ligation-dependent Probe Amplification) analysis using a commercial kit (SALSA® MLPA® P151-P152 ABCA4 probemix, MRC-Holland, Amsterdam, the Netherland) to study ABCA4 exonic deletions or duplications.