[Biological parameters of so-called "senile cataracts"]

With advancing age the weight of the lens of the eye tends to increase in both human beings and animals; simultaneously, the percentage of enzymes in the entire lens decreases. These phenomena can be explained by the fact that the enzymes are mostly located in the epithelium and superficial nucleate fibers of the lens. In addition, the central part of the lens, which steadily increases its volume and percentage of the weight of the whole lens over a lifetime, has relatively few or no enzymes at all. In the superficial layers the enzyme content adenosine triphosphate (ATP) and glutathione remains high even in old age, and the cation pump K+ greater than Na+ is still intact. This fact is also true in deep supranuclear cataracts and primary nuclear cataracts. In subcapsular cataracts, however, the ATP and glutathione content decreases rapidly and the cation pump is defect.