Eyesight Scales 1.0 vs 5.0 Explained | Generated by AI
Ah, I see — you’re now asking about “1.0 eyesight” or “5.0 eyesight”, which is different from the diopter (度数 D) measure we just discussed. Let’s clear up the two systems:
1. The Two Systems
- Diopters (D, 度数) → used in prescriptions, e.g. −4.00 D for 400° myopia. It directly relates to the focal length of your eye.
- Visual acuity (视力表, like 1.0, 5.0, 20/20) → this is what you get on a vision chart test, and it measures how small details you can resolve at a given distance.
They’re related but not the same.
2. Visual Acuity “1.0”
- 1.0 eyesight in China/Japan scale ≈ 20/20 in Snellen (Western) scale
- That means: at 5 m (or 20 feet), you can read the same line that a person with “normal” vision can.
- This corresponds to perfect or standard normal vision.
- It doesn’t mean “you can only see 5 m away”; it means you can resolve a certain level of detail at 5 m. In practice, you can still see infinity clearly, just like an emmetropic (0D) eye.
3. Visual Acuity “5.0”
This sounds like the Chinese decimal chart system:
- 5.0 = 1.0 (20/20)
- 5.1 = 1.1 (20/17)
- 5.2 = 1.2 (20/16)
- … up to 5.3, 5.4, 5.5 which correspond to better-than-normal vision (20/12 or sharper).
So if you say 5.0 eyesight, that’s normal vision (20/20). If you say 1.0 eyesight, that also means normal vision (20/20), just another scale.
4. The Key Difference
- Visual acuity (1.0, 5.0, 20/20) → “How small letters/details can you resolve at a given test distance.”
- Diopters (D) → “At what maximum distance can you see clearly without correction.”
They’re not directly interchangeable. Someone can have −4.00 D myopia (25 cm far point) but still test at 1.0 (20/20) on a chart with glasses on.
👉 So:
- 1.0 eyesight = normal 20/20 vision (clear to infinity).
- 5.0 eyesight (Chinese scale) = also normal 20/20.
- If you have better than 5.0 (e.g. 5.2, 5.3), you can see sharper than average — like “20/15” or “20/12”.
Do you want me to show you a mapping table between diopters (近视度数) and eyesight values (like 5.0, 4.8, 4.6)? That’ll connect the two systems directly.