BEST1, the gene encoding bestrophin-1, was first identified associated with Best disease, an early onset autosomal dominant macular dystrophy characterised by an abnormal electrooculargram (EOG) and vitelliform lesions in the macula (Petrukin etal. 1998 and Marquardt et al. 1998). Since its discovery over 100, mostly missense, mutations in BEST1 have been associated with Best disease. A second dominant retinal dystrophy is caused by mutations in BEST1 (Yardley et al 2004). Autosomal dominant vitreoretinochoroidopahty (ADVIRC) is characterised by a hyperpigmented band around the periphery of the retina and punctate retinal and vitreous opacities.