# Talking about glasses



## Du_sud

Hello, everybody!

I would like to know how an English-native speaker would talk , informally, about the diopters of the lenses in his/her eyeglasses.

Do these sentences sound correct to you guys?

"She wears glasses with three diopters of myopia in both of the eyes."

"She wears glasses with three degrees (or "three degrees of myopic severity") of myopia in both of the eyes." 

Thanks to you all.

Du_sud


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## GreenWhiteBlue

Most English speakers would not say these things, or understand them.  This is the technical language of opticians only.


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## Du_sud

Well, so can anyone tell me how an English-native speaker would say that "informally" when talking about his/her glasses??


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## Lis48

Informally I would always say " Her glasses have a strength of +3 " but at an optician I would ask for glasses with "a diopter strength of +3."


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## panjandrum

I don't know anyone who would refer to the strength of their glasses in these terms. I have worn glasses for many years and I have no idea what numbers appear on my prescription.


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## Loob

I agree with GWB on this.

I have never said the word diopter to an optician or anyone else.  The prescription the optician gives me looks very much like the one in this Wiki article.  Supermarkets and chemists sell "over the counter" reading glasses in varying strengths; but to the best of my recollection, the strengths are just given as numbers, with no reference to diopters.

Informally, we tend to say "she wears strong/thick glasses" rather than talking in numerical terms.


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## nzfauna

I have heard my optometrist use "diopter" as you have in your first example.


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## elroy

panjandrum said:


> I don't know anyone who would refer to the strength of their glasses in these terms. I have worn glasses for many years and I have no idea what numbers appear on my prescription.


 I, too, have worn glasses for many years but I do regularly refer to the strength of my prescription using numbers, and I'm not the only one. Just the other day I was talking about it with two other glasses-wearers and a "rebel" who should wear glasses but doesn't , and we all used numbers. Granted, we were talking in German, but I have had similar conversations in English before. I just mentioned that example because it was the most recent.

Anyway, to answer the original question...

An informal conversation about these things might go something like this:

-So what's your prescription?
-Well, it's negative 2 in one eye, and negative 3 in the other.
-Oh, that's nothing! Mine is negative 5.25 in one eye and negative 6 in the other.
-Oh, wow, that's really bad. I bet you can't do anything without your glasses on.
-That's right - I'm helpless without them!

Often the word "negative" is dropped among near-sighted folk because it's understand that it's negative.

But I've never said "diopters" or "myopic severity."  I don't even know what any of that means.


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## Rana_pipiens

In a conversation with someone who isn't a doctor, optometrist, or other specialist, it would be much more usual to say *nearsighted* rather than *myopic* (adjective) or *nearsightedness* instead of *myopia* (noun).  The word *shortsightedness* also gets used, although its metaphorical meaning of "failure to plan for the longterm" is becoming more common than the literal visual meaning.

I doubt that a correction of -3.0 diopters would be described as thick glasses, especially since the advent of high refractive index plastic.

*Presbyopia* is usually called *farsightedness*.

I would guess more people know their visual acuity score, 20/something, than their correction. (Apparently three diopters is in the neighborhood of 20/300.) Certainly I'd never come across the term *diopters* until being told I didn't qualify for an advertised eyeglass price  because the cutoff was 10 diopters -- I'd been wearing glasses for probably thirty years at the time.


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## MagdaDH

In the UK, I have heard (and used) "minus 2", or "plus 3" etc, or just short/farsighted.


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## Du_sud

Hello again!

I really liked the example of the informal conversation talk given by elroy above. That's exactly what I meant when I posted the thread.
Now, what I would like to know is if that "example talk" sounds okay to most of you, native speakers.

Thanks for all your hints!


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## AngelEyes

Elroy's examples are very normal in AE, but I have to add this comment. If I told most people I was -3.75 in my right eye and -3.25 in my left, they'd look at me and go "HUH?" 

Most people don't care what their prescription is. Contact lenses wearers are the most knowlegeable.

People might know if they have 20/20 vision or a variation of this according to their individual eyes, though.

