Ditto don't trim the eye whiskers.
Now that I've said that, I will trim the whiskers on the top
of the eyelid during fly mask season IF they get so long that the fly mask bends them down into the eye.
My horses live in fly masks as soon as the flies come out in the spring until they stop flying around in October or November.
I use those little two inch children's scissors with the fairly round ends on them because it's natural for the horse to jerk when something gets near its eye.
It isn't something I make a habit of but, again, if the eye whisker is so long that the fly mask makes go into the eye, then I trim it