That's fine for young people. But at age 65, my eyes do not have the ability yours may to focus at a variety of different distances. I use and recommend a pair

That's fine for young people. But at age 65, my eyes do not have the ability yours may to focus at a variety of different distances. I use and recommend a pair of single vision computer glasses. These are adjusted to let my eyes focus on a screen 20" away, which happens to be my viewing distance for a laptop in normal use. My eyes are completely relaxed when viewing a screen at that distance. I could have picked any other distance, like the farther distances discussed in the article, but then I would be stuck at that viewing distance. I wouldn't be able to use a laptop display at all but would have to always use an external display placed farther away. Since I do want to be able to use the laptop all by itself, e.g. when traveling, I had my glasses made for that 20" laptop viewing distance. So when I use a second monitor alongside my main laptop display (like the portrait mode 24" 4K monitor I use next to my high-DPI ThinkPad or MacBook at my home office), that monitor must be close to the same 20" distance, or it will be out of focus and I won't be able to use it comfortably.