Measurement with Refraction(?) Machine Process Issue or Am I way off mark?

Can anyone help demystify what they do when they measure your eyes with an Auto/refraction machine? That’s the machine they use to get your prescription right?

I went to my opthamologist last week for my eye check. (It’s been two years!) and the Assistant measured my eyes and said there is no change, only .25 in my left eye?! What? According to my Snellen and Distance from Eye measurement, I have gone down about .75 in each eye! I’m suspecting that the machine isn’t measuring from 0, but puts in your existing and just gauges for slight change.

I tried to talk to my opthalmologist about it, but he even sees .25 as so slight as to be changeable from day to day, and he refused to write me a new script.

It may be time to switch eye doctors because he’s now way too rigid to support my vision progress. I was going to him because I think he’s a good guy for ‘eye health’ but optics-wise, can’t go by their measurement, nor is he giving me any way to accurately ‘check-in’ year by year. Maybe I just need to go to an independent source and remeasure not letting them know my current diagnosis? Or does anyone know an optometrist or opthalmologist that they can recommend in the New York City area?

I was hoping that there would be measurable good news to share with the group :neutral_face: . First I was upset, then disappointed :disappointed:. I’m back to making sure I’ve got the basics, but I wanted to check this out with our group.


This is why I will not go to have my eyes measured again. I consider the cm measurements and Snellen accurate enough. Even if the improvement I see is ‘subjective’ this is good enough for me, as I am the subject who sees through my eyes. I need no confirmation of this by any opto or ophthalmo.
Yesterday, in glorious sunlight, I was sitting outside looking at the trees and shrubs, near and far, and several times had to remind myself that I was not wearing glasses (not that I ever do) and no narrow-minded opto or ophthalmo would be able to persuade me that my vision had not improved. Cast off the dissapointment and sadness, you don’t need these on the EM journey.
Others with more knowledge will reply on the issue of the accuracy of autorefractors, but I have already read here and there that they often lead to overprescription…


Yes this is how I feel too. And just think about how little the CM readings can vary based on .25 dioptors and the lower dioptor range. Although I cannot answer the specific question about the auto refractor. I know that my vision has improved and if I went to the opto that I have seen before I will just get discouraged if they do not show an improvement.
Before I officially started the EM improvements I was trying some bates method with a slight reduction in my glasses. The last visit I had with the optometrist was very upsetting to me because he scoffed at me when I said I was trying to improve my eyesight. But I am going to look up the auto refractory question. I am curious. I believe the numbers I had at that time showed a lower dioptor than the actual prescription I was given.

I have been doing the same, and found something:
where the conclusion reads 'Conclusions: Our results suggest that, in a clinical environment, subjective refraction produces a more accurate and acceptable spectacle prescription than an autorefractor.
(Clin Exp Optom 1998; 3: 112–118)’
What alarms me even more is this: ‘Having reported initial discomfort, many subjects indicated that they had adapted to the spectacle lenses over a two-week period.’
This was worse for the autorefractor prescribed lenses. How quickly one can grow into overcorrection!
@claire_szeto this is not the only time such a study has been done, and the autorefractor has come out ‘worse’. I seem to remember @varakari also mentioning this.


This study compared 3 different types of autorefractor machines and the different dioptor ratios. Although I am not familiar with all the terms they used it does appear there can be changes of .6 dioptors, not sure how that translates with the .25 increments used, so yes it seems that the machine used can make a difference. Also it in the reading it seems to indicate that the same machine could show a difference in readings on the same person.
Also I read a article that said the fogging of an autorefractor can change the reading and therefore cause overprescribing especially in children. Although it does appear it is more common now to use an anti fogging autorefractor.

1 Like

I should have asked you this ealier, but was the autorefractor the only eye measurement they took?

I trust HOYA refractor (Japan) which is in the optics near me.

I have contact lens Rx -8/-8.5 R/L respectively, and that refractor showed -8.25 for both eyes.
So I have had myopic blur with right eye and hyperopic (accommodation can lift it up) blur with left eye. Now hyperopic blur with both eyes, because I enjoy some improvements from reduced lens, “passive” active focus and Atropine drops, so I just use +0.75 glasses over contacts for distance.

Also it showed -2.25/-1.75 R/L astigmatism, whereas doctor’s refractor (it’s likely Zeiss autokeratorefractometer) showed I have only -2/-1.25. But reality is quite different however, I have too weak astigmatism correction with cylinder -1.75/-1.25 toric contact lenses, I see ghost images here and there (both eyes).

