An eagle eye just makes the target appear larger. This canmake it easier to see, and therefore easier to hit. However eagle eyes are not a cure-all, and AFAIK cannot be used in 10m air competition.

Personally I believe a lens prescribed specificaloy for shooting, by an optician who understands the game, and worn in glasses or attached to the rearsight (rules allowing) is better. A prescription lens will focus the eye at the correct spot (ahead of the foresight) for a sharp foresight and a not-too-blurry target, with no strain on the eye muscles. An adjustable rearsight dioptre, as made by Gehmann and Centra, can give the focus, and does enlarge the target, but isn't ideal.