What would it be like to have three functional eyes?

Depends on where it is. example

@elbanditoroso yes on forehead for instance….

Just more 3D depth?

We would see quite a lot differently, but the type of difference depends on the positioning.
Centrally located on the forehead could help the centering of the other two eyes, increase distance judgement, and present a higher definition to the brain. Glasses and goggles would present a special problem, and bangs would be almost unheard of.
An off center location would not be terribly useful.
On the chin would be a disaster, especially when eating a hot pizza slice.

Also would depend on how your brain/nervous-system processed it.

Just one more eye I would have to make up.

Is this how the musical group Third Eye Blind got their name?

I submit, there would need to be supporting bone structure, and also a protective brow.

This would really throw off the look of the forehead. If you put the eye beneath a unified brow in-between the other two eyes, and lowered the nose, and sinuses, it would stretch the face downward.

The layout we have is nice, now that I really consider it that way.

We wouldn’t see any better than our standard stereo vision.

If it was on the back top of our head, that would be great for safety.

That depends on the location of the eye, and what part of the light spectrum the eye actually can see. Maybe it could also be a super zoom lens for extreme ranges.

These would finally have buyers.

Just below the naval would be an interesting spot.

@kritiper, so, a porthole in the pants?

@Ltryptophan I suppose one wouldn’t use it in the normal sense.

@kritiper wait how would you be thinking to use it?

Now what do you think?

No matter what you use a lap eye for, it would be weird to cover it up.

50% greater chance to poke your eye out. (With a third eye, no matter where it is.)