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Making My Own Glasses (eidel.io)
629 points by olieidel on Oct 4, 2019 | hide | past | favorite | 187 comments

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-...

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.

Did it for myself. Ordered online. Best glasses yet (I think mainly thanks to a my very patient optometrist.)

I measured by taking a picture of my face with a credit card for reference and measuring the pixels with the measuring tool in GIMP. (These were the actual instructions on the website I ordered my glasses from.)

Also worth mentioning I paid $40 ordering them online, in the article it says he paid $280!

May I ask you where you ordered them?

Edit: Just found out they ship worldwide for €3.


I was amazed because until a friend told me about this site, I've been paying hundreds of euros just for the frames! At such a low cost, I could even order slight variations on the strength.

They have a lot of options for better lens material, have it darken in sunlight, anti glare coating etc, but I just got the cheapest one and it was fine.

I found that it's easier to do it yourself than have someone else do it -- my wife and I measured mine, hers was off from mine by 6mm (2mm on one side, 4mm on the other, I have no idea how she was nearly half a centimeter off, maybe my eye moved), I ended up going to an optician a few months later, and my measurement was exactly the same as what they measured with some device.

Don't see how you can possibly do it for anyone else, using the mirror method, without getting 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.

Progressive lenses need much more accuracy to be fitted correctly. This means a mono-PD (separate PD for each eye, not just the distance PD halved) and also a height, usually from "datum" measured for each eye too. This measurement would be different depending on the frame and how it sits/adjusted to your face.

This means the frame must be chosen and fitted to you before any of these are measured.

It becomes a 2D measurement.

There is a lot more to it (vertex distance, pantoscopic tilt etc) but the above is the absolute minimum.

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).

do they also need the picture of the backside and home zipcode?

if not, sounds like a startup idea.

Now that is a clever way of doing it!

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.


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.

Doesn't do what?

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).

You do. We got MRIs on disc at UCLA Santa Monica, free of charge. It's pretty standard.

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 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.

He probably saw the first result incorrectly, opticians almost exclusively use negative cylinders, it seems incredibly unlikely that he would both stumble upon a rare exception using positive cylinders, and that she'd coincidentally get his astigmatism way wrong as well.

I share his, uhm, perfectionism regarding optical corrections, and it's led to quite some anxiety. I feel like eye exams here aren't done with a lot of care, and that they just aim for "good enough". I'm not sure what to do with the knowledge that you can buy such an optician kit and test yourself. It's either a great or an absolutely terrible idea.

Some good thoughts. Totally agree with all your points.

Everytime I read about glasses I have to think about the Luxottica-Monopoly which kind of controls most of the market and prices of glasses/lenses.


It is pretty easy to get non-Luxottica frames.

Not too surprisingly, independent small batch production runs of frames end up costing a lot of money.

There are also artisan frame makers who hand make the frames. If you are going to pay $300 for some frames, mine as well get an actual work of craftsmanship.

At the end of the day, most Luxottica frames are actually far cheaper than the high end independent frames you can buy. Exceptions are the fancy branded frames, but at that point the $ is for the Gucci logo.

Online bare bones frames also exist, or just go to Costco.

A 3x-4x markup at retail is normal. For low traffic businesses, an even higher markup is needed to stay in business.

Those online stores do a lot of volume, and don't have to pay leases or for nearly as many opticians to be on staff.

> that the prices we pay for eyewear in no way reflect the actual cost of making frames and lenses.

Of course it doesn't. The price we pay for eyewear is the price we value it at. Just like literally everything else that is sold in stores that isn't a commodity good.

Doesn't help that insurance is involved. $200 a year eyeglasses allowance. Eyeglasses end up costing $200. Is anyone surprised?

Yeah, I buy Bellinger Blac carbon-fiber frames. Hand-made in Denmark. Not cheap, but as a guy, it's about the only accessory I own.

My view is that if you're using it every day it's worth spending extra money on it for the best.

This is how I excuse spending $250 on a mech keyboard and using high-end smartphones/laptops.

Not buying super expensive new cars, or any cars, is probably the best place to not do this. Unless you commute daily.

ok, how can i acquire this?

Find a local retailer using their website.

In reality, it's pretty hard, because very few stores have much selection at all to look at. After a number of years of buying their frames every once in awhile, I found an optometrist who invited me to "meet the sales rep" so I jumped at the chance; turned out it was a co-owner and also a model for the company's materials, he brought basically every frame they owned to the meeting, told me great stories, made great recommendations. It was the amazing experience I had been looking for but not finding. Just gotta get lucky, I guess, with smaller companies.

it turns out a different eyeglasses place in the same mall as my current one sells them. huh, easy enough.

I remembered this as well. This bothers me, as I just had to get a new set and they are ridiculously expensive. I originally opened the article hoping that this was some kind of "I 3d printed my own frames" or something to that effect. I am hoping someone will figure out how to disrupt this industry.

Zenni Optical [1], EyeBuyDirect [2], VisionPros[3] among others let you buy online as long as you know the numbers.

[1] https://www.zennioptical.com/

[2] https://www.eyebuydirect.com/

[3] https://www.visionpros.com/

I was hoping for the same. Still an interesting enough read to keep me until the end, though.