I'm not saying many people couldn't give you their prescription numbers, but I'd say the number of people who don't know far out-weigh the number of people who do. 

Older adults are far more likely to be able to tell you their reading glasses prescriptions. For instance, "I wear a +1.50." 

I wouldn't be surprised if almost all of them can tell you what they need to read and that's the way they'd say it.

*AngelEyes*


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## Forero

We say "a correction of minus 3" for eyeglasses of a certain strength used to correct for myopia.  "Diopters" is understood.  The "minus 3 (diopters)" actually refers to the strength of the lenses, not the myopia or what-have-you of the eyes.  We use diopters for ordering telescope, microscope, and camera lenses as well.  Plus is for magnifying glasses, minus for minifying glasses.  I think +2, for example, means that parallel rays entering the lens are brought to a point (focus) 1/2 meter on the other side of the lens, and -3 means that rays emanating from a point 1/3 from the lens come out parallel on the other side.


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## GreenWhiteBlue

I have been wearing glasses for more than forty years.  Like Panjandrum, I have no idea what my exact prescription is; that is something the optician needs to worry about, not me, as I am not going to be making my own eyeglasses.  I would find the conversation described by elroy to be unusual to the point of being strange.


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## AngelEyes

GreenWhiteBlue said:


> I would find the conversation described by elroy to be unusual to the point of being strange.


 

Not me, GreenWhiteBlue. There are plenty of us out here who would enjoy elroy's conversation and be able and willing to converse with him on this subject.

Everyone is different. 

*AngelEyes*


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## Du_sud

Mmmm... well, I myself have been wearing shoes since I sarted to walk and that was also over 40 years ago. Although I don't make my own shoes, I have always known what my size for shoes is.

Well, I guess it's just a cultural issue. Where I come from, it's extremely "normal" to know what _diopter_ your lenses have, despite the fact that we ourselves do not use that word (in our language). 

Thanks again!


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## cuchuflete

GreenWhiteBlue said:


> I have been wearing glasses for more than forty years.  Like Panjandrum, I have no idea what my exact prescription is; that is something the optician needs to worry about, not me, as I am not going to be making my own eyeglasses.  *I would find the conversation described by elroy to be unusual to the point of being strange.*


Exactly!


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## Du_sud

...couldn't agree more with AngelEyes!


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## GreenWhiteBlue

Du_sud said:


> Mmmm... well, I myself have been wearing shoes since I sarted to walk and that was also over 40 years ago. Although I don't make my own shoes, I have always known what my size for shoes is.


 
Well, then, I suppose you can just disregard the advice you are getting from me and from Panjandrum and cuchuflete, and think that this conversation about eyeglass prescriptions is perfectly common.

Of course, I would say that would be dead wrong, but apparently I must be too ignorant to be taken seriously, since I don't know what my eyeglass prescription is, and think that people who find such things to be common topics of conversation are a little odd. I hope Harvard doesn't want my Master's back, although CUNY will probably recall the Ph.D. once they learn that I had never seen or heard the word "diopter" in my life until today.


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## AngelEyes

GreenWhiteBlue,

Then I guess if I were to start talking about my Base Curve and how it's different in both eyes, it just might send you over the edge? 

No...what I really mean to say is that everyone is different. What interests one person, another finds strange or boring.

With respect to this thread, the suggestions for conversation are valid and not unique, at least to some people.

Again, people who wear contacts like I do might be more inclined to know their prescription numbers.

I'm sure there's a vast group out there who feel like you do, though.

*AngelEyes*


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## cuchuflete

I have seen the word diopter, about once every four years when I get an eye exam.
Those who care more might call it a vision exam.  Were it not for those infrequent
visits to the optician, (or is it optometrist, or opthamologist?), I might have thought
that diopter was a cross between a helicopter and a catamaran.

Seriously, AngelEyes is correct in saying that there are people who care more about such things, and hence know what the words mean, and even use them.  Until this thread, I had never come across one of those people.

Maybe they have been right in front of me all these years, and I'm just nearsighted.


