What Does It Mean to Have "Eagle Eyes"?

A person with eagle eyes notices everything and every detail, but having eagle eyes is as much about sight as it is insight. Like most idioms, the direct meaning of this saying is different from the implied meaning. Idioms use a comparison or metaphor for the sake of clarifying an idea. While they are usually clichés, idioms can still be used as effective forms of communication.

Idioms are sayings that mean something other than the literal meaning of the specific words they entail. They are frequently metaphors or similes, and due to their common use the meanings are implicitly understood by most people. The term "eagle eyes" is a metaphor for someone with acute powers of observation and insight. This person has a remarkably keen ability to direct his or her focus on an object. The idiom "eagle eyes" also suggests a predatory sense of perceptiveness due to the metaphorical allusion to a bird of prey.

The reference to an eagle is an apt one when describing someone with sharp powers of observation. Eagles are known for their remarkable vision. When hunting, these birds of prey frequently find the highest vantage point, like a tall leafless tree for instance, so that their vision is unhindered. Some eagles can spot a fish in water from several hundred feet in the air, even while flying. Since the color on the top of a fish usually blends with the color of the water this is no small accomplishment.

Idioms using animals are very common. Some examples are “bigger fish to fry,” which means that a person has more important matters to deal with than what is at hand. Another example is “beating a dead horse,” which means that trying to change something or someone’s opinion is to no avail, because it cannot be done. A person who is “all bark and no bite” does not back up their angry words with action.

Most idioms are timeworn sayings that people have heard over and over again. They do not necessarily make for great writing if someone is trying to impress other people with his or her powers of metaphorical creativity. Idioms can certainly get the point across though, and can provide an economical use of words. It is much more fun and colorful to say someone looks like “a deer caught in the headlights” than to tell someone that he or she appears to be caught off guard and cannot figure out how to react or what to say.

The term "eagle eye" has been in use since the Elizabethan age. It likely got its start as a comparison to the hunting birds that were widely used during that time. There are three common uses of this idiom in the English language.

A metaphor using eagle's eyes to indicate keen sight and perception is actually very apt. These birds of prey have eyesight that is exceptional by any standard.

Whereas 20/20 is considered the perfect vision for a human being, eagles can have 20/4 vision. This gives them an almost unbelievable ability to see small details from great distances. An eagle in flight is able to track the movement of a field mouse on the ground more than 600 feet below. This is one of the many features that make an eagle such a dangerous predator.

Without moving their heads, human beings can see what is directly in front of them and what is next to them. This leaves a massive 180-degree blind spot in human vision that can only be rectified by rotating the head and turning the body. In comparison, an eagle's vision takes in everything around them except for the 20 degrees of vision directly behind their head. Eagles also have the ability to use each eye independently of the other, allowing them to see in two opposite directions simultaneously.

In contrast to the small size of their head, eagles' eyes are nearly as large as a human's. Their eyes are protected by a series of three eyelids, the innermost being transluscent. As eagles blink, this thin membrane clears any debris from their eyes so that their vision remains sharp consistently.

Eagles have a skull structure that features a large brow bone that guards their eyes against damage. Additionally, their eyes are positioned so that they face forward, giving them both monocular and binocular vision. Although young eagles are prone to refractive problems, it is extremely rare for an adult eagle to have vision problems of any kind.

Due to cellular differences in eagles' eyes, they can see a much broader range of color than humans can. Whereas a human eye might only perceive the color blue, an eagle can see varying shades of blue. They are known to use color identification to choose which animals to hunt.

Eagles are also able to see ultraviolet light which is beyond the spectrum of human vision. This ability to see UV light means that eagles can see the urine trails that animals leave behind and track their prey by following these signs.

Saying that a person is eagle-eyed can be an indication of a variety of traits. It is a phrase that is used to describe both negative and positive intentions.

A person may be seen to be eagle-eyed if their intention is to protect. This can be true of childcare workers, law enforcement officers or bodyguards. Individuals in these fields remain vigilant to guard against any dangers to those under their care.

The phrase can also indicate that a person can be trusted to detect an error. It is an important quality for people with titles such as accountant, electrition or physician. The ability to discern even the smallest deviation from the norm is essential in these careers.

Watching someone with an eagle eye can carry the negative connotation of watching them with the intention of finding fault. Students may ascribe their teachers with this quality and working adults often feel this way about an unfair employer.

The phrase can also be used to describe a person who is keenly observing something or someone with nefarious or predatory intentions. For example, criminals might make an in-depth study of their target or victim in order to discover weaknesses they may be able to exploit.