Item — HN Reader

Fascinating hacker story in an unexpected domain. Thank you!

A side note about "getting your numbers"... The author remarks, "she’s not happy to share the measurements with me as she fears I’ll run off and get my glasses made online".

This will obviously vary by jurisdiction but what the author describes may be illegal in some places. e.g. where I live, there is a law since 2010 requiring opticians and optometrists "to give clients, free of charge, a copy of their prescription, sight-test assessment or contact-lens specifications — whether or not it is requested by the client — and also to give a copy, free of charge, to a third-party eyewear seller or other person if requested by the client"[1]

[1] https://www.cbc.ca/news/canada/british-columbia/b-c-changes-...

8 comments

Not sure about legality but here in the UK you will find opticians will give you your prescription, but often exclude the pupil distance measurement (I think) which a lot of the online stores require.

I think you can ask for it, but they will only give it begrudgingly.

That's cause PD is measured by the optician separately when you're ordering your glasses, not by the optometrist or opthalmologist who writes the prescription.

In other words, it's not part of the prescription, it's instead part of the glasses fitting process.

A non-eye related example would be if your doctor prescribed you a brace and the person at the medical supply store measured you to find out which size you need.

...and can be measured at home using a ruler and a mirror, pretty simply. Close one eye, align the ruler at 0 under that pupil. Open the other eye, close the first, read off the distance to the 2nd pupil.

Did this for my wife recently. We measured multiple times very carefully, and got it very wrong.

Another way is to look through binoculars, get them adjusted just right and then measure them. Don't try to measure center to center. Assuming the eye cups are the same measure from one side to the other (left edge of one to left edge of the other).

I measured my kids using just a ruler and they're all happy with the results. I also measured myself using a mirror, ruler, and a phone camera (so the measurement couldn't be skewed by eye movement) and my results also turned out great. However, I can understand why it would be easy to measure incorrectly, since the ruler is never very close to the eyes.

I have done this a few times, and got inconsistent results. Distance to mirror, or camera to face, positioning of the ruler, they all seem to induce variability. Once I got a reproducible result and went with that, ordered progressive glasses online and they were… off. On another occasion I got PD (and prescription) numbers from optometrist at Visionworks, then took numbers and ordered from Zenni, and they were… off again. Also this PD number again different from the one I had measured myself. But when ordering directly at the store they were perfect. I even wondered whether they actually gave me the wrong PD number, to "teach" me a lesson not to go order elsewhere. Sigh.

Maybe use a mirror, ruler and a camera?

Ed: i see @andai made a similar comment.

Might indeed be better to use a "long" object to indicate pixel length by division (credit card is 5432 px = 5 cm) rather than going by a ruler which might typically only be accurate to 0.5mm at best anyway.

There's no reason for them to not give it, as it's an easy item to address.

In the US, the person who takes your pupil distance (PD) usually isn't the person who writes your prescription. One is a doctor and the other a technician.

When you go to an optician, the doctor takes you in the back and determines your prescription. Then you go out front to the showroom and pick out your frames. There is usually a technician out there who will take the PD measurement and combine it with the prescription, and frame and lens selection to make your order. The technician is also the person who fits you with the new glasses when they arrive.

I recently (in US) asked for it, and was given a hand written sticky, begrudgingly after asking why you need it. But once asked again, no further objection.

Your PD isn’t part of the prescription. But the prescription itself must be provided to you by law in the US.

For anyone near a Warby Parker, they'll happily measure your PD in about 30 seconds. Measurements can vary slightly so you might want to do it a few times and average them.

You can also do it online with Warby Parker as long as you have a credit card (to hold under your face; not to pay with).

The PD also varies a bit from reading glasses to distance glasses. If you are ordering single vision glasses, you might want to collect both numbers.

Weird. I’m in Mississippi, of all places, and, without asking, my optometrist always sends me off with a printout containing my prescription and PD.

Inter-pupillary distance is among the few things glasses related that can be measured yourself.

That may take some practice. I did it myself once, and was off by about 4 mm. The resulting glasses were incredibly painful. My eyes would try to look in two slightly different directions, and my brain would put the wrong 3D picture together. Whenever I moved my head my eyes would readjust, which took a noticeable period of time, and I could literally feel my non-dominant eye turning itself to find the focus. I chucked the glasses after a few days.

I'm sure it could be done better, but boy, that was an interesting experience I hope to never repeat.

When I bought online from Zenni optical they sent a plastic ruler that you set on the bridge of your nose with a slot in the middle, and can be used to measure PD. It's similar to this: https://store.eyeque.com/eyeque-pd-ruler.html

Thanks for the tip. That would be way easier than doing it with a plastic school ruler.

It's a little hard to measure it by yourself but with a friend it's easy. Just make sure your looking far off into the distance and not at the persons face who is taking the measurement.

I found that the best way to get a nice, precise measurement was to take two pieces of sticky note and punch a hole in them with a pin. Put them on an existing pair of glasses and line up a distant (unless you're getting reading glasses) sharp corner with the pinhole over one eye. Switch to the other eye and see if the pinhole is lined up—if not, adjust the pinhole positioning and try again. Once the pinholes are aligned, you can measure the distance between them.

Much easier than trying to get someone to measure it accurately with a ruler in front of your face, or trying to draw dots with a washable pen in front of your eyes on old glasses, or any of the other methods I tried. The measurement I took appears to be accurate (the glasses I ordered from Zenni using it are comfortable to wear), and it was easy to get a precise and repeatable measurement to within about half a millimeter.

