Eye Problems From Space Affect At Least 21 NASA Astronauts

A reader sends this report from Universe Today: How does microgravity affect your health? One of the chief concerns of NASA astronauts these days is changes to eyesight. Some people come back from long-duration stays in space with what appears to be permanent changes, such as requiring glasses when previously they did not. And the numbers are interesting. A few months after NASA [said] 20% of astronauts may face this problem, a new study points out that 21 U.S. astronauts that have flown on the International Space Station for long flights (which tend to be five to six months) face visual problems. These include "hyperopic shift, scotoma and choroidal folds to cotton wool spots, optic nerve sheath distension, globe flattening and edema of the optic nerve," states the University of Houston, which is collaborating with NASA on a long-term study of astronauts while they're in orbit.

Zero-G is bad long term, but what about 1/6-G?

[deathcloset]

This is an unintuitive wild speculation, but I wonder if these effects are a linear function of the gravity or if there is a more complex interaction.
In other words, if Alice spent 6 monts in zero-G and Bob spent 6 months in 0.166-G, and assuming equal eye health, would Bob have less damage than Alice or more?

Obviously the human body emerged out of a 1-G environment, so the eye has evolved with those pressures. But just because removing those pressures completely may result in harm, that is not to say that removing those pressures partially would be harmful.

The only non-zero-G astronauts I know of were the Apollo folks - but I can't find any information (or anectdotes from them) on the difference in physiological effects of zero-g versus 1/6th-G.

It seems like they would have experienced less intercranial pressure and would have had an actual reference for up and down.

Oh space be a harsh mistress.