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There are only 11 lines in the eye chart. So why not 20/1-11?
-G — Preceding unsigned comment added by 70.27.113.62 ( talk) 01:33, 2 April 2012 (UTC)
I forgot to put the change's name when I added the Snellen card to the page. :)
Is is possible to test your own vision at home without going to an eye doctor? Or is special equipment needed? It seems like all you need is a paper with letters of a certain size, the right amount of light and a measuring tape. Perhaps some instructions on how to determine your visual acuity at home could be added. KannD86 ( talk) 14:31, 28 May 2009 (UTC)
I feel that the article has a lot more to say about visual acuity. Also it can be reorganized to structure it a little more. I will work on it in the following days if is there no objection.
Do you think it is important to mention the tecnique of measuring visual acuity? Because nothing is being mentioned about that, and also nothing is being mentioned of near visual acuity and pin hole. But the article is growing a lot by now....
Rafael Sepulveda 20:45, 23 December 2005 (UTC)
RE: "the average visual acuity of healthy eyes is 20/16 or 20/12". I'm wondering if we should clarify this a bit more. "Healthy" in what sense? No refractive error or free from disease? [split post - see below]
[split post - see above] Should we mention something to the extent that the best attainable vision is based on the spacing of photoreceptors? [split post - see below]
[split post - see above] You've alluded to it in the last sentence but perhaps we should state explicitly that having good visual acuity is not the same as having good vision. AED 22:17, 23 December 2005 (UTC)
I'm not pleased with the 'emmetropia' link to point to 'refractive error' page. Being this a complex subject (not a normal distribution graph, being that most people is lightly hyperope yet achieve 20/20, etc.) it should have it's own wikipedia page. What do you think?
I've added a lot of things... maybe a little polishing will be needed. :) Also, near vision definition and the all the standard optotypes used have to be added. Any more things I'm missing? Rafael Sepulveda 09:40, 26 December 2005 (UTC)
Do we have any references for maximum VA and/or average VA, aided or unaided, that we can include? I found one [1], but it doesn't state whether the students were aided or unaided. AED 05:57, 27 December 2005 (UTC)
A lot of the statements in the History section appears verbatim in Duane's. Can you rewrite or paraphrase some of these statements so we don't violate WP:COPY? Thanks! AED 00:20, 28 December 2005 (UTC)
the maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/15 (6/4.5)
the average visual acuity of healthy eyes is 20/16 or 20/12
I don't know much about visual acuity, but one of these (maybe both, of course) is almost certainly false.
Please include some explanation of how diopter measurments fit into this. I'm looking for a rough equivalent of the measurements used in this article and diopter measurements (which will have to be +/- becuase acuity does not determine myopia vs. hyperopia). Maybe a table with some standard acuity values (e.g. 20/20, 20/40, ... 20/400) and their equivalent diopter ranges? Kslays 15:55, 1 May 2006 (UTC)
What is -5.25 on the 20/20 scale?
Here is a table:
Dioptres | 20/something |
---|---|
-0.5 | 20/25 to 20/30 |
-1.0 | 20/30 to 20/50 |
-3.0 | 20/300 |
-4.0 | 20/400 |
-5.0 | 20/600 |
Dioptres | 20/something |
---|---|
+0.5 | 20/25 |
+1.0 | 20/40 |
+2.0 | 20/70 |
+3.0 | 20/100 |
+4.0 | 20/200 |
I understand this doesn't account for cylindrical (astigmatism), cataracts, or other problems, but a rough guide like this is very useful. - kslays 16:52, 19 June 2007 (UTC)
From the article:
A visual acuity of 20/20 is frequently described as meaning that a person can see detail from 20 feet away the same as a person with normal eyesight would see from the same distance. If a person has a visual acuity of 20/40, that person is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away.
