Effects of Ar-40 and Fe-56 ions on retinal photoreceptor cells of the rabbit: Implications for manned missions to Mars

Losses of photoreceptor cells (rods) from the retinas of New Zealand white (NZW) rabbits were detectable within 2 years after localized acute irradiation of optic and proximal tissues with greater than or equal to 7 Gy of 530 MeV u(exp -1) Ar-40 ions or greater than or equal to 2 Gy of 465 MeV u(exp -1) Fe-56 ions in the Bragg plateau region of energy deposition. Those limits were determined only from an analysis of variance of dose groups because the shapes of the dose response curves at early post-irradiation times are not known, a concern being addressed by experiments in progress. Losses of photoreceptor cells for the period 0.5-2.5 years post-irradiation, determined by provisional linear regression analysis, were approxiamtely 1.7% Gy(exp -1) and 2.5% Gy(exp.-1) for Ar-40 and Fe-56 ions, respectively.