I have a very weird situation where my right eye was fine but my left, for reasons unknown, has a thicker lens. This can be happen with cataracts but I'm just under 50 and have zero clouding. The eye doctor said it's not myopia in the "usual" sense but the end result is the same: myopia prescription lens.

Thing is, I ignored it for about 10 years and my brain simply ignored whatever signal was coming from that eye. I'd look at things and see no blurring unless I closed my right eye. However, at a certain crossover distance my brain "switches over" because my left eye has amazing close vision and my right eye doesn't. I can actually feel it when this happens, like a physical sensation. No headaches, but it is "odd".

Anyway, I decided to get glasses, and it turns out I need two different prescriptions. One is close up (not longsightedness, it is still a myopia lens). The other is for 1m-∞