Among these 22 patients clinically diagnosed with BCD, four had previously undergone genetic testing from a prospective study (Genetic study in hereditary retinal and optic nerve diseases, IRB 201601569B0C601), all of whom were confirmed to have the homozygous mutation c.802–8_810del17insGC in CYP4V2 gene (Fig. 1), which is the most common pathogenic variant of BCD in Eastern countries [12, 13]. Here, CYP4V2 is linked to Bietti crystalline dystrophy.