BEST1 and Best vitelliform macular dystrophy: Best1 is a transmembrane protein with molecular weight of ∼68 kDa [5,6] and is thought to be an ion channel: it was shown to be permeable for chloride, thiocyanate, bicarbonate, glutamate and GABA.[4,7–10] The exact structure and functions of the protein and the pathogenesis of BVMD are still under discussion.