Elves in LOTR have technically infinite vision because the world used to be flat and illuminated by two glowing trees that resided in Valinor. Because the world was flat, and Elves have essentially perfect vision at any distance, they could actually see things that were on the opposite side of the world.

After Morgoth (aka Melkor, aka the evil god that Sauron worships) and Ungoliant (the mother of Shelob, the spider that nearly kills Frodo) destroyed the trees then the world was made into a globe and Elves infinite vision ability, while still useful, wasn't quite as powerful as before.