Japanese optometric system (2025)

Hi,

A Japanese friend of mine was telling me about her myopia and we were trying to compare how myopic we are but it turned out that the French and Japanese measuring systems are completely different.

She told me that she has:
右0.1 左1.2
But was unable to explain what those numbers are.

She says her eyesight is terribly bad, which surprises me, because in our system those are quite good numbers. To give you an example, I'm not very myopic and my numbers are:
Right: 1.5 (meaning that my eyesight is 8.5/10)
Left: 1.0 (or 9/10)

Does anyone know how the Japanese system works?

Thank you for your help. It looks like the American system is very different too...

carp3 said:

I am not sure how you measure in France.

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In France, 10/10 is perfect. If you are myopic the first number goes down. For example, 9/10 is a slight myopia, while 1/10 is quasi-blindness.
A person with eyes a little too "focused" would get a 11/10.

Nobody's asking the US system.

Pot-Bouille, in the Japanese system, the max rate is 2.0. See how your friend has poor eyesight on her right eye. But her left eye is much better.

Thank you for your help, Frequency.
I looked around different wiki pages and found many technical explanations that made no sense to my poor non-scientific mind.
The only thing I got for sure is that Japan is one of the only countries that use the Landolt chart and that France is one of the only country to measure eyesight with a 10 grade system.

To go back to my initial question, my friend sent me a link to a わかりやすい page: http://homepage1.nifty.com/tadahiko/ZOKI/ZOKI-171.HTML

I found this part especially helpful:
◆小学校や中学校で、裸眼視力を測定する場合、最近はＡ、Ｂ、Ｃ、Ｄの４段階で記録されることが多いです。

　　Ａ：1.0 以上……教室での勉強に支障なし。
　　Ｂ：0.7～0.9……教室での勉強に不便なことがある。
　　Ｃ：0.3～0.6……教室での勉強に不便なことが多い。
　　Ｄ：0.2 以下……教室での勉強に不便あり。
​

Pot-Bouille said:

I looked around different wiki pages and found many technical explanations that made no sense to my poor non-scientific mind.

Click to expand...

Me too. lol I checked Wikipedia and I've found the difficult standard. I think technicians use it.

I asked my workmate who sits in front of me. He has started using an eyeglass when his eyesight marked around 0.5. That fits category C, doesn't it? The workmate now has eyesight of 0.0x, and he has stopped measuring the too-poor eyesight because he feels it's useless. Eyesight of less than 0.1 like his, it is called 強度近視. By the way, I think that C and D may suggest 近視－目が悪い, maybe!

Here's a page with a conversion table: Conversion Table for Representation of Visual Acuity | NIDEK CO.,LTD.
The Japanese system is labeled "decimal."

I don't think the Japanese system measures farsighted vs nearsighted, I think it's just an accuracy test, i.e. your score on a simple "tell me what these letters are" test.
1.0 is average, and higher than that is good eyesight while less is poor eyesight.