Structural damage to the rat eye following long-term simulated weightlessness.

To better perform space missions and develop human spaceflights, the eye health of astronauts is receiving increasing attention from researchers. In this study, we used prolonged tail suspension to simulate microgravity cephalad fluid shift in space to observe intraocular pressure (IOP) changes, retinal structure, and optic nerve damage in rats. We observed significant choroidal thickening and optic nerve demyelination lesions in the rats in each experimental group. At the cellular level, retinal ganglion cells (RGCs) survival was significantly reduced, optic nerve oligodendrocytes were reduced, and apoptotic factors and microglia-mediated inflammation-related factors were detected in both the retina and optic nerve. The severity of these changes increased with increasing tails suspension time. In conclusion, simulated long-term microgravity can lead to slight intraocular pressure fluctuations, choroidal thickening, reduced RGCs survival, and optic nerve demyelination in rats.