Steve Huffman, the thirty-three-year-old co-founder and C.E.O. of Reddit, which is valued at six hundred million dollars, was nearsighted until November, 2015, when he arranged to have laser eye surgery. He underwent the procedure not for the sake of convenience or appearance but, rather, for a reason he doesn’t usually talk much about: he hopes that it will improve his odds of surviving a disaster, whether natural or man-made.