Blind and Visually Impaired Community
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Why do Americans express a person's visual ability in such a weird way? (self.Blind)
submitted by KingWithoutClothes
No offense but I've now been a member of this sub for a long time and I'm still so confused. When Americans have "perfect" vision, as in, they are fighter jet pilots, they call it 20/20. Many people on this sub say stuff like: "I currently have 10/80" or "my visual ability is 45/350". What on Earth does that even mean? Does the left number stand for the left eye and the right number for the right eye? And if so, what do they represent?? Or am I supposed to make some kind of calculation, like 10/80 = 1/8?
In my country we simply express visual ability with percentages. For example I have roughly 2% vision on my right eye. This seems so much easier. Everyone knows how much 2% is and people can at least roughly imagine what it might be like to have 2% vision. If someone tells me: "my vision is 60/840" that tells me absolutely nothing.
In my country we simply express visual ability with percentages. For example I have roughly 2% vision on my right eye. This seems so much easier. Everyone knows how much 2% is and people can at least roughly imagine what it might be like to have 2% vision. If someone tells me: "my vision is 60/840" that tells me absolutely nothing.
WeHaveNoNeed 11 points 3y ago
Because it isn't a weird way. It means you see at (numerator) feet how someone with "perfect" vision sees at (denominator) feet. Except in Europe apparently we use 6/6 notation instead, using metres instead of feet.
So, 10/20 means that you can see as well at ten feet as someone with perfect sight can see at 20 feet.
So, 10/20 means that you can see as well at ten feet as someone with perfect sight can see at 20 feet.
noaimpara 1 points 3y ago
I still don’t get it, my last two braincells are so confused. So what does 200/20 mean? Thank
awesomesaucesaywhat 1 points 3y ago
At 200/20 the main person (you?) can see at 200 feet what a person with good vision could see at 20 feet.
noaimpara 2 points 3y ago
Not me haha I have no idea what my visual ability is in English. 20/200 is the threshold to be considered legally blind in some places I’ve heard.
Maybe it’s the phrasing, maybe it’s just my brain refusing to cooperate at 3:30AM, but I genuinely don’t get what that means.
Maybe it’s the phrasing, maybe it’s just my brain refusing to cooperate at 3:30AM, but I genuinely don’t get what that means.
awesomesaucesaywhat 2 points 3y ago
Haha okay, let’s try again.
If person a (bad vision) stands 20 ft away from a sign, they will be able to see the same amount of detail as person b (normal vision) who is standing 200 feet away.
I agree, it’s a confusing system.
If person a (bad vision) stands 20 ft away from a sign, they will be able to see the same amount of detail as person b (normal vision) who is standing 200 feet away.
I agree, it’s a confusing system.
-shacklebolt- 9 points 3y ago
https://en.wikipedia.org/wiki/Visual_acuity#Expression
This is not at all a uniquely American thing.
This is not at all a uniquely American thing.
KillerLag 1 points 3y ago
May I ask what country you are in? I've never heard of a country that uses only a percentage. I've heard it in feet and in metric (20/20 and 6/6), and LogMAR, but never in percentage.
The thing is, if they translate 20/20 to a percentage, that doesn't tell you anything. Because if 20/20 is 100%, then 20/25 is 80% vision. But 20/25 is an extremely minor loss in vision, most people wouldn't even notice the difference. And the system goes down to CF (Count Fingers), HM (Hand Movement) and LP (Light Perception).
The percentage also doesn't take into account field loss. I've met clients who have tunnel vision, so they have an extremely tiny visual field (like looking through a straw), but their visual acuity is still 20/20. What percentage would that be?
EDIT: Checking your history, I think you are Swiss.
https://www.snablind.ch/blindness-/-visual-impairment
This is cited on the website Swiss National Assocation of and for the Blind - "The World Health Organisation (WHO) defines blindness as having five percent vision or less (visual acuity less than 0.05%)"
However, I think they may have been quoting an old report or something. The WHO website now uses metric acuity measurements.
https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment
The International Classification of Diseases 11 (2018) classifies vision impairment into two groups, distance and near presenting vision impairment.
Distance vision impairment:
Mild – presenting visual acuity worse than 6/12
Moderate – presenting visual acuity worse than 6/18
Severe – presenting visual acuity worse than 6/60
Blindness – presenting visual acuity worse than 3/60
The thing is, if they translate 20/20 to a percentage, that doesn't tell you anything. Because if 20/20 is 100%, then 20/25 is 80% vision. But 20/25 is an extremely minor loss in vision, most people wouldn't even notice the difference. And the system goes down to CF (Count Fingers), HM (Hand Movement) and LP (Light Perception).
The percentage also doesn't take into account field loss. I've met clients who have tunnel vision, so they have an extremely tiny visual field (like looking through a straw), but their visual acuity is still 20/20. What percentage would that be?
EDIT: Checking your history, I think you are Swiss.
https://www.snablind.ch/blindness-/-visual-impairment
This is cited on the website Swiss National Assocation of and for the Blind - "The World Health Organisation (WHO) defines blindness as having five percent vision or less (visual acuity less than 0.05%)"
However, I think they may have been quoting an old report or something. The WHO website now uses metric acuity measurements.
https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment
The International Classification of Diseases 11 (2018) classifies vision impairment into two groups, distance and near presenting vision impairment.
Distance vision impairment:
Mild – presenting visual acuity worse than 6/12
Moderate – presenting visual acuity worse than 6/18
Severe – presenting visual acuity worse than 6/60
Blindness – presenting visual acuity worse than 3/60
noaimpara 1 points 3y ago
I’m also so confused. Where I live, perfect vision is 10/10 (as in ten out of ten) and then it goes down from there and can get into negatives. I have no idea how to translate my visual ability thing into English because I really don’t understand the logic of it no matter how many times it’s explained to me.
Jeanbean76 1 points 3y ago
2% of what? Perfect vision? What if you begin with poor sight because your parents didn't know when enough children (I'm #5) with bad eyes was enough. If you start with less than 100%, than 2% is not what one would assume. Please educate me if incorrect.
noaimpara 1 points 3y ago
It’s fair to assume they mean 100% is perfect vision.
Prefect316 -4 points 3y ago
Same reason we do inches and feet instead of the metric system. We're dumb!
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