Differential scanning calorimetric measurements on human lenses.

Differential scanning calorimetric measurements were performed between - 30 degrees C and 15 degrees C. The cortical sections of normal human lenses usually show one endotherm at the melting point, while the nucleus indicates a composite endotherm that can be separated into two endotherms with two melting points. Cataractous human lenses usually have composite endotherms from the cortical, intermediate as well as nuclear regions. We interpret the different endotherms as representing different kinds of freezable water contents: free water and partially bound water. Both in normal and cataractous human lenses, there is an appreciable amount of non-freezable water. The amount of non-freezable water is less in cataractous lenses than in normal lenses, indicating a syneretic process as a cause of cataract formation.