Three eyes and vision

I was looking at buddhist paintings, and saw all these deities with three eyes. It got me wondering, how would having three eyes affect vision? I know that two eyes (when positioned right) gives binocular vision, but what would a third eye give?

Probably not much, except to give you a wider field of view depending on where the third eye is placed. You shouldn’t get any additional powers of perception. If you could move them independently like a chamelion, that would be a different story.


With ONE eye, I am able to perceive TWO dimensions…

With TWO eyes, I am able to perceive THREE dimensions…



Watch out, girls: I’ll be able to anticipate your objections to dating me and overcome them with my incredible powers of logic and picking lottery numbers.

Third eye, eh? Might want to check out the pineal gland.

Well, i’m talking of an actual third eyeball, not some theory regarding the pineal gland and new age stuff ;).

I think depth perception will improve slightly. With two eyes, there are certain scenes that confuse depth perception, like repeating patterns. A third eye can remove the ambiguity in such a case. But most of the time it doesn’t add much benefit.

One disadvantage is that it will be very difficult to design 3-D displays and stereograms. Such simulated 3-D displays work by providing an appropriate image for each eye. There are simple methods of providing two images to two eyes, but three will be more difficult.

Also, since the third eye is largely redundant, there is the possibility of giving it special capabilities. If I could get a third eye, I’d want it to have extra low-light sensitivity - i.e. larger size, more rods than cones, and an inverted retina like squids and octopi have. (Blood vessels behind the retina instead of in front.) Some snakes (cobras?) have an extra organ sensitive to infrared, but that would be difficult on a warm-blooded animal. (The eye itself, if warm, emits infrared.)

an extra eye to wink? *wink wink *

Your average insect has compound eyes. What looks like two eyes is actually hundreds of tiny eyes grouped in two clusters. Spiders have eight eyes. Sadly, a direct comparison to human vision is not possible. The eyes of arthropods, taken individually, offer a much poorer image than our own.

Of course the third eye seen on Hindu deities gives them spiritual vision, rather than looking out onto the material world.

Well, the operation of the pineal gland isn’t really the biggest mystery, and in many lizards it actually appears just below the surface as a light receptor; ie-a third eye. Only in mammals has it retreated, but it still has ties with the eye signals to perceive light.

Not sure why ancient-ish peoples had such an obsession with such a small part of the brain, though.

I suppose the big question is, where is this third eye going to be located? Three in a row, equilateral triangle, isosceles? Independent vision? It will, if in triangular form, definitely increase peripheral vision range. I don’t think it will allow for any higher resolution of anything, or better direct vision.

The biggest problem, of course, is how you’re gonna block Moe’s eye-poke. There’s an evolutionary theory there, somewhere…

I would imagine that (assuming the three eyes are in triangular arrangement) perception of depth would be heightened*, if the eyes were arranged merely in a horizontal straight line, there probably wouldn’t be much difference against the way we see with two eyes.

*I’m basing this assumption on the fact that many birds of prey will cock their heads to one side and back, so that they are getting binocular vision in both horizontal and vertical axes.