Histologic Studies of Neutron- and X-Irradiated Mouse Lenses

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Abstract
Swiss mice were exposed to single or multiple doses of neutrons from a 37 inch cyclotron or to X-rays and the cataractous changes in the lens were studied. Radiation cataracts develop in 2 stages. The first stage resulted from damage to individual cells of the lens epithelium as indicated by derangement of the lens bow pattern, abnormal fiber elements in the cortex, undiifer-entiated cells migrating under the capsule from the equator toward the posterior pole, and accumulation of abnormal cells and debris at the lens poles. At low doses, the progression stopped at this stage. With higher doses, cataracts progressed to a second stage involving all the structures inside the capsule. At this stage, when the lens was completely opaque, degenerative processes involved lenticular fibers formed prior to irradiation and even the lens nucleus. Qualitatively, the effects produced by neutrons and X-rays appeared to be the same. The rate of change was also the same when cataractogenically equivalent doses were given. Quantitatively, however, 1 rad of neutron radiation produced as much histologic abnormality as did 4 to 6 rads of X-radiation. Furthermore, when doses that were cataractogenically equivalent as a single dose were given as fractionated exposures, the effectiveness of the X-radiation was very much reduced, whereas the effectiveness of the neutron radiation decreased very little, if any.