What Is the Use of Having Two Eyes?
The fact that we have binocular vision – that is, vision through two eyes – helps us to perceive depth. Our eyes measure about two and a half inches from pupil to pupil.
Therefore, the right eye sees more of the right side of an object, and the left eye sees more of the left side. This gives us stereoscopic vision, or the ability to judge depth.
Stereoscopic vision enables us to see that an object is solid or deep, or in front of or behind something else. Try looking at an object with only one eye. You will find that it looks much flatter than it does with two eyes.
The two eyes provide vision which is additive by enabling a wider field of vision when using two eyes compared to one. The two eyes also cooperate in the overlapping visual fields enabling stereoscopic vision by blending slightly dissimilar views of an object which is then seen singly and with depth.
Some animals with two eyes like rabbits and buffaloes have 360o degree field of vision but they do not have stereoscopic vision. This is an advantage only available to animals with two eyes in the front of their head like us humans.
Two eyes also present an aesthetic advantage. Symmetry is always considered to be more appealing than asymmetry. Two eyes satisfy this condition. Apart from the significant advantages mentioned above, there is another extremely important advantage of having two eyes. If one dies, there’s always a spare!
With normal vision, both eyes aim at the same spot. The brain then combines the two pictures into a single three-dimensional image. This three-dimensional image gives us depth perception.
When one eye is out of alignment, two different pictures are sent to the brain. In a young child, the brain learns to ignore the image of the misaligned eye and sees only the image from the straight or better seeing eye. The child then loses depth perception.
Adults who develop strabismus often have double vision because their brains have already learned to receive images from both eyes and cannot ignore the image from the turned eye. A child generally does not see double.
Is it possible to have two colored eyes? Heterochromia iridium (two different-colored eyes within a single individual) and heterochromia iridis (a variety of color within a single iris) are relatively rare in humans and result from increased or decreased pigmentation of the iris.