The gemara in עירובין יח has a very interesting discussion, it wants to know according to the מ"ד that אדם and חוה were created together back-to-back שני פרצופים, who walked first (i.e. which direction)?
And the gemara answers that
אמר רב נחמן בר יצחק מסתברא דזכר סגי ברישא דתניא לא יהלך אדם אחורי אשה בדרך ואפי' היא אשתו
Rav Nachman says it seems likely that Adam went first as we learnt that a man should not walk behind a woman even if she's his wife (loose translation).
Most מפרשים understand the reason being tznius (look here) as is the פשטות of the גמרא (look at the continuation), רש"י though gives a different reason (משום גנאי) regarding walking after ones own wife, (but look here (I don't see the main source on hebrew books, but this sefer quotes it) that even רש"י agrees that the main point is tznius (הרהור), but by ones wife were there is no real tznius issues it's just חשד since others might not know they're a couple).
So the question is since if חוה would be going first אדם would be walking backwards (and he can't see her) wouldn't that negate any problems? Do we see from here that it's אסור להלוך אחורי אשה ואפי' אשתו even if you can't see her???