Agreed and I wish this was exposed more, so people might spend their cash or insurance credits on alternatives that can be more innovative and cheaper.

I supported Frameri through their crowdfunding and beyond for this reason. I bought several sets of interchangeable frames and lenses from them and am pretty satisfied. But then they closed up shop and left me hanging with a never-fulfilled final order. :-(

Yeah, I was surprised that he bought his final pair of glasses online for such a high price. Maybe the frames were expensive? I've used zenni optical for many pairs of glasses, and they're much cheaper.

When you have a prescription that strong the lenses get expensive quick. Even from Coastal.com I end up paying $200+ for high-index photochromatic lenses, because my left eye is -4.75.

The article mentions a +7 in one eye, we’re in the 1.67 index range (mine are 1.6) with a script like that. €208 is a deal.

I just checked with zenni optical, and with his prescription it did recommend the 1.67 lenses. The total was $59.

Not to say that $200 isn't a great deal compared to Luxottica, and he did say that he was very particular about his frames, but $200 still seemed high.

This is clearly a case where the sole act of him sharpening his own perception of what glases do resulted in him getting better glases.

I work freelance as a colorist and re-recording mixer – both are professions which are highly based on perception. And it is certainly true: if you try to really go into the details of something, be it color, sound or anything else, it already helps a lot if you sharpen your senses to these things. I always say: you don't pay me for beeing able to use some software, you pay me for having developed my senses over years in a way that others didn't.

Totally agree. It's a cool idea that going very deep in a certain field yields benefits which were unimaginable in the beginning (or to others).

For more than 10 years I am going to the same optician for glasses. As a sport pilot, I need to have 2 pairs at all times (one is kept as reserve in the cockpit); changing one to another, with identical "everything", produces a serious discomfort that I cannot explain. I learned to live with the idea that eye sight is complicated.

Measurements at different points in time can differ slightly: in the morning just after I wake up I get some values, after staring at this monitor for 12 hours I get slightly different results. I always make the glasses from the morning measurement, but luckily the values rarely differ from one year to another (I change the lenses every year on the pair I wear on the motorcycle, riding with the visor up I get the lenses scratched in about one year from the dust in the air).

> Measurements at different points in time can differ slightly...

Indeed! The best thing you can do before an eye exam is be rested, eat an apple, don't stare at your phone in the waiting room, look out the window if there is one.

Tired eyes will give differing results. Low (or high) blood sugar (even in healthy people) with give differing results. Straining your eyes by looking at a screen in the waiting area can give differing results.

Note for all these I say can and not do.

I suspect the discomfort when switching glasses is that the inter-ocular distance is different between the two glasses (one is likely right or "more right"). You have the right correction, but it is off-axis WRT your pupils with one pair.

When I go to my $$$ optician, the technician marks my pupils on the blanks in the frame that I've selected using a sharpie (before the glasses are made) and adds the inter-ocular measurement to the glasses information. When I put on the resulting glasses, I don't have any eye strain symptoms and my vision is good (instantly).

When I went to cheap storefront glasses places (I don't do that any more) and I put on the resulting glasses, I get a "stress" signal from my eyes and then they adjust to work with the suboptimal glasses but the eye strain is always there.

My optician friend is doing the inter-ocular distance right, he showed me the process while he was cutting the lenses on a high-end computerized machine. But the only difference between my glasses are the frames, there are some differences in the frames that makes a difference in the final product. I guess it is the angle between the lenses, even a small difference can be creating the discomfort. It takes me a few hours to adjust.

Interesting! For what it's worth, I also learnt that there are quite a few lens manufacturers out there and they all differ slightly regarding lens thickness and refraction properties. That may be another explanation.

And, if your optician is close by and shares your belief that your values vary over time, getting your values checked in different "states" (morning / evening / tired / etc.) can be helpful for deciding on what the "right" values for your glasses may be.

Slightly different pupillary distance I would bet.

Misleading title. He tested his own eyesight and ordered glasses online. He didn't make his own glasses.

Still an interesting read, just not what I expected from the title and lead.

Eh... he provided custom specifications to a manufacturer.

Apple makes it's own SoCs for the iPhone, only Apple can't make semiconductors. They provide specifications to a manufacturer. Apple makes the iPhone, except it's Foxconn that manufacturers it.

The APU in the Xbox One is made by Microsoft, but it's composed primarily of off the shelf designed CPU and GPU cores from AMD and manufactured by TSMC/GF/<insert foundary>.

The whole blog post was about measuring eyesight, not about what it takes to actually make glasses.

My natural expectation was that the author made his/her own lenses and fitted them into a frame. Or designed their own frame, ordered the parts and then assembled them into a frame. I was expecting a technical rundown about all the steps it took to do something like that.

The blog post is still a fun read, but the title is definitely misleading.

By this logic, I am “making” my own pizza every time I tell Dominos to make me a 20cm pizza with cheese and sauce. I am “making” an IKA sofa when I order it online, telling the manufacturer the model, the size (2 seat, 3, etc).

No, what the OP did was check/confirm his numbers and then bought a pair of glasses from a website. Many people buy them from websites, typing in the numbers they received from their doctor. None of these people are “making” anything.

