This morning everything is back to 'normal' = glasses are again needed to provide clear distance vision!
I was feeling a bit 'weird' yesterday, in addition to the reverse eyesight thing. Hope to speak to a GP later.
I would suspect a blood sugar issue in that case, they can be quite transient. You may be prediabetic (quite a lot of people are) and this is worth checking out. If this is the case, prediabetes doesn't mean that you will develop diabetes but rather that you have a raised probability of doing so, and there are things you can do to avoid it.
However there are other possible causes, and raised intraocular pressure is one of them. So it is worth going to an optiometrist and having your eyes tested. One word of caution with the IOP test: you should also have your corneal thickness measured as an unusually thick or thin cornea can distort the result. Not many optometrists do this yet.