Numpty question - fly masks.

[Pixel]

This will probably seem obvious to most of you but do you leave fly masks on all night?
In my yoof we only had the browband with strings on type of fly protection which could stay on until all the strings fell off! Then when the masks started coming in I had my old pony who was partially sighted so of course I didn't want to leave it on in poor light in case he started bumping into things.
When I got dhorse I just carried on taking it off at night out of habit and tbh everyone else at our field does as well so I've never questioned it.
However!! Now at another yard, traipsed back up there this evening quite late to take his mask off and noticed a few horses still had theirs on. Do you think it would impair their eyesight at all in the dark, or can they see just fine? (NB steep field with uneven footing and bushes, not nice rolling parkland!).

I have no idea but I'd leave it on I had a friend who took her horses off in the rain as she thought it would be hard to see out of when wet. but that would be too many changes for me! my lot take theirs off for me so I gave up and they now do without unless they have an eye issue.

I leave ours on. One of our ponies has sweet-itch and rubs her face terribly if I don't. It is a little tricky to see through them in the rain, but the ponies seems to manage ok!

Ok thanks, I'd only thought about dark, not rain as well!