I don't disagree with you, and the line between ordering and making is fuzzy.

Your examples of an Ikea Sofa and Pizza are great examples of either end of the spectrum. An Ikea sofa has finite configurations that could all be permuted into model numbers, the parts are interchangeable and swapped between models, and prefabricated. A pizza however is completely made to order on demand and if there's a mistake the components are nonrecoverable waste.

With Apple's custom SoC, they're designing a custom circuit however that specification is sent to someone else to manufacture. At it's core, it's not unlike ordering a pizza of astronomically greater complexity. So what makes a custom pizza just an order and not a make? Is it the relative simplicity/complexity of the task?

If I enlist a factory in China to manufacture custom mouse pads based on my exact specifications, did I make a mouse pad or just order it? Does it matter if the mouse pads are just press cut fabric backed neoprene in various colors and shapes?

Glasses are somewhere between an Ikea Sofa and a Pizza in terms of modularity. The lenses and frames are off the shelf but once cut the lenses are spent if an error is made. Glasses however have much more exacting specifications than a pizza or a Sofa.

It's not completely without precedent to speak that way. "Build" and "make" are different words, but it is common to say "we built our own house" to mean that you had one custom built for you. Also, you can go on almost any car manufacturer's web site and they let you "build" a car, which means selection options and packages to see what it costs and start the process of ordering.

> As a doctor I know some things about the human eye so I understand how to use those lenses. However, I have no clue about the magic ritual of the optician (“Do you see better with this lens?” - selects random lens and holds it in front of my eye).

>Luckily, I didn’t have to.

There's a specific reason why they do this and ask you to make a decision in an instant. It's called accommodation. Your eyes will quickly try and accommodate and find focus if they're allowed to stare too long. This could explain the reason he got such different results from the exams. He was trying too hard. Just follow directions.


> One more thing. Do you remember the process in which an optician makes you wear a new pair of glasses and stares at you with this optician-look, takes the pair of glasses away from you again, goes to the back office and starts bending parts of it in a seemingly random manner, comes back, hands you the pair of glasses which now suddenly fit perfectly?

> Yeah, I attempted to do that with my new pair of glasses and noticed that I suck at it. I would bend it to look similar like the glasses from the optician only to realize that the back of my ears were hurting after a few hours of wear.

Is he really a Doctor??? He doesn't know there's a Mastoid bone there that the "bending" (aka: Adjusting) the optician is doing is to AVOID putting pressure on that bone!?

Yes, I am a doctor. As far as I remember, I studied medicine and graduated.

As other comments point out, medicine is a very specialized field nowadays and I didn't specialize in any field (I got into coding healthcare software instead) - in Germany you study all disciplines at University (min. 6 years) and then specialize during something comparable to US residency in a hospital.

I understand the process of accommodation. This poses the risk of e.g. over-correcting short-sightedness if you're not aware of it because, with each lens of increasing strength, you accommodate and think "geez, everything just got sharper.. again!". I was aware of this and, as you can find in my article, actually ended up using very similar values for dioptries (the spheres) as the opticians. So either all of us totally forgot about accommodation or all of us were aware of it :)

My values mainly differed regarding to astigmatism, and accommodation doesn't play a significant role there.

I am also aware of the bone behind my ears, thanks for reminding me :)

While you do learn a lot of stuff in med school, learning how to bend those things of glasses which go behind your ears is not part of that. I suppose that's not a skill which can be taught well, anyway - it's more like craftsmanship, getting it right by having done it lots of times.

Eye surgeon here.

Good job and interesting story!

As a side note: for optical reasons, the spherical equivalent of the lens (which will determine if you are overcorrecting or not) is calculated by adding the sphere value + half the cylinder value (whatever the axis value).

You ended with a correct prescription as far as I can tell by looking at the different measurements , however you did not totally grasped the optical subtleties of the accomodation process : astigmatism is important (a small overcorrection is not a big deal anyway)

It is usual to undercorrect the cylinder values given by the autoref and your ophthalmologist would have given you the right prescription I think.

I'm just saying that to underline that as I doctor myself, I'm usually very wary at thinking that I can fully understand, in a few days, what my colleagues do. I'm totally into the hacking spirit but let's stay careful, especially for more dangerous things than glasses.

Well FYI, cyl is generally converted into minus cyl, the axis flips 180. So your first two measurements of cyl are close together.

Also cyl/sphere differential is also hard to determine but often follows a pattern in that you can overcompensate in sphere for cyl and vice versa.

Not even going to begin to go into the effects of possible tolerance differential, prism imbalance, and that is just with Single Vision Lenses.

Also you generally have 90 days as industry standard to go back and retest your RX.

If I may, particularly as a doctor yourself, you should call the eye doctor "ophthalmologist", as you surely know if you use "part of the body + doctor" there might be issues should you report a visit by a "proctologist" ...

It sounds like the author studied medicine in German.

In German, "ophthalmologist" is "Augenarzt", which is literally "eye doctor" (Auge: "eye" + Ärztin: "doctor").

Why replace a good, short and clear word with a bad and long word that adds no information, but fewer people will understand? [Edit: I think I'm wrong about the adding no information, depending on country there might be other types of eye doctors than ophthalmologists]

Come on, it was only a (good?) old joke ...

