i know its hard to believe that something as complex as an eyeball can have simply evolved.  but actually, it has.
we had a discussion in my evolutionary theory class, where my professor explained that scientists have traced simple sequences of the mutations where the eye has formed by looking at the eyes of fishes, where they are believed to have evolved in less than 400,000 years ( i think?, you'll have to confirm that, i'm too lazy to Google it.)  also, darwin argued that by inheritance of eye mutations that have adapted to environments over thousands of years, it's not too difficult to think that an eyeball evolved.
besides, wouldn't you agree it's alot more believable than some fairy tale god in the sky just creating an eyball and sticking it in your socket?