Effect of heavy charged particles on the normal eye

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Objectives : Heavy charged carbon particles are one kind of radiation and have begun to be used as the treatment for certain kinds of malignant tumors. However, this treatment has never been applied on the eye. A trial study of its irradiation on the orbital malignant tumors has just started in Japan. Since few reports are available about its influence on the retina, we studied the influence of heavy charged particles irradiation on the retina and crystalline lens.Methods : Wister rats (8 week-old, weighting about 150g) were used in this study . Right eyes were exposed to heavy charged carbon (ィイD112ィエD1C) particles irradiation in 5 different single doses (1, 2, 4, 8 and 16Gy) under general anesthesia with ketamine, xylazine and urethane. Six animals without irradiation were used as controls. The opacity of crystalline lens were evaluated with a surgical microscope and flash ERGs were recorded to evaluate retinal function at 1, 3 and 6 months after the irradiation.Results : At 1 month … More after the irradiation rats irradiated 8 and 16Gy showed significantly high incidence of cataract, and at 3 months all mice irradiated 16 Gy showed mature cataract. At 1 and 3 months, there were no significant changes in the amplitude of the a-waves in ERGs in any dose, but the amplitude of b-wave decreased significantly in the rats irradiated 16 Gy. At 6 months after the irradiation, the rats irradiated 8 and 16 Gy showed statistically significant decrease of the amplitudes of b-waves, but the amplitude od a-wave remained normal. In the rats with lower doses, there were no significant changes.Conclusions : With single irradiation of 8 Gy and 16 Gy cause cataract shortly after the irradiation. The retinae were not damaged with low doses (1, 2, and 4Gy) of heavy charged particles. But high dose (8 and 16Gy) caused retinal functional damage in a long term, although it has no influence in a short term. Our results could provide important information to apply the ィイD112ィエD1C particles irradiation on the eye clinically. Less