I encountered this in Canada, with an explanation given to me that there was a lawsuit at some point where an optometrist was sued after a client ordered glasses elsewhere based on the provided IPD and got glasses that caused headaches or something like that.

From Wikipedia[1]:

> In both the UK and most of Canada (excluding British Columbia[5]), the PD measurement is classed as a dispensing tool rather than a part of the actual prescription of the person whose eyes were tested, thus there is no obligation for a PD to be provided on patient request.

[1] https://en.wikipedia.org/wiki/Pupillary_distance

As part of GDPR you can request a copy of any personal data. In the UK this is governed by the ICO, and it’s called Right of Access.

https://ico.org.uk/for-organisations/guide-to-data-protectio...

You get your PD measured at the time you order your glasses. If you never order glasses they'll never measure your PD.

Are you assuming they keep records on the PD measurements of clients who didn't actually purchase glasses there? At least at the opticians I've used, I don't think they do.

This did strike me as strange. Imagine going to a doctor getting a blood test and being told your numbers are good or bad but the doctor refusing to give you the actual result. They are your results, you paid for them and are part of an overall need to understand your health.

> you paid for them

most places that sell glasses do those for free tho. I agree they should be given out and they do in europe, or at least in the two states I lived, but being paid for is not the angle to come at it from

I don't think I've ever had a free exam in Ontario— my insurance covers one (up to like $200 or something) every two years, so that's about the cadence I get them on.

So it's a paid-for thing; I don't feel bad about taking the prescription and buying glasses online. That said, the glasses from the shop last way, way longer than the online ones, so I really just use online for sunglasses or like to get novelty frames for a costume or something.

I'm in Ontario, too, and couldn't get my PD from Laurier Optical. So I left, went on Amazon, and bought a PD Distance Measurer for a couple of hundred bucks. Did my whole family, and now my wife feels better about ordering from Zeni. Saved enough on a single pair of glasses to pay for the meter.

"Free" exams aren't free, the cost is included in the frames purchase. You can pay for an eye exam and walk out with a prescription, you just have to explain your intent.

Not always. My place doesn't do it.

I don't know about the US (I thought HIPAA was very comprehensive...?) but in the UK you are legally entitled to view personal data about yourself. It wouldn't matter if you paid for the test or not, if it's on file you should be able to access it.

I think a more apt analogy is that the doctor gave you your blood test results (just as they'll give you your prescription without the PD), but refused to characterize the color "A deep shade of crimson with a touch of scarlet", which is something that you can do yourself with a little knowledge.

So you're still getting the information that requires special training or licensing, and you can get the other information yourself if you really want it.

I actually read up on the local legalese around this (for Switzerland), and it turns out that doctors can refuse to share information with the patient if they consider it unhelpful/dangerous to do so, but have to share it with other medical staff should they request it.

Especially in the context of psychotherapy or when using placebos, this makes a lot of sense.

I found it fascinating, after moving to Finland and having an MRI scan done, that it was possible to order a copy of the results on CD-ROM posted to my house.

Having worked in the medical field in the past exploring a DICOM dataset was no challenge, and the end result is I have a rotating 3D-view of my own brain! (Well just blood vessels, but still ..)

Here in the US, I got an MRI at a 3rd party lab (not a hospital), and they gave me a copy on CD-ROM as I walked out. I didn't even have to ask! I was quite surprised, as I assumed the results would just be shared with my doctor electronically. I have no idea if I would have gotten this same treatment if I had paid 10x as much for the MRI at Stanford Hospital. (I'm guessing not).

Right, except that the test at a optician is often free (in Germany at least).

A couple of years ago I had my vision test done (in Texas) and at the end I asked for my prescription. The PD measurement wasn't on there so I asked for it and was told that is measurement is taken when I buy glasses. I offered the person $20 to just do the measurement and give me the number and they wouldn't do it.

If you go to an eye doctor they will give it to you. At least in German

I was going to pipe in and say the same thing. I'm a few provinces east of you.

I've heard the same thing about hearing aid prescriptions, CT (and similar) scans, and blood test results. In Canada they'll happily give you the results for your own records, but apparently some other countries don't provide it as a general right, leaving businesses to decide whether they want their competitors to be able to pick up work they initiated.

I think the difference is whether medical is private or public.

In Italy I've got the measurements since 30 years and counting.

I imagine the healthcare system plays against you in your country

The optometrist at my local Vogue Optical is actually only affiliated by location. She was happy to give me my PD as she doesn't sell glasses anyway. I'm sure most people walk out of her office into the Vogue Optical show floor and buy their glasses there.

That is true in the US also. https://www.ftc.gov/tips-advice/business-center/guidance/com...

That may be, but for glasses at least a key measurement is pupillary distance, and it is like pulling teeth to get them to give you this. At my most recent encounter with an optometrist - where I had already selected and was in the process of purchasing from them glasses that cost me hundreds of dollars after my insurance discount - I had to ask them no less then four times to write down my PD so I could buy a few pairs of beaters online. They kept "forgetting."

I presume the PD doesn't change after you are an adult so you could reuse it in the future.

My real concern is if I encounter some problems, if I got the exam and glasses from one place, I can insist they fix it for me instead of arguing who is at fault.

I'd treat a refusal to share the prescription as a dealbreaker. I've never encountered it at all. I'm sure it DOES happen, but if you're very clear about your expectations you can keep them from playing this card.

In the EU, a GDPR data subject request will get you all the data you want.

Correct. And in the UK (maybe in other countries too) you can make a request verbally or in writing. So if they write it down; your allowed a copy.