Eagle Sight & Human Sight

Eagles are beautiful birds known for their majestic frame and incredible hunting abilities. They have the reputation of having one of the best visions on the planet. What makes ‘eagle eyes’ a thing of envy? Let’s find out.

VISUAL ACUITY

Visual acuity is the eye’s ability to separate details of an object without any blur. The normal or a ‘good’ vision for a human is 20/20. Eagles, however, have retinas with cones and have a much deeper fovea—a cone-rich structure in the back of the eye. These give them a visual acuity of an impressive 20/5, or 20/4 which allows them to hunt even the tiny prey from hundreds of feet up in the air.

HOW IS THE EAGLE’S VISION MEASURED

There is a scientific set-up to determine the strength of eagle’s vision. The birds are trained to fly down a long tunnel where two TV screens are kept at the end. One screen has a display of striped pattern to attract the eagle towards it and when they land on that screen, they are given a treat. The birds’ acuity is tested by changing the width of the stripes and determining from what distance the eagles begin to turn in the correct direction.

THE RANGE AND VIVIDNESS OF COLORS

Eagles have the ability to see colors more vividly than humans can. They can even see ultraviolet light and pick out more shades of one color. Their ability to even see the UV light allows them to see the bodily traces left by their prey. Mice’s and other small prey’s urine is visible to the eagles in the ultraviolent range, making them easy targets even a few hundred feet above the ground.

POSITIONING OF THE EYES

Human eyes are positioned at the front of the heads, giving us a binocular vision and a peripheral vision of just 180 degrees. We can only see complete images when we use both eyes, as closing one will block a portion of vision that was visible with that eye. The use of both eyes gives us that ability to determine the depth of field and help us realize the speed of any moving object. Unfortunately, our peripheral vision is quite poor.

On the other hand, an eagle’s eyes are rotated towards the front of the head and are angled 30 degrees from the midline of the face. This allows them to have a 340 degree field of vision. Their peripheral vision is quite impressive, which greatly assists these predatory birds.

ABILITY TO FOCUS CLEARLY

The ability to switch between seeing things that are near and far clearly require quick changes in the lens of the eyes, which is known as accommodation. As humans age, the muscles required to change the shape of the lens get stiff and become less effective, requiring us to wear glasses to see distant and nearby things equally clear. However, the eagles not only have a lens that changes the shape to accommodate the changing distance but even their cornea has the ability to change shape to better focus on near and far objects.