How could evolution make the shark's eye a perfect sphere? How can this be determined

Shouldn't this involve deep knowledge of light physics to begin with? Please provide a reason better that just "time" in millions of years.

Liquid in a flexible container naturally takes the form of a sphere.

Does a rock need "deep knowledge" of gravity in order to fall down? No, it just does. Does the shark need to know why its eye works well? No. If the eye works well, the shark survives and reproduces. If it doesn't, it doesn't.

This follows directly from the most basic evolutionary principles.