Glasses to protect your eyes!!!! Very few repairs are possible. I got new plastic lenses, but my retina and cornea and eyelid scars are forever.I have never needed glasses
And yes, glasses to focus. The so-called "normal" eye, relaxed, focuses at infinity (rounded to >20'). When young, it can tense-up to focus inside 1 foot. That's just close enough for 1960s electronics, and over time strains your eyes. A "+3.25" reading lens makes an infinity focus into a 1-foot focus, comfortable for hours. If you are under 40, you can strain-in more lens power and see well at a half-foot for short term.
I was near-sighted and always focused 13"-17". Reading bare-eye was comfortable, I could strain and see the tip of my nose or a phono needle, but driving required correction. Past 40 I also lost that near vision and collected near-lenses.
For simple "readers" magnification doesn't really happen, they allow you to bring the book/work closer so it looks bigger without going fuzzy.
Now that I am hard-corrected for infinity, I use +2 readers for a PC screen at arm's length, +3.25 or two +2 over each other (about +4) for small parts. Readers are rarely sold stronger than +3.25 or so. I buy basic readers for $1 at DollarTree. (But my all-day PC peepers are per my prescription, slight astigmatism, $8 at Zennis.) A friend just paid $20 for a pack of three +2.5 brand-name at the discount warehouse.