Design flaw? If the eye came about by evolution, there is no design, if it was by design, shall we tell God about the flaw. You underestimate God.
The blind spot was put there on purpose, that is how God does things. Perhaps to illustrate that we need each other to see thing that we might miss. Sure, the brain fill in information, but it misses details and can be easily fooled. It is impossible to demonstrate the blind spot with both eyes opened. The testimony of two is true, thus two testaments.
I used "design flaw" in a neutral sense. Thank you for word-lawyering, though. It seems that is all creationists have going for them.