Is auto refracting machine at optometrist shop is correct?

Yesterday i visited my optometrist because i was not doing active focus that often so i thought that my diopters might have increased so why not get them measured and start again. Now when i was seated on seat and he calculated my diopters with auto refracting machine( i guess i am taking the right name of machine, it is the one which have hot air baloon or barn and road). The machine was givin less diopters but i was unable to get 6/6 with them and my old prescription was givin me 6/6. The difference between the new diopters and old ones was also about 0.50 D.

My new prescription was
R 2.25s 0.75c
L 2.25s 1.75c

My old prescription was
R 2.75s 0.75c
L 2.50S 1.25C

All diopters are in negative.

I am also not wearing my glasses since 6 months and for god sake my optometrist understand what active focus is and also he helps me with it. He said that your eyes are adapted to blur. So he suggested me to go with the prescription that machine is giving and he said that my eyes will adjust with low diopters if i wear them quite often and also i can contine AF thing.
Anyone here know about this then i am waiting for your views regarding this🇮🇳

The consensus here is that we do not trust the machine and that we take the opto measurements with a grain of salt. Though it does sound like you found a very good opto! He is quite right that you about the blur adaptation and that you need to wear proper correction to leave you with at resolvable amount of blur.
With you cylinder diffs and normz are recommended. More on why on my channel :grin: Reannon - YouTube and in these articles: Differentials - EndMyopia Wiki, Normalized - EndMyopia Wiki
Best wishes


It is not very likely for the autorefractor to read less unless there is some real improvement in your eyesight. It is more common that the opto takes the autorefractor result and reduces from that - that’s what my opto did every time. I.e. it is more common for the autorefractor to be the cap on correction.
Reasoning from a high street opto: the autorefractor doesn’t take the additional acuity into consideration - additional acuity provided by binocular vision and by peripheral vision.

It is possible that your previous correction was not correcting you to 6/6 but to something slightly better, so you are experiencing a perceived loss of acuity with the lower prescription as that “only” gives you 6/6. Also you got a reduction on your cyl which takes weeks to get used to - adjusted in your brain.

really? My auto-refractor measurements have always given a weaker prescription than what the opto gave in the end i.e. they always added more negative power on top of what the machine had said

so I always got the impression the machine UNDERestimates needed lens power and the opto OVERestimates it (or tries to provide sharp night vision +0.25 D)

Obviously not all optos are the same but still you surprised me with this.

I’ve always received less correction than the autorefractor result and as I said many times I always asked for correction better than 20/20.
I asked the why from optos this year and they said they only saved the prescription data not the autorefractor as the latter was not relevant info (?!?!) just an indication on eyesight disregarding some important elements (the person’s ability to see better even if individual eye’s acuity measured by the autorefractor would suggest that was impossible)

Do you want to put a vote up to see what others’ experiences are about over or under correction compared to autorefractor result?
Maybe I’m the only one who gets undercorrected for 20/15 when compared to the autorefractor measurement?

could do.
the other thing I noticed is they like to move sph and cyl diopters around, like if they add 0.5 D cyl they reduce 0.25 sph compared to the autorefractor result, but as we know, sph equivalent

but my data is limited as I’ve only really checked compared to the autorefractor since I’m aware of EM, before, I don’t know what autorefractor values I had