You asked what normal people say in conversation.  OK.  If and when you find what pass for "normal" people
in this region, and they stop discussing the weather, politics, summer traffic on the Wiscasset bridge, and how the
lobster catch is doing, you might hear this:

_A.  I like your glasses.  Are you nearsighted or farsighted?
B. Can't say for sure.  I use these glasses for driving, and I've got reading glasses at home.
_


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## Rosa7

Just to add another person to the list who would have a conversation about eyeglass prescription strengths with other people who wear glasses.

Not to the decimal point, though - we're not that keen! 

It comes in useful when you want to go snorkelling and hire some equipment to see the colourful fish properly:

Staff member: "What strength are you?"
Me: "About 3, I think"
Staff member: "Try these on"
Me: "Yeah, these are good"

Of course you could just keep trying different ones on till you found some that worked.


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## Du_sud

That also seems to answer my original question perfectly, Rosa7!


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## cuchuflete

Du_sud said:


> That also seems to answer my original question perfectly, Rosa7!



No, that seems to correspond perfectly to your preconception of what the answer ought to be.  You have had three distinct classes of answers from native speakers:

1) Those like Rosa7 who use modestly technical terms in general, informal conversation;
2) Those who use more technical terms, in conversation with others who share a greater than average awareness and interest;
3) Those who use no technical terms at all.

I think it's fair to say that the real answer to your question, however imperfect it may seem, is that all three groups exist, and that there is not a single "perfect" answer.


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## Rosa7

cuchuflete said:


> No, that seems to correspond perfectly to your preconception of what the answer ought to be.  You have had three distinct classes of answers from native speakers:
> 
> 1) Those like Rosa7 who use modestly technical terms in general, informal conversation;
> 2) Those who use more technical terms, in conversation with others who share a greater than average awareness and interest;
> 3) Those who use no technical terms at all.
> 
> I think it's fair to say that the real answer to your question, however imperfect it may seem, is that all three groups exist, and that there is not a single "perfect" answer.



But some good general advice would be to avoid talking about diopters etc (never heard of them!) unless you know that the person you are talking to is familiar with such terms.


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## Du_sud

Cuchuflete, if you read my first question you will see I asked how a native speaker would say that "informally". I do appreciate (almost) all the replies I got, despite the fact that some people went more into the technical world. I just needed a common, regular - well, again, common to a certain group of people - way to talk about the prescription of your lenses. I could never imagine my simple question would be so interesting as to have 2 pages of answers! I'm thrilled!


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## Forero

I do use some caution when talking about diopters with people where I work, although several of them (one could never guess which, without asking) know what diopters are.

Now those who designed the original optics for the Hubble Space Telescope could have saved a lot of trouble, time, and money if they had paid more attention to their diopters.


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## Dimcl

About the only answers I hear with regard to what "type" of glasses someone is wearing are "bifocals", "trifocals" and "progressives".  I've worn glasses since I was 9 years old - back then, I was far-sighted; now, I'm near-sighted.  Ah yes, I also have astigmatism.  I have never once heard diopters discussed in a casual conversation about the riveting subject of wearing glasses.


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## Forero

For some reason, we don't talk so much about astigmatism beyond saying we have a little or we've got it "really bad".


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## panjandrum

Du_sud said:


> Cuchuflete, if you read my first question you will see I asked how a native speaker would say that "informally". I do appreciate (almost) all the replies I got, despite the fact that some people went more into the technical world. I just needed a common, regular - well, again, common to a certain group of people - way to talk about the prescription of your lenses. I could never imagine my simple question would be so interesting as to have 2 pages of answers! I'm thrilled!


The thing is, from my perspective people don't talk at all about the prescription of their lenses. I have had conversations about near-sighted, far-sighted, astigmatism, tints, coatings, bifocals, varifocals, contact lens types and frame types.  The prescription of the lenses has never entered into the conversation.

I wonder is there something about the way we get new glasses/lenses?
It is normal, here, to go along for a sight test and if the prescription has changed to get the new glasses/lenses from the same place.  So although I always get a copy of the prescription I never look at it and I do nothing with it apart from put it away in a drawer.  I need to know my shoe size to buy shoes.  I don't need to know anything about my prescription to buy glasses.


