I Remember Art Linkletter and Darwin

Evolution does not have to produce an eye's structure, vision enzymes, an optic nerve, and an optic lobe simultaneously. Here's one possible scenario:

1. A nerve in a creature's head evolves for a purpose unrelated to vision.

2. A blob of vision enzymes evolves connected to the nerve, allowing vision. (The equivalent of an optic lobe is not necessary. Some jellyfish have eyes even though they have no brain at all.)

3. An optic lobe evolves, improving processing of visual data.

4. Complex eye structure evolves, improving vision.

These steps would all require numerous substeps, but this example demonstrates that it is possible for vision to evolve.