Though they don't, in my experience, ask for any indication that this comes from a prescription, that it's up to date, etc. You're free to use numbers from an ancient prescription, just guess at your refraction, whatever.
Some other online glasses sales places will make you show them a sufficiently-recent prescription.
Any store will sell me clothes that don't fit, food I'm allergic to, and chemicals that are dangerous if used incorrectly. It's not unreasonable to expect the buyer to take some basic responsibility.
They have their limits to this laissez fair policy though, for whatever reason...I tried buying multiple pairs of glasses at slightly different strengths from Zenni (stronger rx for it for outdoor distance views and weaker for inside and they freaked out and they called and asked if it was a mistake. When I explained what I was doing, they said nope and cancelled the order on me.
And toothbrushes too, did you know in some countries it is legal to brush your teeth and buy a toothbrush even if you didn’t see a dentist in the last year?
I'd love to see some facts backing this up. It might be true that wearing slightly off prescriptions could train eyes slightly worse over time, but for most people going without them is a far worse option.
Also, the skillset required to prescribe glasses and contacts is something that can be (and is in some countries) effectively on the job training, not necessarily something that requires a specialist doctor with years of education. In most of Europe your average glasses shop can put you in a machine for a few minutes, and spit out an accurate prescription.
Medical regulations exist for the good of the public, and I wouldn’t risk treating a condition that a medical professional’s diagnosis is required for. The FDA would only block self-treatment if it were dangerous.
