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.