Nutritional Tyrosinemia in animal experiments (Schweizer, Burns a. o.) caused an epithelial corneal dystrophy. The corresponding clinical picture is the Richner-Hanhart-Syndrome with herpetiform epithelial corneal dystrophy, palmo-plantar-keratosis and -- in some case -- a later developing oligophrenia. Goldsmith and coworkers suceeded to find out that all these symptoms are combined with tyrosinemia presumably caused ty one congenital enzyme defect. -- Personal clinical observations of such patients demonstrate that as well the corneal as the dermatological symptoms could be cured by diet, if the diagnosis is made in childhood. Corneal symptoms are still absent with a tyrosinemia as high as 10 mg%. Dietetic formula was found out to maintain this level, which is low enough to avoid the symptoms of Richner-Hanhart-Syndrome and certainly high enough to avoid symptoms of nutritional deficiency. One might expect that oligophrenia will not develop if this diet is used consequently. -- Since the first corneal symptoms develop already during the first years of life the ophthalmologist ought to know this etiology. The levels of tyrosinemia are so exorbitant (30--50 mg%) that the laboratory diagnosis is possible without any difficulty. If the diagnosis is only made in adult patients dietetic therapy is of limited value.