The low levels of gravity (microgravity) in space cause significant changes in astronauts' eyes and vision after six to 12 months aboard the International Space Station (ISS), according to a study published in the IEEE Open Journal of Engineering in Medicine and Biology.
I don’t think a lunar free return trajectory would be long enough to measure this. Because the moon is so close.
Correct. But a lunar free return trajectory is about the limit of what I’d sent unsupervised monkeys on. ;)