When humans go into space, especially for long durations such as staying on the International Space Station, they experience significant changes in their vision. In some cases, these changes can lead to permanent vision loss or impairment.

What happens to the human eye in space? 
1.  Fluid shifts in microgravity. On Earth, gravity pulls fluids like blood and lymph down toward our zenith, or feet. In microgravity, that fluid redistributes toward the head, including the brain and eyes. This increases…