It's a very clever trick to take a quote out of context. Darwin answers this seeming problem he introduced when the paragraph continues:

"Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but I may remark that several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound".

Darwin continues with three more pages describing a sequence of plausible intermediate stages between eyelessness and human eyes, giving examples from existing organisms to show that the intermediates are viable.

Also, if the eye is the result of an "intelligent designer", then why is it so badly designed? Couldn't this "designer" (more commonly thought of as god) come up with an eyeball that doesn't have a blind spot? Even lowly old man designed both a film camera and a video camera, neither of which has a blind spot.

The alternative to Evolution is Ignorance!