Why Do We Have Two Eyes?

Human Eye- Why do Humans have 2 Eyes?

Close your right eye and mentally note your field of vision with only the left one. Now try the same by closing your left eye. Okay now stop closing your eyes and appreciate the full field of vision available to you on account of your TWO EYES!

Human Eye

This is one of the main advantages of us having two eyes. We have twice as much vision, so to speak. For an average well functioning pair of eyes, this binocular vision has a field of around 170o.

Try another experiment. Now that both your eyes are open, notice the brightness level of your current surroundings. Now alternate between keeping either eye open. Does the brightness level change (field of vision doesn’t very much either does it)? If your eyes are functioning properly, it probably isn’t. So what’s happening? Your eyes are actually seeing only from one eye at a time but alternating very rapidly. So fast in fact that you aren’t able to notice this. This process is also optimized for double eye vision.

The problem of parallax error in vision is reduced a lot because of this double eye vision. It also enhances our depth perception giving us a very good evolutionary advantage. Also, our ability to detect faint objects is more distinct. Thanks to our ‘two’ eyes, humans are able to enjoy stereoscopic vision. 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.

Human Eye 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!

The following question may have popped into your head. If we have two eyes, why do we still see a single image? Why not two different images? Why do you think?

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Practise This Question

Label the eye parts correctly.