What is meant by "normal eyesight"? 20/20? And if so, doesn't that make the first person meaningless, along the lines of a person with 20/20 vision can see as well as a person with 20/20 vision? Isn't there a less relative way of explaning this? Also, I don't think it's standard to use terms like "normal" in discussing physical conditions. Theshibboleth 05:37, 29 August 2006 (UTC)
I did a web search a few weeks ago and found that somewhere between 60 and 80 percent of Americans wear corrective eyewear (with the general consensus being about 2/3rds). Something is wrong with the definition of "normal" if 2/3rds of the population don't reach it. Saying that 20/20 is the LOW end of "normal vision" also does not fit with that statistic. Just because vision is correctable to what we now call 20/20 or better does not mean that the original definition was correct. And although eyesight deteriorates in one's later years, I have not heard that it goes on a steady decline starting from the age of 18 like hearing does. By that statistic, 2/3rds of the population is unable to resolve 1 minute of arc at 20 feet. Doesn't that start to sound like an unrealistic standard of "normal" eyesight? (I will still need to use glasses even if we make that able to resolve 1 minute of arc at 15 feet or even 10 feet, but I wanted to comment on the use of the term "normal" in the entry.) "Normal" people in this country do not have "normal" eyesight. Perhaps we can keep the 20/20 standard and change the expression to "good" eyesight, while 20/16 would be "excellent" and 20/12 "exceptional." Then we can call 20/40 or 20/60 "normal." 4.224.219.114 23:58, 29 June 2007 (UTC)
I think the phrase ""20-20 vision" refers to the distance in feet that objects separated by an angle of 1 arc minute can be distinguished as separate objects." is confused. If objects are separated by 1 arc minute (an angular measure) then distance shouldn't come into it. There's a problem with this definition. —Preceding unsigned comment added by 130.138.227.40 ( talk) 13:51, 31 October 2007 (UTC)
As many people are aware, a traditional test of visual acuity is the abilty to distinguish Mizar from Alcor, two stars in the big dipper. Given that the angle that separates them is about 12 minutes, what is the minimum visual acuity necessary to distinguish them (in terms of 20/x)? I was thinking about adding this to the Mizar article to quantify this "good vision" folktale once and for all. (Granted, it could be considered original research, but if it's only the result of some formula, it's probably not that bad, and I also really want to know.) 71.102.186.234 10:54, 26 November 2006 (UTC)
Ạẚ== 20/0 ==
Does 20/0 vision have any significant meaning? -- Brandon Dilbeck 04:52, 13 May 2007 (UTC)
The short answer is no. The long answer is that the fractional description of visual acuity is really a way of writing it, and not a real fraction. What this fraction means, as the article says, is that the first number, or the numerator, is the standard distance of the optotype. The second number, or the denominator, is the relative distance as it is seen by a "normal", emmetropic person.
So, 20/0 should mean that an optotype placed at 20 feet, is seen with the clarity as being right in contact with the eye. To me, as an ophthalmologist, that doesn't says anything practical given the optics of the eye or the light that should be reflected by the optotype. It's meaningless.
I Hope I make my point of view clear (because I'm not an english native speaker :) ). Rsepulveda 22:17, 14 July 2007 (UTC)
OK, so I was reading Mad Magazine (specifically the Monroe section), and I run into this part where a man using a magnifying glass says "Damn 10/10 vision!" But wouldn't this be like saying "Damn 20/20 vision" or "Damn 20/18 vision"??????? What is 10/10 vision?????? 131.191.64.130 ( talk) 02:59, 30 November 2007 (UTC)
Why does the last entry in the table in the History section link to a page about a football coach? Fixed.
I'd disagree, based on my experience in an ophthalmology department, that the LogMar isn't used clinically. It's about 50/50 LogMar/Snellen now. Also, it doesn't just refer to a different way of expressing Snellen measurements, but a LogMar chart is also a completely different way. Should I add this into the article? Andrew Jacklin 15:47, 4 December 2007 (UTC)
It appears that the system that includes "20/20" is roughly a measure of the MTF cutoff of the visual system. Why is 20 feet the selected focal distance? I suppose that's reasonable for reading from a chalkboard, but couldn't a farsighted person have 20/20 vision and simply be unable to focus within arms length? Similarly, couldn't a slightly nearsighted person have 20/20 vision but have less than that angular resolution when attempting to focus at infinity? 155.212.242.34 ( talk) 23:31, 21 February 2008 (UTC)
In the table of visual acuity scales, shouldn't the decimal corresponding to 20/30 and 6/9 be 0.67, rather than 0.63? -- Sakurambo 桜ん坊 12:23, 7 July 2008 (UTC)
On a foot scale, how would myopia (near-sightedness) and hyperopia (far-sightedness) be measured? Sorry for having to ask. DanMat6288 ( talk) 18:18, 21 October 2008 (UTC)
"the sensitivity of the interpretative faculty of the brain" is an early phrase in the summary. Processing appears to happen in the retina, whence signals are propagated to thebrain not depending on just one photoreceptor, but on several. "brain" should perhaps be changed to something including more of the nervous(?) system from retina to optic and other cortex. Or removing "of the brain" and discussing later where the interpretative faculty is implemented. This is an articlet hat looks good, and is going to be useful and interesting to many people. Midgley ( talk) 08:27, 14 May 2009 (UTC)
I've just edited this text for 1875:
Would Snellen, being Dutch, have worked in feet? Also, 20 feet is 6 metres, not 5. Isidore ( talk) 18:30, 29 December 2009 (UTC)
I think it would be more clear to say "the first number" and "the second number", since fractions aren't quite universal. —Preceding unsigned comment added by Sam Coskey ( talk • contribs) 02:03, 3 March 2010 (UTC)
In the History section the term VA is supposedly defined recursively with a reference to itself - this is probably incorrect.
