The field of the relation of disturbances of carbohydrate metabolism to cataract was chosen as one fertile for research into the cause of cataract because of the well known frequency of changes in refraction and development of lens opacities in diabetic subjects. Berndt as early as 1834 reported diabetes as a cause of cataract. Duke-Elder differentiated two types of cataract occurring in diabetes: (1) the form of senile cataract appearing frequently and at a relatively early age and (2) a characteristic form peculiar to the disease occurring more rarely. Duke-Elder felt that the diabetic state, by subjecting the lens to an abnormal traffic of fluid, induced the condition and tended to alter its type. He thought that the denaturing action of radiant energy in the presence of excessive sugar and acetone was probably the main factor in the production of cataract in diabetic persons. One must also consider