behind the lens there are tiny little pixels, each pixel corresponds to another "flat" side of the lens, if your lens is not spherical, then your vision will be blurry, because the wrong rays are hitting the pixels. double slit experiments are humbug. its why i put "rays" into quotes. rays also from latin Radius- "rays/spokes that emanate from a common center, developing uniformly on all sides". rays arent realy real but important mathematically and geometrically.