Eagle vision would mean 20/4 resolution, built-in magnifying glasses, and the ability to perceive an inconceivable array of colors.
Eagles fly at an altitude of thousands of meters, in a manner similar to modern war planes, yet are able to comb the landscape below in staggering detail. The eagle can detect even the slightest of movements or color changes while in flight. It owes this ability to a very special eye structure. However, eagle's eyes cannot zoom. It can see sharp images from a distance.
In humans, the portion of the retina with the most acute vision is the fovea centralis, which has the highest concentration of cone cells. Eagles have two foveae, giving them an incredibly sharp sense of sight. Humans have only one fovea in each eye-for binocular, or forward vision. When we look at an object, both our eyes are directed toward the object. This allows our brain to merge both the images to create a sense of depth. The eagle contains a binocular fovea like ours, but also has a fovea for monocular vision that allows each eye to look sideways and see a separate image. So eagles can see both forward and to the side at the same time.
The eagle has a visual perspective of some 300 degrees, as well as an extra focusing power. Humans change the shape of their lenses to focus. But an eagle can change the shape of both lens and cornea. This gives it extra focusing power. It can also scan a 30,000-hectare (116-square mile) field from an altitude of 4,500 meters (14,700 feet), or spot a camouflaged rabbit from 90 meters (300 feet) with ease.
To attain this super-sharp vision, an eagle's retinal cells are tinted with special colored oil droplets, increasing the contrast for objects seen against the blue sky or green forest. Thanks to this, the eagle can spot minute changes in contrast from thousands of meters above and swoop down to hunt.
Coming to lenses, they are made glasses and can be focussed and/or zoomed according to our wish. There can be a variety of different lenses, from wide-angle to telephoto lengths. A camera lens can create a brighter picture with less light than an eye can, simply because it can collect light over a period of time. The eye can only use the light visible at one instant.
If you swapped your eyes for an eagle's, you could see an ant crawling on the ground from the roof of a 10-story building. You could make out the expressions on basketball players' faces from the worst seats in the arena. Objects directly in your line of sight would appear magnified, and everything would be brilliantly colored, rendered in an inconceivable array of shades.