Haha! Good point. I guess I thought "eye doctor" made for easier reading, assuming not everyone knows that ophthalmologist == eye doctor.

The way I typically like to use terms of art in writing is to write the term out first, and then a parenthetical with a definition. For example here you went to see an ophthalmologist (eye doctor). It's also good for acronyms and initialisms.

> Yes, I am a doctor. As far as I remember, I studied medicine and graduated.

Well, that's settled, then. ;)

> I understand the process of accommodation. This poses the risk of e.g. over-correcting short-sightedness if you're not aware of it because, with each lens of increasing strength, you accommodate and think "geez, everything just got sharper.. again!". I was aware of this and, as you can find in my article, actually ended up using very similar values for dioptries (the spheres) as the opticians. So either all of us totally forgot about accommodation or all of us were aware of it :)

Well, minus does like more minus. (Ask your new optician friends).

> My values mainly differed regarding to astigmatism, and accommodation doesn't play a significant role there.

No, but squinting, even a small amount, does. If your axis favors it.

> I am also aware of the bone behind my ears, thanks for reminding me :)

You're welcome.

> While you do learn a lot of stuff in med school, learning how to bend those things of glasses which go behind your ears is not part of that. I suppose that's not a skill which can be taught well, anyway - it's more like craftsmanship, getting it right by having done it lots of times.

Indeed. That's why there are professionals who do it. If you are still going to do it at home and you have a plastic frame, heat the ends up slightly. You can microwave a damp rag and wrap it around the ends for a moment. Or use a hair dryer carefully. At the optician's office, they have a hot air blower that does it. Used to be they had glass beads, but those got in between lenses and caused no end to trouble. If you bend cold tips, they can more easily break.

I apologize for questioning your credentials. I guess I was a bit harsh. I just feel the article came off mostly of a slight arrogance with only a smattering of humility. You seemed to think that you could make up for years of working in the industry with only a few days of playing around. That being said, congratulations on being mostly successful. However, I am sure I don't have to tell you that an eye exam is only partially to refract you. There are other health issues that can be detected by having a routine eye exam.

> Is he really a Doctor??? He doesn't know there's a Mastoid bone there that the "bending" (aka: Adjusting) the optician is doing is to AVOID putting pressure on that bone!?

Doctors are pretty specialized today, and he has a list of publications on his site, right in front of you, so that may be an excessive reaction.

> Is he really a Doctor??? He doesn't know there's a Mastoid bone there that the "bending" (aka: Adjusting) the optician is doing is to AVOID putting pressure on that bone!?

I think that's a little harsh. I took it to mean he realized he had no idea how to properly bend it, and pointed out an optician is the expert here.

> There's a specific reason why they do this and ask you to make a decision in an instant. It's called accommodation.

You are right. It can be an issue in the other direction though.

People are checked after often sizeable waits looking at the same thing (their phone, the wall, outside) for a long time.

When you then start the switching lens tests, there will be a set of lens optimal for your current situation, and a different set of lens that would fit better for a long day of doing whatever you are usually doing with the glasses on.

Knowing how good a pair matches after accommodation is equally valuable, IMO.

It's important to only do eye tests when you are tired, so you get lenses that help you when you need them.

Sorry, that's bollocks if not outright dangerous advice. You always need glasses... and having wrongly spec'd glasses will induce massive stress on your eyes and brain.

Please consult with a medical professional.

But you do have to choose specifically _when_ you consult with that medical professional. Late in the afternoon after a day in front of the computer, when your eyes are tired? Or first thing in the morning when they're fresh?

There is a big difference between farsightedness and shortsightedness. Optometrists can use eye drops that prevent accommodation for farsighted patients, or they can detect the "plateau" in good vision and take that into consideration for the prescription. No need to wait until your eyes are no longer "fresh" unless you have a really bad optometrist.

> There's a specific reason why they do this and ask you to make a decision in an instant. It's called accommodation. Your eyes will quickly try and accommodate and find focus if they're allowed to stare too long. This could explain the reason he got such different results from the exams. He was trying too hard. Just follow directions.

I don't have a long experience with glasses but I have never received these instructions and my experience is similar to the author.

This article found 13 out of 30 opticians were off by a significant amount (poor or very poor): https://www.huffingtonpost.co.uk/entry/high-street-opticians...

I had great glasses for about 25 years. Then my eye doctor retired. Over the next couple years the first couple pairs I received from the same location's new doctors were bad enough to cause me to return them. The third has been marginally acceptable. It's a real shame when talent retires.

I had someone recently quit my team for a way better opportunity that my company couldn't provide.

More or less jokingly we showed up with chains on the last day to bind him to the desk :) we allowed him to part after a couple of beers though.

Yes its super painful to lose talent.

As a life long glasses wearer I don't really agree there's a problem with the "better or worse" method. It's a pretty interesting implementation of bisection search and it's a very controlled environment. It's also a great example of how constraints (time) helps you arrive at a good answer without over thinking it.

