First, I’m not sure what harm could be caused by someone wearing the “wrong” prescription of glasses or contacts, so I’ve never really understood why I need to go to a doctor to correct my myopia (yes, they check for other things, I get it, but we’ve pretty much established I don’t have astigmatism, glaucoma, etc., I just want to be able to switch to a different strength if my nearsightedness gets worse, or not have to go to the doctor when I switch my online contact lens vendor). It would seem that most people would quickly figure out if they had the wrong magnitude of correction by trying on multiple models.
Okay, and the optical industry lets them do that – but only for the farsighted + corrections. How is trial and error fitting of a nearsighted/- correction medically or risk-wise any different? Why have optical prescriptions at all, but more specifically, why only in one direction?