To put it simply. How would the color an eye affect what one could see?

I ask this due to watching some of an anime called, "Somali and the Forest Spirit" If I remember correctly in episode 2 the main characters come across two members of an Oni clan. Now, these two Oni visually had eyes similar to humans, but their sclera was not black, but white.

That is when I began to wonder how would changing the colors of different parts of the eye affect what one sees, assuming this change isn't merely cosmetic, but in one's DNA, similar to how nocturnal animals' eyes reflect light at night.

Please let me know if you need further explanation by commenting. This is the first question that I have asked. Thank you! :)

  • $\begingroup$ uhh color certainly doesn't, shape does its called astigmatism and different size well that happens when your eyes dilate. $\endgroup$
    – Topcode
    Apr 19, 2020 at 2:11
  • $\begingroup$ So, having a solid black eye wouldn't have a visual difference from a white eye? $\endgroup$
    – Traveler
    Apr 19, 2020 at 2:16
  • $\begingroup$ Sure! I'll do what I can! $\endgroup$
    – Traveler
    Apr 19, 2020 at 2:25
  • $\begingroup$ @Traveler that depends on why it is that color, if your eye just has an extra pigment on the outside nothing should change but if its black because of a disease thats different. having a green vs blue eye does not effect vision to any noticeable degree $\endgroup$
    – Topcode
    Apr 19, 2020 at 2:30
  • $\begingroup$ The color of the eye affects eyesight in the same way that the color of the camera affects the photographs. (And the sclera of humans is white. At least on Earth.) $\endgroup$
    – AlexP
    Apr 19, 2020 at 3:24

2 Answers 2


Let's go by steps:

Size: bigger eyes mean more light can go in, which is why it's common for nocturnal animals to have larger eyes, along with other mechanisms to maximize the amount of light hitting the retina, like the tapetum lucidum, which gives the appearance that they're glowing when light is directed at them.

Shape: I assume you mean the pupils, unless you mean to talk about the owl's eye "tubes". Here's an image that sums up well: enter image description here

Color: the color of your iris doesn't really change how you see, but it might change how others see you. Colors tend to have psychological effects, so you could say red eyes have a chance of inspiring anger while baby blue might inspire calmness (which is one of the reasons why many monsters are drawn with red eyes). The presence of a large black iris can also be an advantage if you don't want others to know where exactly are you looking at, but can be detrimental in social species, in which the eyes orientation are important to signal certain messages.

Commenting on the black (?) sclera (ours is white so I assume you inverted by accident) , I have little to say. I've failed to find animals or humans with similar conditions, but the closest I found was a condition whee the pupil simply covers a large portion of the eye, making it look black. The black sclera might be so due to special pigmentation in this part of their eyes, and I doubt it'd actually change their vision, as the sclera's main purpose os keeping the shape of the eye.

  • $\begingroup$ Thank you @ProjectApex. Your answer is very helpful. $\endgroup$
    – Traveler
    Apr 19, 2020 at 2:45
  • 1
    $\begingroup$ All sclera in mammals are white. It happens that a great portion of it is visible in humans. The evolutionary reason for this is to allow stealthy visual communication, which is quite an advantage in a hunting party. The large contrasting white allows quick assessment of others' intentions without waving hands, making noises, shaking the head, etc. with are gestures more likely to alert prey. $\endgroup$ Apr 19, 2020 at 14:17

There is some evidence that brown eyes are better at tolerating bright sunlight and blue eyes give better night adaptation, but it's not on the level of superpowers.

The fact that nature hasn't evolved specific different colour schemas suggests there may not be much advantage compared to things like the camouflage effect of having eyes matching your fur colour.

  • $\begingroup$ Thank you, this is very helpful! $\endgroup$
    – Traveler
    Apr 19, 2020 at 22:38
  • $\begingroup$ It's known that owls eye color is a strong indicative of their preferred hunting time, so maybe there is an advantage beyond just camouflage $\endgroup$ May 31, 2020 at 14:26

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