What is the eye ?

On this page, let's learn about an eye.
How was the eye formed? Moreover, structure of an eye? What kind of thing is it that we can see normally? What is nearsightedness, and farsightedness ?
Let's look at anime and think about it.

ŸWhere is an eye (oculus) from?
ŸIn the case it looks normally
ŸWhat is nearsightedness?
ŸWhat are the eye glasses for the nearsightedness ?
ŸWhat is farsightedness?
ŸWhat are eye glasses for farsightedness ?