[elric]

It's a bit of an oversimplification, but it's not too far off the mark. Human vision is pretty poor in terms of resolution and distance. But if you stop and think about it, it's incredible that we see as well as we do, or even at all! Proper vision requires a huge amount of brain real estate. The coordination of muscles involved in movements is incredibly complex. The eyeball is so special that it's got immune privileges no other body part has. The retina can detect a single photon hitting it.

[GeorgeTirebiter]

Yes, and... "However, the neural circuitry in your eye only passes a signal along to the brain if several photons are detected at about the same time in neighboring rod cells. Therefore, even though your eye is capable of detecting a single, isolated photon, your brain is not capable of perceiving it. "

Also, evolutionarily, it appears as if eyes were evolved 3 separate times. And: "Eyes and other sensory organs probably evolved before the brain" https://en.wikipedia.org/wiki/Evolution_of_the_eye (which is outstanding on this topic)

[meowface]

As the article states, certain parts of the eye like the retina are actually considered a part of the brain, too. They form from the same embryonic tissue that forms the brain.