Complex sentence: Ben Franklin had indeed invented bifocals, and perhaps 50 years earlier than had been originally thought.Benjamin Franklin was among the first to wear bifocal lenses, and Franklin's letters of correspondence suggest that he invented them independently, regardless that he was the first to invent them.
Split into simpler sentences: Ben Franklin had indeed invented bifocals, and perhaps 50 years earlier than had been originally thought. Nonetheless, Benjamin Franklin was among the first to wear bifocal lenses, and Franklin's letters of correspondence suggest that he invented them independently, regardless of whether he was the first to invent them.