I don't have anything to add on the anatomical side, but I can offer up a little math on the subject of telescopic vision. I can't point to any specific panels, but my gut tells me that Superman's demonstrated some pretty impressive distance-seeing in the past.
Since the Earth is curved, the surface of the planet can only be seen as far as the horizon. For an eye located six feet off the ground, the horizon (assuming level terrain) is located just 3.3 miles away. So when he's standing, he shouldn't be able to see anything further than that.
Of course, sometimes Superman is flying when he scopes out the terrain. At 100 feet, the horizon is 13.5 miles away. At a mile in the air, the horizon is nearly 98 miles away. At two miles, one can see 138 miles.
Now Superman has x-ray vision too, so I suppose it's possible he could use the two in conjuction and peer through the Earth at something impossibly far away. But this would mean that when he takes a glance at the next state over, he ought to be looking at the ground, and not straight at the horizon.
And speaking of super-vision, with the season premiere of Smallville coming up, I'd like a moment's gripe about the show's treatment of telescopic vision. A full episode was devoted to Clark discovering his X-Ray vision, and another full episode to his development of heat vision. Both were better than average episodes. But the show has also had him utilize telescopic vision on intermittent occasions, without ever commenting on it or mentioning it as a unique power. Sloppy writing.