My horse gets this when he doesn’t have a fly mask on, the flies are bad and the wind picks up.
I’d put a mask on him, keep cleaning his eyes as needed. Sometimes a nice cool compress helps them if his eyes are puffy at all.
I have one horse who has to have a fly mask on 24/7 in the summer time because any type of wind that blows any dust in his face causes him to have icky eyes, and we have bugs all the time, no matter what time of day/night…And he can see just fine at night.
I’ve never heard of them not being able to see through a mask at night..
"Take the time it takes, so that it takes less time."
"Expect a lot, accept a little, reward often."