If you were out wandering the streets or looking at random things with no constraints you would be overwhelmed with choice and it would be very hard to draw a conclusion. You may decide what's right is based on looking at something, only to find out after all of that something else 4 days later looks way off because you didn't see that during your real world test. You end up being individually burdened with making the decision instead of letting science do its thing.

The only issue I have is frames because it's very possible to get frames that are comfortable for the few minutes you try them on in the store but they end up being horrendously uncomfortable after a day or few days of usage (even after many adjustments).

I don't know how to solve that problem though because in order to wear the frames for a long test period you would need to be able to see, which means your real lenses need to be placed inside.

Title is a bit misleading and got my hopes of that this was about grinding down glass into perscription lenes. Interesting none the less.

Wonderful read. I've been wearing glasses for 40+ years...and I agree with the generally subjective nature of the exam. "better 1 or 2". "this one or that one"... etc. Is it just a bit less blurry? Or am I guessing because I want to get out of here? At my dox, they check my Rx with a machine, then the doc does the A/B testing. They know what the answer is...but they need me to validate. Then there is time... the doc has only so much time to do the A/B testing. A few hours of A/B would statistically improve the outcome. And really, fuzzy or sharp letters on a screen is not what I look at all day...show me a monitor or a book and ask me what I see. I would love to do my own testing with a box of lenses...

> Do you remember the process in which an optician makes you wear a new pair of glasses and stares at you with this optician-look, takes the pair of glasses away from you again, goes to the back office and starts bending parts of it in a seemingly random manner, comes back, hands you the pair of glasses which now suddenly fit perfectly? Yeah, I attempted to do that with my new pair of glasses and noticed that I suck at it. I would bend it to look similar like the glasses from the optician only to realize that the back of my ears were hurting after a few hours of wear. Then I would bend them differently only to have them repeatedly slip forward on my nose warranting me to push them up every few minutes. After two weeks of bending, it still fits less well than the other pair. So I guess there are some subtleties of making glasses which are not easily replaceable through an online store.

I've done this with several pairs, and the main thing is you need to heat them to get the plastic into a temperature where it will hold a new bend. I've used a hair dryer for this, though you need to be careful not to over-heat them or the plastic will blister.

You can also go into a glasses shop and ask if they can adjust them, though when I tried this they wouldn't take my money and just did it for free, which I felt bad about.

Unfortunately, lots of places will refuse to fit/bend your glasses unless you got them from their stores. It’s just easier and less of a hassle for them to have a blanket ban vs worrying about breaking the person’s glasses and being charged/sued for it.

LensCrafters will fit/adjust any/all glasses for free without any questions. Bonus: there is usually one in most malls.

I've brought probably 10 frames there multiple times over the last couple decades, only one of which I actually bought there.

Whoa, this is unexpected. I'm the author. Thanks for reading and for all your comments! Will reply to as many as possible.

> Optician: “Now with this lens, do you see better or worse?”

> O: “Honestly, I have no clue. Maybe. Maybe not? The letters look similar but different.”

[edit] Reprahsing to make it clearer:

will it be possible in the future to measure objectively?

Sort of. There's a device called an autorefractor which can get a pretty good estimate out of your refractive error. However traditional eyesight tests tend to provide better results.

I believe wavefront guided LASIK uses some kind of automatic method of determining refractive error called an aberrometer. Some ophthalmologists have a device called an i-profiler that they use as part of their assessment which appears to be an aberrometer.

Everything I've read on the matter seems to me to indicate that there is possibly some kind of hybrid automated autorefractor/aberrometer type technology that could be created to give fairly objective and accurate measurements of refractive error with no human operator, but given that legally an ophthalmologist would need to sign off the prescription anyway the upside is probably limited.

I was excited to get lasik when wavefront came out due to one eye having astigmatism. I came out with 20:15 in one eye, 20/20 in the other. Overcorrection is normally avoided, but I jumped when wavefront lasik came out. Totally worth it.

Yes. Last year, I realized I needed glasses, went through two opticians and three pairs of lenses, still wasn't happy, and finally ended up seeking out an office that could measure for free-form lenses (measured objectively with more degrees of freedom in the prescription).

This optician used Zeiss a i-Profiler to make i-Scription lenses (https://www.zeiss.com/vision-care/us/for-eye-care-profession...) They've worked better for me than any of the subjectively-measured prescriptions.

Since vision happens mostly in the brain, simply selecting a lens which focusing light at a certain point in your eye is not the only thing to optimize for. You also have to optimize for the processor behind the sensor which, at least until more advanced vision models are made, is going to be purely subjective.

Is it possible for the lens to focus light perfectly, and the brain to process that as blurrier than if the light were focused imperfectly?

I would imagine that, no matter how the brain were processing the image, the image being focused exactly on the retina is an objective truth, and that an exactly-focused image must be clearer to the brain than a blurry image.

That is true for the spherical part of the lens. When you start to look into the correction of astigmatism (done by the cylindrical component of the lens) it become a whole lot more complicated.

As others have said, yes, with limited accuracy. A big issue is the focus of your eyes is never static.

Imagine creating a lens system for a camera where you can't control for one element. That element is dynamic with a reasonable autofocus that suffers from time varying accuracy and range of performance.

We need dynamic correction. Glasses with auto/adjustable focus.

