VIsual System Activation by Ionizing Radiation: Modelling the irradiation setup for whole rabbit eye exposures

The earliest evidence of space radiation effects on brain functions has been the perception of phosphenes (flashes of light), reported by astronauts since the Apollo missions. The recently reported effects of radiation on sensory channels other than visual suggest, besides the largely investigated activation of retinal processes, a direct action of radiation on neurons or neural networks. In particular, ionizing radiation may influence the biological signaling mainly due to calcium ion homeostasis. In this context, within the VISAIR project we are conducting an experimental study with ex vivo whole rabbit eyes, maintained bio-active in a suitable medium, to investigate the activation of the visual system and analyze possible modulation of the effects with different LET/Z. Modelling is needed to interpret the results and extrapolate findings to radiation rates relevant for space exploration. We here present representative results obtained with the code PHITS, after implementation of a software replica of the experimental setup, to verify dosimetric quantities and characterize the radiation field in the target eye.