THE EFFECTS OF BETA RADIATION ON THE NORMAL CORNEAL ENDOTHELIUM OF THE RABBIT

No pathologic effects were noted in the eyes after local Sr/sup 90/ irradiation of the central areas of the right eye at doses of 6000 and 18,000 rep. Combined alizarin red and hematoxylin stains of the endothelium were used to study changes in the population of multinucleated giant cells, which were observed in the normal corneal endothelium of the control left eye. After doses of 6000 rep, the difference of multinucleated giant cell counts between the two eyes was within the normal limit for the first day, followed by a period of 3 to 7 days during which the formation of these cells in the irradiated eyes was temporarily inhibited. After this period of inhibition, an overcompensating increase of these cells was noted in the third postirradiation week, reaching its peak in the fourth week. By the end of the sixth week this effect had tapered off. After doses of 18,000 rep, the difference of the multinucleated giant cell counts between the two eyes was within the normal limit for the first day. A decrease in the number of these cells was noted in the irradiated eyes 3 days after irradiation. After this period of inhibition, an increase of thesemore » cells was noted in the first postirradiation week and the count rose consistently to the 6-week period when the experiments were terminated. Cytologic changes in the corneal endothelium were noted only in the doses of 18,000 rep in the 4- and 6- week period after irradiation but the extent of the cellular damage is not sufficient to cause biomicroscopically visible corneal lesions. No pathologic mitoses or nuclear fragmentation were observed with the doses and time intervals used. Perhaps insufficiently high doses of radiation were used to demonstrate these changes, especially in mitoses which almost always are limited to the peripheral endothelium. It is concluded that a BETA -ray dose of 18,000 rep is still not high enough to damage a large number of endothelial cells and, when only a few cells are damaged, these may eventually be replaced or, if the damage to a cell is not severe, recovery is possible. (BBB)« less