A fast plasma-retinal vitamin A equilibrium is consistent with 1) RPE cells and retinal blood vessels of the retina having some of the highest concentrations of RBP-receptors [30,31]; 2) the observation that the first symptom of depleting one’s diet of vitamin A, delayed dark adaptation, can occur within days, despite normal liver stores [32-34]; 3) observations of night-blindness within two weeks of administration of compounds that lower plasma vitamin A [35]; and 4) the observation that injected labeled vitamin A is rapidly incorporated into the neuroretina even in the dark [36]. Here, STRA6 is linked to night blindness.