Most cases of night-blindness (nyctalopia or hemeralopia) do occur without an apparent organic eye-disease. In the past one spoke of essential or epidemic night-blindness. It is caused by a vitamin deficiency, and is a result of failing dark adaptation; it may lead to xerophthalmia, and finally to a complete permanent blindness, if not treated in time with vitamin A or vitamin A containing food (butter, egg-yolk, fish-liver oil). From time immemorial the healing effects of the intake of liver from fish and various animals for night-blindness has been reported from countries all over the world. In medical literature it has been recommended in the Papyrus Ebers (ca. 1500 B.C.), by the old Greek writers, from Hippocrates to Galen, and later to Oribasius and others. In the early sixteenth century Jac. Bontius (1592-1631) learned this therapy from empiric folk-medicine and advocated shark-liver as a specific medicine. Notwithstanding scattered reports of the dramatic favourable result of liver-treatment in patients with night-blindness, it would last until experimental research with a fat-poor diet led to the discovery (1913) and identification of vitamin A in our century, and the high vitamin A content of liver was established. Thus recognizing the value of the old liver-treatment, finally vitamin A was introduced in official ophthalmology. So an age-old, nearly universal favourable experience of empiric medicine had been neglected to the detriment of countless sufferers of night-blindness. Today systematic administration in cases of impending blindness, especially in some Asiatic areas, has already prevented the development of lasting blindness on a large scale.