Do changes in the hydration of the diabetic human lens precede cataract formation?

Cataract formation in diabetic lenses has been attributed to polyol-osmotic pressure-generated influx of water. The ensuing swelling in the form of pocket and lake accumulations cause light scattering. The authors tested whether clear lenses of diabetic patients show different hydration properties than age matched normal lenses. Normal and diabetic human lenses were investigated for their nonfreezable water content by differential scanning calorimetry. The total water content of the lens sections were studied by thermogravimetric analysis. Non-cataractous diabetic lenses in all three regions showed a higher total water content than normal lenses. The nonfreezable water content, seems to increase with age in diabetic lenses and decrease with age in normal human lenses. Thus, hydration changes in human diabetic lenses precede cataract formation. While syneresis, the release of bound water into the bulk, is part of the normal aging process, it appears to occur in the younger diabetics only. In older diabetics syneresis is halted or even reversed. This may be due to the glycation of lens proteins in diabetic patients which tends to immobilize water and therefore, reverse the syneresis due to aging.