Slit pupils are a trait exclusively seen on ambush predators who stay low on the ground like cats, crocodiles, snakes, etc, its use is that it provides an ample vertical field of view that massively increases depth perception at the cost of a smaller field of view.
You can actually see the opposite case on goats, horses, sheep, etc, who have a horizontal pupil that maximizes field of view at the cost of depth perception, but it ain't an issue to them since all they need to know is if there's a predators trying to jump them while they're grazing.
That brings us to circular "lens-style" pupils, they're a mix of both, pretty much. Good field of view and depth perception, which is the go-to for basically most animals on earth, including some unexpected predators! For instance: Tigers, jaguars, lions and every other large cat has round pupils, since they're not low to the ground like small cats and some lizards. Same goes for every bird, especially birds of prey like owls and hawks, since they'll always be watching their prey from above and slit pupils are completely useless for that end.
All that is to say: Pretty much every dragon and mythical lizard: flying western ones, eastern ones, drakes, wyverns, sea serpents, leviathans, wyrms, lizard people, hell, even most dinosaurs... all would have round pupils. The only exception possibly being particularly small flightless dragons, and maybe kobolds. Slit pupils have a powerful association with lizards, I know, prolly why I see it so often in art, but slit pupils are a niche exception, not the rule!
Ultimately, draw however you want, I just wanted to give my two cents for folks that might care about that sort of thing :D
This post covers what I was saying about dragon eyes yesterday, while quoting the same person no less. π₯΄ But yeah, absolutely this. Glad to see others care about such things. β€οΈ
