The non-depolymerised mucopolysaccharides of the anterior chamber angle can become hydrated. This biological oedema can obstruct the trabeculae, but the physiological liberation of catabolic enzymes from the lysosomes depolymerises the mucopolysaccharides and prevents this obstruction. This is, on the contrary, facilitated by the corticosteroids, which reinforce the lysosomal membranes and impede the liberation of the catabolic enzymes. There are clones of goniocytes which are corticosensitive and others which are not. Depending upon the predominance of one or the other, the cortisone test will be positive or negative. The outflow facility of the aqueous humour is determined by the hydration state of the trabeculae. This state depends upon the polymerisation of the mucopolysaccharides of the trabecular skeleton.