DISTRIBUTION AND TYPE OF MORPHOLOGICAL DAMAGE IN HUMAN NUCLEAR AGE-RELATED CATARACTS

The distribution and type of fiber cell damage was evaluated in human age-related nuclear cataracts and in aged normal (non-cataractous) len ses. Ten age-related nuclear cataracts (53 to 89 years old) and four n ormal lenses (59 to 67 years old) were examined by electron microscopy of fixed Vibratome sections. Images from the adult, juvenile, fetal a nd embryonic nuclear regions were compared. Each cataractous lens cont ained a central region of increased Light scattering which involved th e embryonic and fetal regions with progressively less involvement in t he juvenile and adult nuclear regions. Some damaged fiber cells were o bserved in all specimens, although damage was minor and infrequent in the normal Lenses. Degeneration of single or groups of fiber cells was noted in all the adult nuclei of the cataractous lenses, becoming les s frequent in the juvenile nuclei. The types of damage included locali zed voids, multilamellar membrane aggregates, globular bodies, enlarge d cells and regions of highly convoluted membranes. The fetal and embr yonic nuclei of the cataractous lenses exhibited rare and minor morpho logical defects, and were virtually identical to the equivalent region s of the normal aged lenses. Examination of cell interfaces in opaque regions of cataractous lenses revealed that the oldest fiber cells sus tained apparent membrane loss. Extracellular spaces in the embryonic, fetal and juvenile regions of the cataractous lenses often contained d ense. deposits, presumably cytoplasmic material lost from adjacent fib ers. The results indicate that the region of greatest nuclear opacity, located in the lens center, does not contain any significant cellular damage. This suggests that older fiber cells respond differently to p athological and senescent changes than younger cells made after fetal development. The observed loss of membranes and cytoplasmic material f rom the oldest fiber cells may be a contributory mechanism in the form ation of age-related human nuclear cataracts. (C) 1996 Academic Press Limited