Macular dystrophy of the cornea is characterized by the formation within the keratocytes of granules containing acid mucopolysaccharides and more particularly keratosulphate. This is followed by the degeneration of the cells with expulsion of the granules, which are then found between the lamellae. These granules are of lysosomal origin. It is probably the keratosulphate catabolic system which is affected, thus explaining the exclusive corneal localization of the disease, since keratosulphate and probably also its catabolizing enzyme are limited to the cornea. It is therefore understandable that other tissues are not affected.