Also, vertebrate eyes (left below) have a blind spot because the nerve wiring is routed in front of the retina and needs a path to get out of the eyeball, so there's a spot with no photoreceptor cells where all the fibers run out.
It doesn't have to be this way - cephalopod eyes (right) have the nerves running out the back of the retina so they don't need a pass-through hole.
"In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move."