> isn't it an objective way to measure it

No it's subjective - I think that's the main point of the article.

I know, I though it might a very expensive but precise way to measure that with time or new tech could become afrodable.

I don't see why the entire process couldn't be automated. A machine could ask me "which is better A or B or are they the same?"

There are other parts of the exam that are more related to eye health, but I don't see why they vision prescription process and the eye exam have to be combined. How many people that don't wear glasses ever get their eyes examined?

"Which is better?" is the subjectivity people are hoping can be eliminated, the patient's, not the examiner's. This is an interesting black-box problem, I suppose it's possible that with the examination of enough eyes a system could suggest corrections, but I am skeptical.

> I know, I though it might a very expensive but precise way to measure that with time or new tech could become afrodable.

No it's imprecise - again that's a key point of the article. The author finds that there's a lot of variance in the measurements obtained.

Maybe it's the way I worded it, but I'm not debating the point of the author, sometimes in HN there are people that know more, or have more recent information than the authors of what is posted here.

fwiw, I talked to someone who'd done some research in that area. While using an autorefractor provides you with objective values, predicting the actual values people were most satisfied with was very difficult. Possibly because there's a lot of "post-processing" of visual signals in our brain and that may vary a lot individually.

I totally agree that having an objective way to measure this would be awesome.

I wonder if the use of a lensmeter makes you fall into a local optimum while missing out on a potential global optimum?

Let's say I go to a bad optician and get a pair of lenses that have something way off like the cylinder is the wrong way around, or toric lenses for astigmatism when you actually don't have it. Everything looks like crap but then you get used to it (the brain is amazing at adapting). Then a few years later you go get another pair, and they use the lensmeter reading as the baseline.

I think I have astigmatism, or do I? It took me more than two months until I stopped getting headaches after getting my first glasses and I could see decently. Every glasses since then are based on that first reading. Maybe I've just become used to it, and there exists a significantly better lens that I could become used to as well.

You can calculate a spherical-only prescription from an astigmatism prescription. Order cheapest-possible glasses using those lenses, and wear them for a while before visiting a new optometrist. Leave them behind before you go in, and say you lost your glasses in the ocean, or they got crushed under a truck tire, or something. If you end up with a prescription that has a cylindrical component, and it has the same axis and magnitude as your previous prescription, then you have an objectively-measured, independently-repeated astigmatism.

I'm still not sure how the whole process of choosing lenses seems to work quite well, despite being so far removed from actual day to day usage. In the ~37 years I have glasses the process only failed twice. The last time I needed to order new glasses, after wearing the glasses for a day (I know from experience that it sometimes takes time to adjust to new glasses), I returned to the store and told them that the glasses weren't good enough. To make a long story short, after going back there at least three times, and after the optometrist said something along the lines of "maybe you only think you are not seeing well with those glasses", I had to start making a ruckus till they changed both lenses.

Maybe the failure rate is low enough that it is not worth it to improve the process...

I’m glad that a good result was had, but none of these results are that surprising if you have experience in ophthalmic optics.

The initial prescription and the final one are only a little different when you consider the change of acuity they can deliver (from a physics perspective). For a script like that, the frame choice, lens design and vertical placement of the optical centres (if the frame is a little deep) could all have a similar effect on acuity.

It is also very common for there to be differences like he found between an auto-refraction and a subjective refraction.

It’s possible that they are too focused in on the prescription itself and there are issues around the lens positioning/design that are involved here as well.

I were assembling a home-optometry kit, I would use adjustable oil lenses and a laser pointer. The speckle pattern of the laser dot is affected by whether the observer is myopic or hyperopic. Adjust the oil glasses until, when moving your head, the laser speckle dots do not appear to move. If they move opposite to your head motion, make the lens diopter more negative, and if they move in the same direction, make the lens diopter less negative.

After determining exact spherical diopter, then test for astigmatism by spinning a set of parallel black lines on a white field, and parallel white lines on a black field. Or just look at a printout of an astigmatism dial chart.

I've had nothing but terrible luck getting progressive lenses for years. I'm in the -7 diopter range, so the correction has to be pretty strong. Usually the script is dead on for some part of the visual range but hardly anything else works clearly. The single vision lenses I have for computer use are right on point. I have a pretty significant astigmatism in my left (non-dominant) eye, and that one is always jacked up.

I've been going to the same ophthalmologist for several years now and over that time he's made a few mistakes in the script; twice I've had to have the glasses remade because of errors on his part. He came highly recommended, but the recommendations you get tend to be aligned with whatever hospital system you get them from, rather than true recommendations based on actual craftsmanship.

I'd be interested in figuring out how to find an ophthalmologist who uses the Zeiss i.Scription tool in combination with a subjective test. I probably need to start going first thing in the morning as well; since I have to have my eyes dilated I tend to go in the afternoons after I've been hacking code most of the day; it sounds like that could be hurting the quality of the prescriptions.

If anyone in the Detroit Metro knows of a good ophthalmologist with the Zeiss machine, do send me a note.

> she’s not happy to share the measurements with me as she fears I’ll run off and get my glasses made online (I’d never do that!).

This is ridiculous. Why should I not be given the value measurements that have just been made?

