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Comment by Aunche | Hacker News Reader

Needing a prescription for glasses is a bit absurd to begin with. The worst case of wearing the wrong prescription is that you'll get a headache. I suppose it could be a bit dangerous if some drivers were slightly disoriented, but I can't imagine glasses being more dangerous than something like Tylenol.

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I... can't form a coherent response. How do you even know which prescription to get? Do you have astigmatism? How do you measure that?

It's not a scam. It's just overpriced in the US, because they can't get their stuff together in the health department.

If I need a new pair of glasses with the same prescription I have now (Say, for example, I fall and break my glasses), I shouldn't be required to go get examined to get a new pair simply because it has been more than a year. I want the same thing I've been wearing, and the worst possible outcome from me getting them is that (if my prescription has worsened, which it hasn't in 4+ years) I can't see quite as clearly at long range as I ought to.

That would be weird, good thing you are not required to get examined in order to buy glasses. I don't know why you think you are required.

You are required to get a new prescription because your original prescription expired.

It's by state.

Not for contact lenses (16 CFR 315.5):

https://www.law.cornell.edu/cfr/text/16/315.5

That doesn't make much sense because adult vision doesn't change much. It should be perfectly valid to use an old prescription unless you want to re-check your vision. I've never seen this law in Asia or Europe and people are living just fine.

I just had an eye test and both of my eyes had changed enough after two years to make a very noticable difference to my prescription.

You don't technically need an Rx. You can go to Zenni and just start plugging in numbers if you want. I'm not sure what that gains you, though.

It gains you the ability to replace a broken pair of glasses for just the cost of the glasses, rather than also having to pay for another eye exam.

> The worst case of wearing the wrong prescription is that you'll get a headache.

Doesn't using the wrong prescription worsen eyesight faster?

At least, it's been my general experience that when a child is curious about people's glasses and is given the glasses so they can experience the effect, they only let them try it for a couple seconds and are explained that using them for too long can cause damage to their eyesight (because it's the wrong prescription for them who have perfect eyesight). Is that a myth?

The real reason is they don't want grubby hands smudging up their glasses :)

No... It's not like I've seen it only once or never talked about it with other people. It's general common sense or a common belief, even if it turns out to be false.

The eyes don't care about what's in front of it. The brain does the image processing, so that's the only thing that's affected by a bad prescription. If your glasses are so wrong that it causes eye strain, it may cause damage, but you'd have to purposefully put yourself into that ordeal.

https://mayoclinichealthsystem.org/locations/la-crosse/servi...

The eye very much does care what's in front of it. Look up "emmetropization".

Try a web search for neuroplasticity.

Yes, it's a myth in the sense that you would need to wear the glasses several orders of magnitude longer and/or consistently for there to be any negative effects. Some people seem to think that even looking through the glasses will unleash demons into the healthy eye.

Modern research does point in the direction of the eye remodelling itself based on what kind of input you give it on a longer scale, though. This includes the amount of light seen during the day and whether it is able to focus rays or not. There are indications these play a role in the development of myopia.

Plus wearing glasses with a slightly different power than your own is infinitely safer than not wearing them at all.

Tylenol (acetaminophen) is probably a pretty good example. They both seem pretty safe in reasonable situations (a slight difference in prescription value, a couple hundred extra MG dose) but can be hugely problematic at greater levels (lethal/permanent liver damage or completely unable to see anything with a terrible prescription)

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