I want to kick a dead horse here. I'm aware none of you have answers, and get upset about it. But for those of you who enjoy problems and thinking of solutions instead of regurgitating Dawkins, here are two more issues the eye needs to solve during its evolution:

1. Size Constancy: When you study the eye you come to realize that photoreceptors are the least interesting part of the visual system, and the real work goes on behind the scenes. You can begin to understand why with problem. A certain ball at a specific distance produces an image on the retina. If the ball becomes larger, the image on the retina also becomes larger. However, if the size doesn't change but the ball gets closer, the image becomes larger as well. The brain keeps the image constant despite its changing retinal size.

2. Shape Constancy: Same concept as above, except we focus on shape. Two things need to be correlated: the objects actual shape, and the shape of the object on the retina as it slants and changes direction. You still perceive a book as a rectangle, even if the image on the retina is a square or a trapezoid.

Without size constancy, an animal would run away at the sight of a nearby mosquito, because it looks giant on the retinal image; but it might not run away at the sight of a predator in the distance because it appears small. Likewise without shape constancy, you wouldn't be able to recognize a predator at all, since the shape would shift and morph aimlessly without reason.