Eagle eyes are designed for clear vision in daylight, from early morning light to high noon and then on into the evening, but the pupil isn't big enough for night vision.
An eagle's skull is designed to shade the eyes from overhead sun, and to allow the eagle to see in front and below, with less visibility above and behind. This is because eagles are the hunters far more than they are the hunted!

Bristles at the base of the beak protect the eyes from dust and other particles while the eagle is flying. The nictitating membrane (inner or third eyelid) blinks much more often than the other eyelids, protecting and keeping the eyes moist while allowing clear and steady vision. The eagle's brain figures out where the fish is even though refraction of light at the water's surface makes the fish appear to be in a slightly different place.

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