Description of bifocals by Benjamin Franklin
Growing up, I was the one member of my household that did not need glasses. I mocked the other members of my family as they stumbled around the house, bumping into walls (or perhaps I exaggerate). Eventually, of course, time caught up with me. Now, like many or most people my age, I have different vision issues at different distances.
At long distances I am mildly astigmatic. This means that at night the moon and stars appear as vertical smears. I have a prescription pair of glasses that corrects for this, but my astigmatism is mild enough that I generally get by without them ("generally" meaning I haven't put them on in years). They would come in handy if I wanted to do some serious stargazing, for example, so I'm glad to have them on hand.
I also have increasing difficulty focusing on close-up objects. This is due to the increasing stiffness of the lens of the eye with aging. I can still read a newspaper with some effort, but tiny print is essentially unreadable without help. Also reading menus in dimly-lit restaurants, etc. I therefore keep several pairs of cheap reading glasses around. I try not to wear them habitually. This is not an issue of vanity (I have no problem pulling my glasses out and putting them on in front of people) but rather because I find the focusing muscles of the eye weaken if not used (just like other muscles).
Benjamin Franklin of course addressed this issue of different visual problems at different distances by inventing bifocals. As one can see in the illustration above (also photos if you seek them out), the original bifocals had a two-part frame for each eye. This was replaced with a two-part lens and later with bifocals with no visible lines (because needing bifocals is apparently some mark of shame). Personally I find the original two-pane design much cooler:
However, with no aspersions to Benjamin Franklin, I have decided that bifocals are definitely not for me. Not because visually I couldn't use them but as an antidote to multitasking. TV commercials for bifocals always show people instantly shifting attention from the book they're reading to their angelic kids playing in the sprinkler, etc., but what if I don't want to instantly shift my attention?
I've found I rather enjoy putting my reading glasses on as a gesture of deliberate commitment to focus on what is directly in front of me. Or conversely, taking them off as in order to focus on what is happening at a distance. I pity the young punks who have no such physical mechanism for deliberately directing attention.