I am from Mainland China and I find that the way we describe the eye prescription is totally different from English because we use a different metric system. If someone asks me "What's your eyesight?" or "How strong are your glasses?" I don't know how to answer it.

I googled the answer and find that I may answer like "I’m nearsighted with -3.0 diopters in my left eye." But diopter seems be a big word, I can't even find it in longman https://www.ldoceonline.com/spellcheck/english/?q=diopter . So I am wondering do people really use it ?

I also see the answer like I am 20/100 vision. After google that meaning I have a rough idea what that means. But still it seems too complicated to me. Do people really use that ?

The comment from @FumbleFingers made me realize I need to explain why I had such question in the first place. Because more that 90% of China’s youth suffer from near-sightedness, check here and here, it has become a common question to ask others. It is a small talk to connect people.

BTW, in China it is really simple. The biggest E on the top is 0.1 (the old system) or 4.0(the new system). It means the worst. The bottom line is 2.0 or 5.3, the best.

eye chart


4 Answers 4


One of my friends in states answered my question the other day. I post her answer here. From the answers and comments I got I start to realize maybe this is another culture difference I never think of before.

How is your eyesight would be the correct way to ask, but we do not ask other people that question unless there is a specific need to ask.

No one would ever ask someone here "What is your eyesight". So forget that phrase entirely. If someone sees you are having trouble reading, they might ask if they need reading glasses. We do not ever have any conversation in general about eyesight. Someone might say, "I have to get a new prescription for my glasses today so I will be at the eye doctor's all afternoon", to tell what they are doing. We would only ask if the conversation went to the topic of two people with problems wanting to talk about maybe who their doctor is or where they buy their glasses or might exclaim, "Oh, I can hardly see this. I might need a new prescription."

Rarely would you ever ask if someone is near-sighted or far-sighted. I have never asked anyone that in my life nor have they asked me. You certainly would never talk about what your prescription actually is about the diopter or whatever the word was that you used. We would never in any case at all go into the technicalities of our prescription because none of us know it. We just don't talk about it here and if someone tried to have a chatty conversation with you , that would never be the topic.

  • 1
    This is clearly the best answer to your question. Just a shame you can't upvote or accept it (because you posted it yourself). I would just note that most Anglophones are familiar with the expression 20/20 vision - but in my experience people usually understand it to mean [near-]perfect eyesight, rather than simply "average", and it's very uncommon to hear that format used with any other numbers. Commented Oct 11, 2021 at 11:45

I suspect the answer you're looking for is "20/20 vision," or the average level of vision. An article from the American Academy of Ophthalmology offers this explanation:

“A person with 20/20 vision can see what an average individual can see on an eye chart when they are standing 20 feet away,” says Dr. McKinney. McKinney is an ophthalmologist and glaucoma specialist at Eye Health Northwest, Oregon City, Ore.


For example, if you have 20/30 vision, it means your vision is worse than average. Twenty feet away, you can read letters most people see from 30 feet.

But 20/20 vision is not perfect vision. A person can have 20/15 vision, which is sharper than average. If you have 20/15 vision, you can see a line in the eye chart at 20 feet that the average person can only see when they are 15 feet away. The goal of glasses or contacts is to bring a person’s vision to 20/20.

If you look at the article you'll also find it features a chart similar to the one you have posted.

This phrase is absolutely commonly used and understood, enough so to appear in aphorisms like "hindsight is 20/20," meaning "it is easy to see what one should have done after the fact." It is read "twenty twenty."

If I'm not mistaken, metric countries often use 6/6 vision, with meters, rather than feet, in the same way.

  • Thanks for the expression "hindsight is 20/20" I didn't know that. Commented Oct 11, 2021 at 5:12

"What is your eyesight?" is asking for a description of vision, of the working of the human eye. A suitable answer would be "Eyesight is the ability to perceive light".

"HOW is your eyesight?", or more commonly "How good/strong are your eyes/glasses?" is asking on the quality of your sight, as compared to an average human. The normal answer would be "Good", or "Fine as long as I wear my glasses", or "I'm quite nearsighted". Or of course "None of your business!!", because it is a very personal question.


If someone asks me "What's your eyesight?" I don't know how to answer it.

"What's your eyesight?" is not idiomatic in the meaning you seem to be proposing.

The answer to that question is "My eyesight is my power or faculty of seeing; it is my sight."

If someone asks me "How strong are your glasses?" I don't know how to answer it.

The answer is "Quite strong."

If the context is about diopters or the person asking sells glasses or tests eyes, then diopters is fine.

  • Thanks for answering my question. But when I ask "What's your eyesight?" I just asked the question literally. I did not propose any other meaning. So your answer made wonder did I say my question clearly ? Commented Oct 9, 2021 at 2:29
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    @Qiulang 邱朗 The first comment above is 'It's just not the kind of question Anglophones would normally ask' (which I think would be better stated 'This sounds very unnatural to a native speaker'. "How are your eyes?" or "How is your eyesight [now]?" are far more natural-sounding. And most people have at best only a fleeting memory of the word 'dioptres': they would usually answer "It's getting worse; I need to see the optician soon" or "I need very strong lenses" or "I can't see at all without my glasses" (or "Fine, thanks") etc. Commented Oct 9, 2021 at 10:06
  • So you were saying "how is your eyesight" is far more natural than "what is your eyesight", right ? Interestingly, but not related to my question is that for our non-native speaker we always say "how do call it" instead of "what do you call it" when asking a name for something. lol Commented Oct 9, 2021 at 10:18
  • @EdwinAshworth - mostly we don't talk about our eyesight. Why would we? If a stranger on a bus said, as small talk, 'How's your eyesight?', I would think it very odd indeed, and wonder if he was trying to sell spectacles or laser surgery. Likewise other medical things such as blood pressure, whether I have varicose veins, etc. Commented Oct 9, 2021 at 18:19
  • @Michael Harvey I find that as I get older, I'm having rather more brief, solicitous discussions about eyesight with people in the church say. Not about the need for stronger glasses, but about more serious problems. Commented Oct 10, 2021 at 16:58

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