That's why I bought my own optician test lens set and now do the measurements myself. I can also test these measurements over a long period of time looking at a screen for example.

I've had people stop short of saying I should be arrested and that I'm doing something illegal.

The cost, one or two visits to the optometrist.

Because the measurement was free and provided with the assumption they're recovering the cost of equipment and labor when you purchase glasses through them.

>I needed an “optician kit” consisting of:

>Trial lenses: A large number of lenses with varying corrections

>Trial frame: A pair of glasses without lenses into which you can insert the trial lenses

>Turns out, you can order these kits online from very trustworthy Chinese resellers for around 190€.

Seems like it would be nice to have these available for rent. I would rent that for 20 euros a week, and after 10 rent-outs it has payed itself back

Why not do it?

If you want the absolute best possible correction, you also need to make sure the optical center of the lens is in the right spot. With my current frames it's a bit too low, so I need to lift my glasses a bit to make sure I see as sharp as possible, which is annoying.

It's a small effect, but it is noticable.

Funny, I've been struggling with exactly this issue. Over the past few years my eyes have worsened to the point where doctors cannot find a contact scrip that works in both eyes: we have to compromise with one eye fixing far-away and the other fixing near. I had TWO optemtrists generate an Rx and they differed in all domains, with the astigmatic axis off by 90-degrees in both eyes! I've wanted to buy a lens kit and do it myself for years, but after reading how complex a process it is to find a compromise due to all the daily fluctuations, I'm ready to accept that my eyesight is just a mess and nothing can fix it for ALL scenarios.

You can't wear contacts for flying or passing the exam?

The best eye "hack" I've done is getting Lasik. I wore glasses and then contacts for about 20 years and got Lasik done 3 years ago. It's worth whatever it costs you.

There are some eyes that are somewhat risky to treat with lasik, such as having pupils that dilate to 8mm+

It's not worthwhile for nearsighted people beyond middle age. It also structurally weakens the eye so not a good thing depending on your occupation and hobbies.

I've read reports of worse vision in dark after Lasik. And what if my short sighness worsens over time (as it did so far). I don't think Lasik is the ultimate solution which works perfectly forever.

And now consider that your _other_ doctors are also mostly just guessing, often poorly, at the expense of your health. This is why medical error is the third leading cause of death in the US: https://www.cnbc.com/2018/02/22/medical-errors-third-leading.... The stats are likely to be even worse in less developed countries or ones where doctor is not as prestigious a profession.

> and she’s not happy to share the measurements with me as she fears I’ll run off and get my glasses made online

I hate this! Are they really allowed to do this?

"What's my prescription?" "Not telling"

They are most certainly not allowed to withhold it: https://www.ftc.gov/tips-advice/business-center/guidance/com...

TFA is most likely set in Germany, where different rules apply

Historically, at least in the Netherlands (and it seems also Germany), you get the eye test free as "service" because before or afterwards you'll then look for a frame that you like. Of course, under GDPR (or previously the DPD from 1995) you are totally entitled to learn what data they have about you, but going to get a free eye test and then ordering cheap stuff online is just a jerk thing to do.

I read in this thread that elsewhere on the planet, they're not free, and then of course you get the values. Would be super weird to pay for a test and then not get the result. (Nobody likes vendor lock-in.)

I've done eye tests before and not gotten glasses because it turned out not to be necessary, but it always felt really shitty. I always asked how much it was, as an offer to pay, but was never asked to pay anything. I'd be in favor of paying for what you use to avoid both guilt trapping and hard feelings.

I went for a Lasik consult recently and they said they have to dilate my eyes to get the most accurate reading since the muscles can compensate and give variable readings. It's true, my last two prescriptions differed from the reading they got with my eyes dilated. Maybe it was just an extra money grab but if it's true and I had known that before I would have asked them to dilate my eyes when I wanted to get glasses too.

This is amazing, however, I have the opposite problem: how do I measure for contact lenses?

I've never been able to get a good fit for my contacts although my glasses have always worked well enough. The weird thing is that when I go to get contact lenses, the retailer orders them according to my glasses prescription, but subtracts seemingly arbitrary values from it to arrive at the contact lenses' values.

I live in Pakistan, btw.

Yes, that's a real problem - and I think those "arbitrary values" even vary by manufacturer. The best strategy I can come up with right now is ordering a pair of contact lenses based on a "best guess", possibly by an optician, based on your values for glasses.

Then, check whether they are over- or under-correcting and order another pair with slightly different values under the assumption that your initial "best guess" was off. Then, compare and repeat..

Do you have a stigmatism? Contacts offten don't work well with people of stigmatism.

I do have astigmatism, actually. However, looking at the prescription of the author in the article, it appears that he does too!

Yes, I do. I had lenses with cylinders (for correcting it) in the past and didn't like them. They're larger and asymmetric - the lower side must be heavier so that they always align correctly on your eye.

With not-so-bad astigmatism, you can get away with not correcting it in your contact lenses. That's what I currently do. It works okay and brings you to a good level of vision (1.0 here in Germany, probably 20/20 in the US).

Ahhh, that won't work for me. I started off like that, but getting cylinders made a huge difference in my contacts. I've tried the bottom-heavy ones, as well as the ones with a "1" that's supposed to be positioned at the bottom manually. Neither has worked too well.

