This work aims at investigating the interactions between the flow of fluids in the brain and eyes, and their potential implications in the development of visual impairment and intracranial pressure (VIIP) syndrome in astronauts. We propose a reduced (0-D) mathematical model of fluid circulation in the eyes and brain, which is embedded into a simplified whole-body circulation model. This model allows us to predict fluid redistribution in the upper body vasculature as well as variation of the intracranial (ICP) and intraocular (IOP) pressures. The model results suggest that, by taking into account some eff ects of microgravity, it is possible to observe, on one hand, an increase in IOP, and on the other, a decrease in blood flow circulation in the choroid and ciliary body. These findings provide clues for the role that vascular components may play in VIIP pathogenesis, for which astronauts could be screened on Earth and in-flight.