eagle eye

The eagle eye is among the sharpest in the animal kingdom, with an eyesight estimated at 4 to 8 times stronger than that of the average human. Although an eagle may only weigh , its eyes are roughly the same size as those of a human. Eagle weight varies: a small eagle could weigh , while a larger one could weigh ; an eagle of about weight could have eyes as big as that of a human who weighs . Although the size of the eagle eye is about the same as that of a human being, the back side shape of the eagle eye is flatter. Their eyes are stated to be larger in size than their brain, by weight. Color vision with resolution and clarity are the most prominent features of eagles' eyes, hence sharp-sighted people are sometimes referred to as "eagle-eyed". Eagles can identify five distinctly colored squirrels and locate their prey even if hidden. In addition to eagles, birds such as hawks, falcons, and owls also known as raptors have extraordinary vision which enable them to hunt for their prey more easily. Raptors are also known as "birds of prey" and are categorized by their predator hunting style. This means that they use their sharp senses to locate and capture prey. An eagle is said to be able to spot a rabbit 3.2 km (~2 miles) away. As the eagle descends from the sky to attack its prey, the muscles in the eyes continuously adjust the curvature of the eyeballs to maintain sharp focus and accurate perception throughout the approach and attack. Eye anatomy and physiology The outer most region of the eye is the cornea; light passes through the cornea first. Light is then refracted when passed through the cornea given its curved convex shape. "The image formed by the cornea is upside down and reversed from right to left."(Journey N, 1997-2019) The layers of the cornea in raptors include: the Anterior corneal epithelium, Anterior limiting lamina (Bowman's layer), Substantia propria (stroma comprising the majority of corneal thickness),Posterior limiting lamina (Descemet's membrane) Posterior epithelium (endothelium). The iris in eagles appears yellow and functions similarly to the iris in humans. The iris contracts and dilates to control the amount of light received by the retina. The muscles of the iris "striated muscle, smooth muscle, and a myopepithelial dilator muscle" Tucker, V. A. (2000–12) when contracted change the appearance of the pupil size. Eagles have large transparent lenses that have the ability to change shape.