Our minds take the images from each eye and combine them to make a complete picture. I can only imagine your mind does something similar, though the picture it creates much be so much more complete.

[Sharper, cleaner. Ignis can think of so many ways the image would be better than the one created by someone with just two eyes, but that is assuming her eyes work anything like a human's do. For all he knows, they may not.]

Damage to even one eye can be devastating. I've heard soldiers who have lost some of their sight in battle mention they would prefer to be completely blind as opposed to having to deal with the confused signals their brains create with only partial vision.