Yes, the ability to see very far away does imply in very large eyes if you define “see” by properly focusing on the objects. But not large pupils, what matters is the size of the eyes lenses, on the bare front of them.
But no, he could be able to perceive those stuff without the larger eyes if he had a good mental model of how the horsemen interfere with the background (what is probably easier than it seems, because would be moving), and how their hair would interfere with the previous outline.
Hope@lemmy.world 4 days ago
I don’t know enough about eyeballs to be able to answer, but 5 leagues is a bit more than 5x farther than eagles can see, and eagles already have larger pupils than humans do.