The importance of this transport activity is evident by the finding that over 1200 mutations in the gene encoding ABCA4 are known to cause Stargardt disease (STGD1), an autosomal recessive macular degenerative disease characterized by severe loss in central vision, degeneration of photoreceptors and underlying retinal pigment epithelial cells, and the accumulation of lipofuscin deposits containing di-retinoid compounds10,20. Here, ABCA4 is linked to Stargardt disease.