The effect of continuous low doses of X-ray irradiation on the rat lens.

PURPOSE To clarify the morphological changes in the rat lens after irradiation with continuous low doses of x-ray at different intervals. METHODS Male Wistar rats at the age of 8 weeks were irradiated with three doses of 2 Gy at intervals of either 1 week or 1 day. Over the period from the first week to the eighth week after irradiation, the eyeballs of the rats were enucleated progressively and changes in the lenses were examined morphologically. A comparison was made with specimens from control rats at each time of enucleation. RESULTS (1) Three doses of weekly irradiation: 1 week later, the lens epithelium and fibers at the equator showed mild swelling. Bow configuration was slightly disturbed. Eight weeks later, swelling and uneven height of epithelial cells in the equatorial area, irregular bow configuration, swelling of cortical fibers and epithelial loss and deformed nuclei at the central epithelium were observed. (2) Three doses of daily irradiation: 1 week later, mild changes in the lens such as uneven height of epithelial cells, irregular bow structures, and swelling of cortical fibers were observed. Eight weeks later, irregular bow configuration, posterior dislocation of nuclei, severe epithelial loss and marked swelling of cortical fibers were observed at the equatorial area. Epithelial loss and deformed nuclei of the epithelium were observed in the central area. CONCLUSION The lens was damaged by continuous irradiation even though the dose was low. The damage to the lens caused by daily irradiation was more severe than that by weekly irradiation. The main symptoms were degeneration and loss of epithelial cells and swelling of cortical fibers.