It had to happen: Harry Potter has made wearing eyeglasses seem cool . . . so much so that opticians in the United Kingdom are claiming that sales of spectacles among children under the age of 16 have soared some 40% since July. It was then that J.K. Rowling’s fourth installment about the boy wizard, “Harry Potter and the Goblet of Fire,” was published. (Potter himself is bespectacled.) Eyeglasses as a hip accessory? That IS magic.