Astronauts on the ISS experience vision changes — should Mars travelers be worried?

According to a new study, 70% of astronauts who have spent between six and 12 months aboard the International Space Station (ISS) experienced significant changes to their vision due to a condition called “spaceflight-associated neuroocular syndrome,” or SANS.

SANS involves symptoms like swelling of the optic nerve, flattening at the back of the eye and general changes in vision. It occurs when…