For Christians (or anyone else) who deny Darwinian evolution.

[Succubus]

There are several things wrong with that sentence, but let's stick to the one point. You would need a massive increase in complexity in the processing center to go from the binary light/no light to recognizing shapes and doing something about it that would be a survival benefit. What survival benefit preserved the increasingly complex (but useless) eye until the organism developed the vastly improved processing center?

You don't need a Cray computer to perform basic arithmetic functions, and you don't need a massively complex neural system to invoke a reflex action to a stimulus. No doubt you will now ask 'how could they evolve together'?
The answer is; they almost certainly didn't. It is highly likely the first hundred trillion of these creatures with their proto eyes and proto nervous systems did not have the two synchronized, not to the benefit of the creatures survival that is.

It's highly likely this primitive arrangement at first resulted in the creature freezing when light hit its proto eye and gained no evolutionary advantage. Now fast forward a ~million? years. A handful of UV photons hits the light sensitive patch and whatever passes for a muscular system goes 'kick' and the thing darts off to one side.
What happened to the recalcitrants, the first group? They were eaten!
Evolution in action.