Biologist have long noted the similarities between the eyes of an octopus and the eyes of a human.

Scientists are currently debating whether we and octopuses evolved eyes separately, or whether a common ancestor had the makings of the eye.

This is not under debate. This is one of the classical examples of convergent evolution. From: http://en.wikipedia.org/wiki/Convergent_evolution#Eyes

One of the most well-known examples of convergent evolution is the camera eye of cephalopods (e.g., squid), vertebrates (e.g., mammals) and cnidaria (e.g., box jellies).[22] Their last common ancestor had at most a very simple photoreceptive spot, but a range of processes led to the progressive refinement of this structure to the advanced camera eye — with one subtle difference: The cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from the back of the retina, rather than the front as in vertebrates.[8] The similarity of the structures in other respects, despite the complex nature of the organ, illustrates how there are some biological challenges (e.g. vision) that have an optimal solution.

More info: http://en.wikipedia.org/wiki/Cephalopod_eye