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## elroy

Maybe it's a generational thing.

I imagine that twenty years ago, contact lenses weren't as common and popular as they are today, and that you could pretty much only get them at an optometrist's. Today, it is very common to simply order them online, and in order to do that, you *need* to know what your prescription is.

It's a little different with glasses, as you do not usually order those online (or do you?), but I find that many glasses-wearers my age do in fact know what their prescription is. Maybe it's because in many places it's possible to get new glasses without an eye test, so it could be enough to know your prescription. Maybe it's because it's simply a convenient way to compare the severity of your near-sightedness with that of others. Maybe it reflects an increased level of consciousness of and concern about physical impairments.

I can't say for sure what the reasons are, but I can say that my conversation would not be "unusual" or "strange" to everyone, and none of it has to do with how educated anyone is. As AngelEyes said, different people are more interested in and/or knowledgeable about different things. I wouldn't consider a fellow glasses-wearer ignorant or unrefined if he didn't know what his prescription was, but at the same time I don't consider those who do odd or peculiar.

I like Cuchuflete's summary in post #24. There are people in every one of those groups, and they are all equally normal. Isn't it the same with almost everything? If we were all enthusiastic about and indifferent to the same exact things, life would be unbearably boring.


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## Lexiphile

Am I the only one who has noticed that all the posts that deny the use of the word diopter are from America, and all those from outside America have at least heard about the numbers? [neither group excludes the other!!]
In America, one speaks of 20/20 vision. I don't remember what that means, and I've certainly never heard it in Europe.
Despite having my feet now set firmly in European concrete, I'm inclined to agree that the term diopter, the unit of correction in the lens, is not common currency. However, the numbers (with sign) certainly are widely understood here. My optician actually tells me what (numerical) correction I need.

So how the original poster's converstaion should be phrased is, like so many things, a matter of location.


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## panjandrum

Dioptre hasn't featured in my conversation since I studied optics - a very long time ago.  I thought I would mention that because BE spells it dioptre, not diopter


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## Du_sud

Hello again!

As I said, this thread has turned out to be more interesting than I could have imagined.
Let me try to make my question in this thread a little bit clearer. 
As I said, here in Brazil, everyone wearing eyeglasses or contact lenses will know what the diopter for their lenses is, as we also know about our shoe size ( ok, panjadrum -  ).  I guess it's probably just a cultural issue. As it is so, I wondered how you native speakers would talk about that. Well, it seems most of you simply don't - again because it may be a cultural thing! And THAT'S OKAY! 
Also, I have to mention the fact that when I ask you guys how you would talk about that "informally", I, by no means, suggest anything like:

Peter: "Hi, how are you?"
Mary: "Fine, and you?"
Peter: "Fine, too. What is your diopter?"
Mary: "-3.0."
Peter: "Ok. Bye!"
Mary: "Bye!"

The conversation about diopter, strength, lens thickness, etc, etc, would, OF COURSE, be part of a logical context!!!

Let's see what will come from that now...  (smiles)

Thanks again!


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## Sepia

Lis48 said:


> Informally I would always say " Her glasses have a strength of +3 " but at an optician I would ask for glasses with "a diopter strength of +3."


 
Except it would be -3 in this case. She is short-sighted, right?


Oh, somebody just mentioned that, I see ...


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## Lexiphile

Peter, a salesman in an optical goods shop: "Hi, how you doin?"
Mary, a potential customer: "Fine, thanks. Ya'll got any readin' glasses?"
Peter: "Sure do. What is your diopter?"
Mary: "Ahh I dunno. 'Bout 3.0, maybe. Cain't read the health warnin' on my ciggies pack"
Peter: "Here, try these."
Mary: "Hey, they's great. How many them diopeter-thingies is they?"
Peter: "+3.0."
Mary: "Wow!"

But more seriously, I don't think that even in Europe, where we know about such things, would anyone actually talk about them, except to an opthamologist or optometrist. And then he might use the word, but we wouldn't. I think you'll need to elaborate on exactly the kind of conversational situation you have in mind.


