I think its a bit of both.

Personally, I apparently focus (that's what it's called, right? Non native speaker here) slightly behind infinity, so I'll have to put a slight amount of effort into seeing clouds clearly. I can also focus on close objects, but if I read a book for about 5-60 minutes without my glasses I'll suffer a splitting headache, depending on how much time I've used inside recently.

I've found that I can do office work just fine using glasses, but after a few months I'll need to get stronger glasses as my eyes become worse. This resets if I spend a few days outside avoiding computers, books, and my glasses entirely.

I can usually watch TV just fine without glasses, but if I've been doing office work or just been mostly inside for about 2-3 months I'll need my computer glasses (tuned to focus at around 50-100cm) to watch the TV (located about 3 meters away). At this point, I usually also have to use my reading glasses for the computer, and I've got a special pair of glasses that I can use for reading in that specific case. I even start having problems driving longer routes.

In other words, I have ~~really~~ rather (I can still most tasks, just with a headache) bad eyesight during winter and spring, but usually have much better eyesight and barely need glasses during summer and fall.