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Bifocals: What Happened When Benjamin Franklin Got Old
If you have trouble with both near and distance vision, there’s a good chance you’ll need bifocals. Read on to trace bifocals’s path from invention to potential obsolescence.
After age 40, the world at hand becomes a little blurry for most people. They may find themselves leaning back from their laptop screens or holding the newspaper at arm’s length to focus on small type—an ability that’s been diminished by a natural stiffening of the eye’s lens, which reduces its focusing power. Unfair as it may seem, this does nothing to cancel out the effects of nearsightedness, so people who already wear glasses to correct myopia must pop bifocal lenses into their frames.
Benjamin Franklin was responsible for the first set of bifocals, which he assembled by simply sticking distance lenses into a frame above near lenses. Although the application was clumsy, the theory stuck around. Modern bifocals still have a lower region for looking at nearby objects such as a book or a hamster that you are making sure isn’t trying to talk to you. Versions with a near-vision panel embedded conveniently where your eyes will focus when reading are still in use, but they’ve been outstripped by no-line or progressive bifocals. In these, the prescription changes gradually across the middle, eliminating the sensation that images are jumping as your eyes cross a hard border. These, too, soon might become obsolete: there now exist lenses with a near-vision zone made of liquid crystal that’s activated by the tap of a finger or prehensile eyelash.