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## Du_sud

Well Lexi, you probably don't wear glasses/contacts. I have German friends and,  while visiting them in Germany, in a talk about this issue, OF COURSE in a context and not out of the blue (smiles), they knew the "numbers" - to put it simpler - of their lenses. So do my many other Dutch friends...


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## Lexiphile

As it happen, Du, I've worn glasses for the last fifty years.
And I didn't realise you wanted your informal conversation to take place in Germany -- that explains it!  EVERYBODY in Germany is always talking in great technical detail about his health problems. 
Here (in Germany) we certainly do talk about _Dioptren_. So the conversation in your original post would be OK here.  But I still can't imagine such a conversation in Britain.  And in Texas....?  Doubtful.  At the most, people might compare the thickness of the lenses, or make fun of the kid with the really thick ones.  As I mentioned earlier, in America we might compare (or might have compared, in my case) vision-test results: "I got 20/20, what was yours?"  But that's not the same thing, is it.


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## Outsider

Du_sud said:


> Mmmm... well, I myself have been wearing shoes since I sarted to walk and that was also over 40 years ago. Although I don't make my own shoes, I have always known what my size for shoes is.
> 
> Well, I guess it's just a cultural issue. Where I come from, it's extremely "normal" to know what _diopter_ your lenses have, despite the fact that we ourselves do not use that word (in our language).


When you buy a pair of shoes, you need to tell the shop assistant what's your size. But when you buy new glasses you bring a prescrition from your doctor that contains your diopters. The information is all there; you don't need to know it. I don't know what are the diopters in my glasses by heart. On the other hand, I remember several people asking me how many diopters I had, when I started to wear glasses. I don't know the precise figures, but I know it's not much (less than 1 in absolute value, I think).

But I agree with you that this must be a cultural difference. One's medical conditions are a common topic of conversation in Portugal. I guess Brazil is a little similar in this respect. (And Germany, from what Lexiphile says!)


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## Du_sud

(laughing here)
No, Lexiohile! I didn't / don't want my conversation about glasses to take place in Germany! I mentioned those two European countries because you said, "But more seriously, I don't think that even in Europe, where we know about such things..."

As for what Ousider said, talking about health/medical conditions is NOT my favorite topic of conversation, nor is my friends'. Well, at least, it is not for a while. I'm sure it will be when I grow older... (smiles)

I guess I simply will NEVER ever talk about "numbers in lenses/contacts" to an English native speaker. From what most of you have written, I assume this topic is almost like a taboo, something like asking how much money one makes, or how much money there is in one's bank account! Or, asking what the distance between the Earth and the Moon is - only some astronomers will probaly know that, just like the opticians and alike will know about the "numbers" for your lenses. (I am not even using the word diopter/dioptre anymore , mind you! )  

Thanks again!


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## elroy

Du_sud said:


> I guess I simply will NEVER ever talk about "numbers in lenses/contacts" to an English native speaker.


 That would be a very unfortunate reaction to this discussion! Please go back and read my posts, AngelEyes's, and Rosa7's. 

I'm not saying _every _glasses-wearer will understand what you mean when you refer to numbers or ask about them, but so what? If someone gives you a blank look, just explain what you mean. Most people will appreciate learning something new. 





> From what most of you have written, I assume this topic is almost like a taboo, something like asking how much money one makes, or how much money there is in one's bank account! Or, asking what the distance between the Earth and the Moon is - only some astronomers will probaly know that, just like the opticians and alike will know about the "numbers" for your lenses.


 Ok, I think you're exaggerating just a tad.  The topic is not particularly sensitive, and the numbers are no more arcane than shoe sizes. It's just that, as others have mentioned, you don't usually need to know them (as opposed to shoe sizes), so fewer people do. But just knowing your numbers doesn't imply that you actually understand what they refer to, beyond knowing that higher absolute values mean thicker lenses! 





> (I am not even using the word diopter/dioptre anymore , mind you! )


 Now _that_ would be sensible.


