It kind of had to happen, I guess. I now have glasses!
There wasn’t anything majorly wrong, I have an astigmatism which I think means that my cornea is more like a football than a disc, and now things that I never really noticed were blurry, are actually really sharp.
Another thing the optometrist said is that I might have less trouble differentiating between what is almost a square and a true square, which might explain why I sometimes have trouble working out if a screen resolution is the correct aspect ratio for a particular screen.