Clouding of the transparent protein in the lens of the eye. A certain amount of this clouding occurs naturally during life. The elderly do not, therefore see quite the same way as they used to since there is a slight yellowish cast in the clouded lens. Diabetics have an increased risk for cataract since high levels of glucose cause reactions with assorted proteins, including those in the lens; many of the reaction products are not optically clear, nor pack in the same way, thus altering the shape of the lens. There are both acute (changes more or less rapidly with changes in blood glucose), and chronic (longer term, slower changing) lens shape changes in diabetics, making eye examinations -- for vision correction, for instance -- somewhat tricky.