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## Du_sud

Elroy! I was so grateful to you about that example conversation you wrote! Do read my comments after you had written it! And I also made comments on AngelEyes' and Rosa7's replies! 
As I said, I appreciate everybody's contributions - even the technical ones, despite the fact I just wanted to know a "simple, informal" way to talk about the "numbers" for the lenses in your eyeglasses/contacts.

Now, besides learning several ways to talk about that , I also found out another thing about cultural differences, and I guess that's what these forums are also for, right?

This conversation topic is quite common (in an appropriate context) among us here in Brazil, just like it is about our shoe size (also, appropriately placed). I have noticed, after all these replies, that's not what happens among English native speakers.

Now, when I said I would never talk about that to a netive speaker, I really didn't mean it. (smiles) I like having some nice debates, learning , and when possible, also teaching new things!

Thanks!


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## AngelEyes

Du_sud said:


> Can I just know how exactly you asked your son about his glasses? Can you tell me what exact words you used?


 
This is actually your original question, so it takes us right back on-topic.

I called him and asked:

"What are your prescription numbers for your contacts? Do you know them right offhand?"

He hesitated while he thought for a second, but then he gave me his right eye and his left eye numbers.

You wanted plain-speaking words for a casual way to ask your question, and this is one very simple example.

Amazing that this thread took on a life of its own.

*AngelEyes*


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## Du_sud

I have been asking how to say that in an informal, simple way from the beginning!

Now I would like to know if a native English-speaker, no matter what country he/she comes from, would be able to know what AngelEyes was talking about in the example she gave or if there would still be doubts about what she meant.

Thanks again!


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## Loob

I don't wear contact lenses; I wear glasses.

If AngelEyes asked me the same question with "glasses" replacing "contacts", I would understand she was asking about my prescription, but I would have no idea what to say to her. If she was really insistent, I might dig out my copy of my prescription, assuming I hadn't lost it.  I would then read out *all* the numbers on it and leave it to her to make what sense of it she could.


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## panjandrum

What you have been asking about from the beginning is "how an English-native speaker would talk , informally, about the diopters of the lenses in his/her eyeglasses," - which AngelEyes has not yet told us.  
What, I wonder, did her son say in reply to her question?


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## Du_sud

There seems to be a light at the end of the tunnel now. At least, one native speaker understood the question, "what are your prescription numbers for your contacts/glasses?" I don't think everyone would/should know the (exact) numbers, but, seemingly, comprehensible talk has been established there.  Or am I wrong???


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## AngelEyes

Du_sud said:


> Well, so can anyone tell me how an English-native speaker would say that "informally" when talking about his/her glasses??


 
This is the post that clarified for me what Du_sud wanted to know because _dioptors _is not a word I'm familiar with. When I realized it was just the strength by numbers of a person's prescription - be it for regular glasses or contact lenses - then it was very simple to answer that a lot of people in the U.S. know their numbers.

When I asked my son what his prescription numbers were, he replied, _"I'm -3.75 in my left eye and -3.25 in my right one." _This is not a guy who cares about all the tiny things in life, so he was a good test subject, in my mind. 

Also, very often your prescription strength will be weaker for your contacts than for your regular glasses. Some people may have two sets of prescription numbers.

Maybe where the confusion has come in is that it started off very technically focused with the word _dioptor_. Once it was made clear (to me)that what was really wanted was just plain-speaking in order to ask for this information, it became much simpler to answer the questions.

*AngelEyes*


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## Loob

Du_sud said:


> There seems to be a light at the end of the tunnel now. At least, one native speaker understood the question, "what are your prescription numbers for your contacts/glasses?" I don't think everyone would/should know the (exact) numbers, but, seemingly, comprehensible talk has been established there. Or am I wrong???


Comprehensible words, maybe.

Comprehensible talk - if by that you mean communication - no.

I hope you are not expressing exasperation by your reference to light at the end of the tunnel.  That would be most unfair to all the people who have tried to help you.


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## Du_sud

By no means would I be unfair! I have been thanking everybody over and over.
May I ask how an Englishperson would ask such a question then, as it seems the American way still does not sound that clear to a British?

