Meanwhile I am trying to think of the shape that gives a further focal point

3.5 cm pupils? I've heard of "wide-eyed" but this is ridiculous!

But I never knew a "league" was 3 miles. That's like, a lotta football fields!

I remember somebody making the argument that due to the diffusion of light he would not be able to discern their features at all.

I feel it is very important to post this here:

Some rough calculations:

5 leagues ≈ 15 mi ≈ 24.1 km. An average human has hair that's maybe 20 cm wide. Using the small angle approximation we get an angular size of 0.2/24100 ≈ 8.3x10^-6 radians.

At 400 nm wavelength, resolving details of that angular size requires an aperture of 1.22(400 nm / 8.3x10^-6) ≈ 5.88 cm.

So either Legolas has some absolutely massive eyes, has the ability to use both his eyes for optical interferometry (I'm voting for this since it's the coolest), or is just plain magic.

With coherent detection I think the separation between eyes would allow for this.