Oh! You say there is no evidence for designer!
Ok you believe the good organ of body produced by natural selection and other maybe believe God create that good organ and that complex organ include eye, heart ,.... can't made by nature.
Ok but maybe you don't understand my question! I don't want you discuss on design and designer. I ask does the existing of blind spot and it's Innervation a necessary and good structure or not? (With out attention to evolution or God)
thank you.

http://www.askabiologist.org.uk/answers … p?id=14436

as I said in my original post the eye has evolved to exquisite complexity and the blind spot is more than compensated for by binocular vision and the ability of the brain to "fill in the gaps" by multiple images that are slightly different as we constantly move our heads. So... to specifically answer you question - the eye is amazingly evolved to an incredible degree of complexity and the blind spot in a necessary outcome of the exit of the optic nerve from the back of the retina. The positive advantages of the vision apparatus massively outweigh the minor disadvantage of the blind spot.