I'm Korean, and here, when we talk about eyesight, we say "My left eye is 1.5 and right eye is 1.0. The smaller the number is, the worse the eye is. Ex) 2.0 - perfect / 0.1 - too bad. need glasses.

And I wonder how to say 1.2 in English way. I googled and it shows that 20/20 means 1.0. However, what I'd like to know is 1.2 in English way.

Sorry about my broken English. It's my best though.

  • 3
    This question isn't so much about the English language as it is about unit conversions.
    – zerohedge
    Apr 20 '15 at 11:33
  • 3
    I didn't find an obvious answer to this in a Google search. Even though it's more about units than English, I'm voting to leave it open since there are cultural and idiomatic aspects.
    – Adam Haun
    Apr 20 '15 at 14:12
  • 4
    The term for these types of measurements is "visual acuity" and there are several different scales: en.wikipedia.org/wiki/Visual_acuity#Expression The US uses the foot scale and it sounds like Korea uses the decimal scale. Try to read that section of the Wikipedia article. It may answer your question. If some of the English is difficult to understand, we can help explain it - just post another question about the part you don't understand.
    – ColleenV
    Apr 20 '15 at 17:11
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    I'm voting to close this question as off-topic because visual acuity scales are different in different regions and not necessarily different between English and non-English speaking areas. In my opinion, this isn't a question about English as it is currently written. I think it is similar to asking for a conversion between metric and imperial units.
    – ColleenV
    Apr 20 '15 at 17:15
  • 1
    In American English, the usual way of expressing the quality of a person's eyesight is by comparing how far away they can see the same size letters that a person with 20/20 vision can see from 20 feet away. Usually these numbers are rounded. For example: 20/10 and 20/15 are very good; 20/20 is considered normal or good; 20/25 and 20/30 are below average but do not indicate a need for glasses; 20/40, 20/50, and 20/60 are poor but correctable (with glasses); 20/200 or 20/400 are very poor.
    – Jasper
    Aug 18 '15 at 18:12

I hear something like the following occasionally and it seems most natural to me as an AmE native:

My eyesight is 20/20.

I have 20/20 eyesight.

He has 20/20 vision.

"20/20" is a common phrase, but any measurement other than 20/20 needs a bit of qualification.

I had my vision tested and seems I have 20/80 eyesight.

Saying something like

Her vision is 20/80

will have the listener/reader searching for a bit of context unless you're already talking about eyesight.

I don't hear the decimal notation at all and it would probably confuse at least an AmE speaker.


In addition to ultrasawblade's answer, I do hear decimals used frequently (I'm in US); however, I think this should depend on your audience. If you're talking casually with someone who maybe isn't as exposed to the world of eye issues (my entire family has eye problems, so we talk about it a lot), then using "20/80" or similar is best. But I use "-3.25" or ".5" often as well, and that's all my optometrist uses when talking to me. Judge your audience.

  • 1
    The decimal numbers are the diopter of the lens needed to correct someone's eyesight. I don't think it corresponds to the Korean model.
    – mkennedy
    Nov 16 '15 at 19:55

This should be a comment, but I don't have the rep on this site to comment. Google "diopter" and "glasses", and you will many sites with the information you need. (Diopter is the reciprocal of the focal length, in meters.)

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