Interesting observation Cattletruck. Many years ago in my forties I noticed that my distant vision was beginning to degrade. I was spending a lot of time in front of the computer and I guess I was straining my eyes without realizing it. I eventually went for an eye test and was given a prescription for bifocals. At my annual medical the doc confirmed that I was only just passing the distant vision requirement. The distant correction was quite weak and consequently I rarely used the bifocals but I did buy some cheap reading glasses. I then always used the reading glasses when in front of the computer and of course for reading. At my next annual the doc was quite surprised when he found my distant vision had improved considerably. Obviously, straining to read had started to permanently deform my eye lenses and it wasn't until they were able to relax that my distant vision returned. Of course that was many years ago and I now need glasses for both near and distant. I use bifocals but that's just my preference.