That sounds a lot like what I used to to when I was a kid before I realized I needed glasses…
You might ask him if he has a hard time seeing what’s on the TV or if he can distinguish each individual leaf in a tree that’s 15 or 20 feet away (I’m suggesting you point at a tree and ask, not say “15 feet” to a 2 year old, just to clarify), or when someone he knows is a little distance away, say, “Can you tell who that is?”