Year | Event |
---|---|
.. | ... |
1861 | Franciscus Donders coined the term visual acuity to describe the “sharpness of vision” and defined it as the ratio between a subject's VA and a standard VA. |
.. | ... |
The following paragraph was in the main text under the Visual acuity testing in children section. I've moved it here because, whilst it may well be correct, I think it would be helpful if someone who knows more than I do about visual acuity could render it less technical and edit the main page as appropriate. Thanks! talk Giler 14:41, 20 May 2010 (UTC)
The article says that 20/10 is "superior", i.e. you can see at 20 feet what others can only see at 10. But isn't that merely hyperopia, farsightedness?? Doesn't that mean that if you have 20/10, you see worse up close, say 1/2?-- Dbjorck ( talk) 09:00, 12 September 2010 (UTC)
The statement "because it does not specify the nature of the problem with the lens" I think refers to the ability of all parts of the visual system, not just the crystalline lens. —Preceding unsigned comment added by 98.94.166.88 ( talk) 22:18, 8 January 2011 (UTC)
"The denominator indicates the size of the letters" I believe this statement is incorrect. How does the number 20 indicate the size of the letters? — Preceding unsigned comment added by 71.249.250.64 ( talk) 17:33, 18 August 2011 (UTC)
This article states that "20-20 is perfect vision" in the Physiology of visual acuity section. Later, in the Normal vision section, it states that "it is inaccurate to refer to 20/20 visual acuity as 'perfect' vision". I imagine that the latter is correct and that the former should be changed, but I don't really know much on this topic so I'll leave it for somebody else to change. — Preceding unsigned comment added by 27.32.110.51 ( talk) 05:35, 16 February 2012 (UTC)
The author states "In the expression, 20/20 vision, the numerator refers to the distance in feet between the subject and the chart. The denominator indicates the size of the letters, expressed in millimeters. The denominator does not measure the height of the letters. Rather, the denominator measures the distance of the separation of the lines that make up those letters."
then goes on to state-
"At 20 feet or 6 metres, a human eye with nominal performance is able to separate lines that are one arc minute apart (equivalent to lines that are spaced 1.75 mm apart."
How does the denominator ( the number 20) in the term 20/20 represent 1.75 millimeters?
I believe the latter statement "A visual acuity of 20/20 is frequently described as meaning that a person can see detail from 20 feet (6.1 m) away the same as a person with normal eyesight would see from 20 feet." to be true. — Preceding unsigned comment added by 71.249.250.64 ( talk) 22:28, 1 March 2012 (UTC)
There is something inconsistent in the introduction. Paragraph 6 says "The letters in the lowest line in the Snellen chart are composed of lines that are separated by a visual angle of one arc minute". In the figure of the Snellen chart, the lowest line is three lines below the 20/20 line. So if you can discern lines separated by one arc minute you are seeing much better than 20/20.
The next paragraph says " a human eye with nominal performance is able to separate lines that are one arc minute apart" so, nominal must be a lot better than 20/20. Then the next sentence says "A vision of 20/20 is considered nominal".
So, either normal human acuity can resolve 1 arc minute and the lowest line on the Snellen chart has features much less than 1 arc minute, or the lowest line on the Snellen chart has 1 arc minute features and 20/20 human has much less resolution than 1 arc minute. Constant314 ( talk) 02:15, 11 December 2012 (UTC)
How can the visual acuity in hawks be 20/2? Considering 20/20 is 60 seconds of arc and implies a 2.3mm diffraction limited aperture using the Rayleigh criterion then a 20/2 acuity implies a diffraction-limited aperture of around 23mm, for a 6 seconds of arc resolution. That's far bigger than even owl's eyes... impossible! Even yesterday I was looking at an eagle and her eyes don't have a much bigger pupil in the sun than ours, which are already near diffraction-limited. And her eyes are relatively small also, and therefore her pupil can't grow above 6 or 7mm at most, limiting acuity at best to 20/7 or so. — Preceding unsigned comment added by Rnbc ( talk • contribs) 21:02, 21 July 2013 (UTC)
Someone has changed a bunch of word to 'megaman'...? a quick look at the history shows the first instance is 'brain' > 'Megaman' — Preceding unsigned comment added by 143.65.196.20 ( talk) 16:14, 31 October 2013 (UTC)
Move in out motion produces pulse producing focusing problems. Focus in out to produce strength. XXX — Preceding unsigned comment added by 149.254.49.75 ( talk) 01:35, 30 January 2014 (UTC)
The preceding unsigned comment makes no sense. Whoever wrote it has no business writing or editing Wikipedia articles. rowley ( talk) 18:01, 11 December 2018 (UTC)
I am not an expert in this field, but while reading through the article the following caught my eye:
RE: Section 5.1, Legal Definitions, near the bottom of the section it gives this example of notation used in the documentation of visual acuity:
"So, distant visual acuity of 6/10 and 6/8 with pinhole in the right eye will be: DscOD 6/20 PH 6/8. Distant visual acuity of count fingers and 6/17 with pinhole in the left eye will be: DscOS CF PH 16/17."
