Abstract
Examination of normal human lenses varying in age from 3 months to 89 years indicates that there is a gradual increase in the per cent high molecular weight protein (HMWP) in the soluble fraction commencing in the second decade of life, which reaches approximately 12 to 15 per cent in old lenses. Studies on isolated cortical and nuclear regions of the lens have shown that this process occurs almost entirely in the nuclear region. Little nuclear HMWP is detected before the age of 25, after which it increases rapidly to reach levels of approximately 30 per cent of the total solubleprotein in very old lens. Little HMWP can be detected in the cortex before the age of 40 and maximum levels of from 4 to 7 per cent are found in lenses of approximately 80 to 90 years. Quantitative analyses of lens light back-scatter indicates that in the nuclear region the increase in backscatter parallels the increase in HMWP while in the cortex, back-scatter appears to be independent of HMWP. It is proposed that cortical back-scatter is due to intrinsic morphologic characteristics while nuclear back-scatter is dependent upon the concentration of HMWP.