Cats generally don’t use them unless their eyes are closed. It’s pretty vestigial for domestic cats, but my guy (pretty young less than six months old) sleeps with his eyes open, but the nictitating membranes shut. Makes him look kind of dead.
When we wake him up it takes him a few seconds to blink the membrane and his outer eyelids before he seems to gain focus.
He’s a weird cat. Likes belly scritches and never attacks when having his belly rubbed, I’ve trained him to fetch, and I’m pretty sure my brainwashing to make him act like a dog is working.