ABCA4 and severe early-childhood-onset retinal dystrophy: It is now generally believed that mutations in ABCA4 result in a spectrum of related retinal dystrophies, including STGD, bull’s eye maculopathy [41], [42], retinitis pigmentosa [43], [44], [45], [46], [47], cone rod dystrophy and age-related macular degeneration [48].