Histologic Studies of Neutron- and X-Irradiated Mouse Lenses

Radiation cataracts seemsd to develop in two stages. The first stage appeared to be the consequence of damage of individual cells of the lens epithelium. The resultant histological ahmormalities were: (1) derangement of the lens bow pattern, (2) abnormal fiber elements in the cortex, (3) undifferentiated cells migrating under the capsule from the equator toward the posterior pole, and (4) an accumulation of abnormal cells and debris at the lens poles. At low doses, the progression stopoed at this stage. With higher doses, cataracts progressed through this first stage to a second stage which involved all the structures inside the capsule. At this stage, when the lens was completely opaque, degenerative processes involved those fibers formed prior to irradiation and sometimes even the lens nucleus. Quarlitatively, the types of damage produced by neutrons and by x rays were apparently no different. The rats of changes was also the same when cataractogerically equdvalent doses of neutron and x radiation were employed. Quantitatively, however, 1 rad of neutron radation produced as much histolquic abaormality as 4 to 6 rads of x radiation. Futhermore, when doses that were cataractogenically equivalent as a single dose were given as fractionated exposures, the effectivensss of themore » x raniation was very much reduced, whereas the effectiveness of the neutron radiation decreased very littls, if any. (auth)« less