Now it seems there are different ways to ask/say about this thread issue in the different English-speaking countries.

I'm curious to know what they all are!

Thank you so much for all your information!


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## AngelEyes

Loob said:


> I hope you are not expressing exasperation by your reference to light at the end of the tunnel. That would be most unfair to all the people who have tried to help you.


 
Du_sud is only trying to express his gratitude to us for sticking it out and explaining in all shapes, forms, attitudes, opinions and anything else each of us may have used to answer the question to the best of our ability.

_The end of the tunnel _means Du_sud is the one who is finally understanding what all of this means. It's not a reflection of feeling exasperation toward *us *because *he* is confused. He's frustrated with himself, I think.

I don't remember how many post counts Du_sud has, but I think he is somewhat new to the Forums. It takes a bit to acclimate to this environment. When you add the differences in languages, a little bit of compassion and kindness - and a lot of leeway for a while - never hurts. 

*AngelEyes*


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## Loob

You're right, AngelEyes, my remark was uncalled-for and I apologise to Du_sud.

Du_sud, I don't think there would be different ways to ask the question in American English and British English. AngelEyes' formulation is fine. 

It's just that many people would never ask the question; or if asked it would not know how to understand it or to respond. I am one of them.


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## panjandrum

There is no standard, or normal, or conventional way of asking such questions, or of giving the answers, here.  That has nothing to do with sensitivity of the topic or reluctance to discuss it.
It simply does not normally arise as a topic of conversation.
If it does, any of very many possible dialogues would be used.
The suggestions and comments above are, generally, relevant.

The nature of the conversation will vary enormously depending on the extent to which the participants are familiar with the terminology either because it happens to be a subject they discuss frequently, because they are professionally involved, or because they have sufficient knowledge of optics.


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## Wobby

I studied A Level Physics, and we had a topic on lenses, hence I know what 'dioptres' are - however, it is quite specialist knowledge, so many people probably wouldn't (unless they happen to be interested in that sort of thing, take heed of the numbers on their prescription, or buy lenses online). Even then, I would not know the strength of the lenses in my glasses.

It's kind of different to shoes - in terms of buying glasses, I would have an eye test, then the optician would give me a prescription. Then I would chose the particular frame I want, and they would sort out fixing the lenses to the frame while I go away, and then I would come back, pick them up, and fill out the rest of the prescription.

It is not like shoes in the sense that I would not expect to walk into an opticians and find lots of frames with lenses already fixed to them of various strengths, and I being required to say 'I need glasses of strength *x *in this eye, and strength *y* in the other, please could you show me the glasses that meet this requirement?', because then in terms of frames, you would be restricted in which ones you could choose, unless they only happened to stock one particular frame with varying strengths in many different permutations, or you had to choose the correct opticians which stocked varying frames with lenses which happened to suit you (which means that you would have to change opticians as your eyes deteriorated)! I guess it wouldn't matter for contact lenses, though. Maybe it's cultural; maybe it's a different system in Brazil. 

I think basically, you could check whether they know about whether they know the diopters of the lenses in their glasses (or of their contact lenses), you could ask them "Do you happen to know the strength of the lenses in your glasses/contact lenses?", and if they respond 'Yes', and give you an answer in dioptres, you can have a discussion about the dioptres of the lenses of glasses, or they may give you an answer in numbers, to which you could equally have an informal conversation. Chances are, they will probably say 'No', in which case you could explain it to them. They may seem genuinely interested, and may find out the next time they go to their opticians, but if they appear to be tiring of the conversation, then you can change the topic and you will know that it is not worth talking to that person specifically about such a topic.


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## Outsider

AngelEyes said:


> When you add the differences in languages [...]


Maybe that is part of the problem, too. In Portuguese, the word *dioptria* ("dioptre") is a technical term, but there's a more colloquial synonym, *grau*. As I understand it, Du_sud was hoping to find a suitable translation for _grau_. But because of the different cultural habits of Portuguese speakers and (many) English speakers this word is not trivial to translate. Apparently, there is no precise equivalent for it in English.


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