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 they would be moving), and how their hair would interfere with the previous outline.