The ID argument that the eye is irreducibly complex has been kicking around since Darwin's time (it was Darwin who acknowledged it.) However, recent research, particularly surrounding a conserved transcription factor called Pax6, have seriously undermined this common ID argument.
Go here and type 'eye, evolution, review' for the latest reviews on the literature.
Couple of recent articles:-
Arendt D (2003). Evolution of eyes and photoreceptor cell types. Int J Dev Biol. 47, 563
Treisman JE (2004). How to make an eye. Development. 131, 3823
Nilsson DE (2004). Eye evolution: a question of genetic promiscuity.
Of course, none of this precludes the existence of God. It simply supports the notion that eyes, like all other structures, appear to evolve from a common ancestral origin. It makes absolute sense really; even an incredibly crude collection of photosensitive cells can give an organism a significant advantage over its competitors, and thus send that photoreceptive organ down the path of natural selection and evolution.
Of course, the most important thing is not to subscribe to the 'well, science hasn't come up with the answer so it must be God' argument. As has been shown with the eye, you have to give science a chance to tackle the problem before you dismiss it out of hand.
Beg your pardon.
Go here and type 'eye, evolution, review'.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&itool=toolbar