My centimeter measurements are also very close to HOYA refractor.

So again, it varies from machine to machine, brand, calibration (don’t forget, calibration is a key for such things).

Don’t ever remind me about test lens kits, I always had a bad time with them. Super unreliable in severe myopia cases.

So I vote for (good, calibrated, new) autorefractor and centimeter measurements (do latter with enough care, make sure you measure from correct point, to correct point, with correct angle from eye to test card, also you may try to shift every 0.25 diopters, use for instance Javascript function to quickly print you all diopter centimeters from -0.25 to -20.00, do not use text, but use circle with rotable lines, 90deg opposite each from other).

@Ursa Yes! I’ve been going to him for about 10 years. The autorefractor is somewhat new, and when he first got it in the office, the assistant would use it before I saw him, and he would verify the results the old fashioned way with those lenses (better or worse?). Now, it appears, whatever the assistant measures, is all it is. I think that if he has the conceptual idea that eyesight doesn’t change, he’s not at all curious to see if there is change, especially as I’ve basically had the same prescription the whole time I had seen him prior to Endmyopia habits.

@miffiffi I had to read this several times to get this new information in! I have not heard of this method of centimeter measurement. Can you post a picture and/or where to get this circle with diopter centimeters? I want to try it.

As a graphic designer, I’ve long made peace with the fact that although 12 point font is a good general guideline to do close AF work, there’s not alot in this size. What’s important is consistency…the same book or same published newspaper, etc.

It’s not commonly known how cost cutting has impacted paper printing. To fit more information in, few books and print materials have 12 point font. I have a graphic designer’s transparent font guide, and I looked at over 10 books last week with it, not one had font size larger than 11 point! Last year I designed a book, and started in 12 point font and in the initial design review, my client told me it looked too large, like a child’s book. She showed me her other book published by Princeton Book Review, and the font was literally like 8 or 9 point!

1 Like

This is very ignorant, and lazy, of him. Imagine installing a new piece of equipment and not learning about its potential for overcorrection. And then imagine not wanting to take the time to make sure with a phoropter. Of course, if he has been seeing you for 10 years, has your records for this, there has been no change in that time, and he does not believe eyes can improve, that would just confirm what the autorefractor told him. Perhaps go to someone else next time, who does not have your records, and insist on a phoropter test as well.

1 Like

Instrument Myopia

The ciliary muscle is controlled by your conscious perception; you can even learn to control it directly. When you look into a machine that is close and measures your eyes’ optics, it can easily happen that the eyes accommodate to near by a significant amount, simply because you know you are looking at a near object.

See also the Wikipedia article on instrument myopia.

My autorefraction readings suggest systematically more minus lens use than the optometrist owning the machine prescribes, as well as my own focus reach measurements show.

With current technology, it is not advisable to rely on autorefractors alone when choosing your glasses.


As an addicted book reader, I am more and more irritated by the quality of the paper, the skimpiness of the margins and the letter size of paperbacks. I write graded readers for non-native speakers of English (Tibetan children in India), using the free Scribus software and convert them to pdf. The printers in India have to convert this to another form for offset printing, and although they cannot mess with the contents of the pdf, they have to be told each time to make the page identical to my homeprinted version of the booklet.
Font size, interline spacing and adequate margins are essential for children who have enough trouble already engaging with what they are reading. We don’t want to strain their eyes as well. :wink:


Bates talks about this as the main reason for myopia
“The eyes are focused on being close instead of distant.”
He argues that this can happen for a multitude of mostly mental reasons.
Once the brain is used to doing it then it has to be taught to stop doing it.

Well, it’s not the reason for my myopia, but I’m starting to wonder if maybe it was for Bates or Mark Warren. There’s no requirement that all myopia is caused by the same mechanism; it could be that all three of axial elongation, ciliary muscle spasm, and bad motor control of the ciliary are often contributing to myopia.

If that’s what’s happening, then the correct way to address it would differ depending on each person’s distribution between the causes. It could also explain why active focus is so important for some and barely works at all for others.


Great point, @Varakari . We should go with what we know, but also be open minded that what we know isn’t everything. It’s not often that a single habit-based variable is responsible for a biological malfunction like myopia.

Not all up-close is the same. Not all people’s biology is the same. Results will vary. Bad habits will vary outcomes too.