The shifting position isn't a problem, I think the bottom-heavy ones adjust fine with a little bit of practice, but the experience is never that good.

I have astigmatism as well and the ones I use are acuvue daily moist. They apparently use some blinking technology to keep them stable. To be honest, I didn't know they were supposed to remain stable until I saw your comments, so I guess they work well for me. There are only very specific situations where I get discomfort and they misalign for me, but a few blinks puts them back in their spot.

An ear-handle broke off of a pair of eyeglasses I had a few years ago, and nobody could repair it. I tried 4 shops, including a jewelry shop. Being that progressive-focus prescription lenses are expensive, I didn't want to buy a new set. (Progressive focus is similar to "bifocals".)

Hopefully shops with 3D printers etc. will give consumers more repair options.

> I have a few seconds to decide whether I see some letters better and this decision will decide which lenses I’ll have in my glasses for the next few years? Absurd!

From personal experience: don't do these tests if you're tired, have headaches or are otherwise impaired. For example if your eyes simply want to shut and you're forcing them to open the musculature will affect your vision.

I'm going for my regular eye test tomorrow, I'm similar to the author with toric contact lenses (for astigmatism) and glasses for all other times.

I'm not looking forward to the "does this look better or worse?" dance and can totally relate to the author's frustration!

Good luck!

I'm generally wary of anyone who says they're a perfectionist, because I usually find them to be absurdly picky about silly things for no real reason, but this guy has a point about not being able to tell if glasses are right for you based on staring at some letters.

That was a great read, but one of the summary conclusions jarred with me a bit:

> Want to optimize your medication? Read up on all relevant studies and guidelines.

I am surprised to have seen this penned by a doctor. Relevant studies and guidelines are a minefield for amateurs.

Very impressed my good man. Would it be possible to automate this process a bit and get some statistically sound measurements from doing it 100 times? Can we turn this into an online business? :D

Great read. Thanks.

I've also received lenses that don't match the prescription. My ophthalmologist says that source of error is common. So now I have the doctor's office verify my lenses.

> She seems to forget the fact that I’m a doctor

> As a doctor I know some things about the human eye

Something about these sentences identify our author here as German. And low and behold, it turns out he is.

A similar incident happened with me too. Visited an optician, immediately followed by a doctor the same day. The measurements varied by 1 whole digit!

So, anyone read the manual for the measurment instruments used and investigated what is the specified error of measurement?

Maybe variation can be attributed to that.

Eye fatigue gives a much higher difference than the error margin of the instruments.

Good story but I'm a touch disappointed as I came in expecting a story about making the lenses.

Suddenly I feel very less confident in my prescription that I just received

Wish he included a link for the kit of test lenses he purchased

It's a pretty generic kit sold on ebay from various chinese resellers. It's not too hard to find if you search for "optician kit" or so, price is around 180€ in Germany :)

I hope someone reads this and starts Stitch Fix for eyeglasses.

I would pay attention to what eye doctors call overcorrecting.. of course you see better but your eyes become lazier and lazier

expected to read an article about someone 3d-printing their own glasses, was disappointed


I wanted to be an Optometrist but went into software engineering instead. I think Optometry is fertile ground for disruption by technology. Similar to pharmacists, the only thing keeping so many employed is a cartel.

>I have a few seconds to decide whether I see some letters better and this decision will decide which lenses I’ll have in my glasses for the next few years? Absurd!

On the contrary, it seems totally logical. If the difference is so small that you can't assuredly decide between two options, either will do.

>How can a trustworthy decision be made in this not-real-life scenario of staring at letters on a wall? I want to be able to decide while going about my daily routine: Staring at computer screens, looking out of the window, looking into space. My daily routine doesn’t include staring at the same five letters projected onto a white wall and reading them out loud.

Yeah, so? Who told you you'll find anything more doing that, that you would looking at the projected letters?

>I went through with it and the pair of glasses arrived around two weeks later. Putting them on for the first time, my vision was just as perfect as with the trial lenses. Awesome! This was hands-down the best pair of glasses I ever had. Better yet, it was the first pair of glasses with which I could see better than with contact lenses (as those don’t have a cylinder).

For all the skepticism at others (eye professionals at that), did he checked his enthusiasm for placebo effect? Or the IKEA effect for that matter?

The guy seems eccentric in a creative way, but unbearable...

> For all the skepticism at others (eye professionals at that), did he checked his enthusiasm for placebo effect?

Yes. I have two pairs of glasses here: The optician-made ones and my self-prescribed ones. I have controlled for the frame - both have the same one.

I see much better with my self-prescribed ones. If you don't believe me, feel free to drop by and we'll do a blinded (heh) test. :)

> On the contrary, it seems totally logical. If the difference is so small that you can't assuredly decide between two options, either will do.

A slightly different way to interpret this would be to say that that particular axis of variation is at its limit, given the state of the other axes.

There are several axes, and they aren't perfectly orthogonal. Zeroing in on one can alter the best correction achievable on the other. Not all opticians will go back and iterate other axes, but I think it's a good idea. Lock X, find Y, recheck X given Y, etc.

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