Is it correct to write: DscOD 6/20 PH 6/8 -- why is it not 6/10? and the second: DscOS CF PH 16/17 -- why is it not 6/17?
If these notations are not a typo, and are correct as written, then it would seem an entry discussing how these numbers are derived from the raw data should be included.
Static1st ( talk) 13:39, 11 August 2015 (UTC)
Just want an answer. — Preceding unsigned comment added by 219.89.176.175 ( talk) 05:22, 19 November 2015 (UTC)
This article is so technical and full of jargon that an educated laymen cannot understand it. I have a degree in Computer Science from Cambridge University and am relatively technical in my general knowledge. Yet this article is beyond my ability to understand. This suggests most of the population will be unable to understand it. This article needs considerable clarification and explanation of the terms used.
-is this worthy of inclusion is procedure responses come to my talk page-thank you
/info/en/?search=File:Single_letter_relative_sizes_visual_acuity_measurement.jpg
PG D'Arcy ( talk) 14:49, 25 July 2018 (UTC)
The graph in the Physiology section is slightly misleading in that the acuity beyond 40° eccentricity is too low. It looks like it goes to zero when in fact it should remain at about 5%. The graph is taken from Hunziker, 2006. I will need to look for a more accurate graph. Strasburger ( talk) 15:59, 19 January 2020 (UTC)
This is the
talk page for discussing improvements to the
Visual acuity article. This is not a forum for general discussion of the article's subject. |
Article policies
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Find medical sources: Source guidelines · PubMed · Cochrane · DOAJ · Gale · OpenMD · ScienceDirect · Springer · Trip · Wiley · TWL |
This article is rated B-class on Wikipedia's
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Please help fix the broken anchors. You can remove this template after fixing the problems. |
Reporting errors |
There are only 11 lines in the eye chart. So why not 20/1-11?
-G — Preceding unsigned comment added by 70.27.113.62 ( talk) 01:33, 2 April 2012 (UTC)
I forgot to put the change's name when I added the Snellen card to the page. :)
Is is possible to test your own vision at home without going to an eye doctor? Or is special equipment needed? It seems like all you need is a paper with letters of a certain size, the right amount of light and a measuring tape. Perhaps some instructions on how to determine your visual acuity at home could be added. KannD86 ( talk) 14:31, 28 May 2009 (UTC)
I feel that the article has a lot more to say about visual acuity. Also it can be reorganized to structure it a little more. I will work on it in the following days if is there no objection.
Do you think it is important to mention the tecnique of measuring visual acuity? Because nothing is being mentioned about that, and also nothing is being mentioned of near visual acuity and pin hole. But the article is growing a lot by now....
Rafael Sepulveda 20:45, 23 December 2005 (UTC)
RE: "the average visual acuity of healthy eyes is 20/16 or 20/12". I'm wondering if we should clarify this a bit more. "Healthy" in what sense? No refractive error or free from disease? [split post - see below]
[split post - see above] Should we mention something to the extent that the best attainable vision is based on the spacing of photoreceptors? [split post - see below]
[split post - see above] You've alluded to it in the last sentence but perhaps we should state explicitly that having good visual acuity is not the same as having good vision. AED 22:17, 23 December 2005 (UTC)
I'm not pleased with the 'emmetropia' link to point to 'refractive error' page. Being this a complex subject (not a normal distribution graph, being that most people is lightly hyperope yet achieve 20/20, etc.) it should have it's own wikipedia page. What do you think?
I've added a lot of things... maybe a little polishing will be needed. :) Also, near vision definition and the all the standard optotypes used have to be added. Any more things I'm missing? Rafael Sepulveda 09:40, 26 December 2005 (UTC)
Do we have any references for maximum VA and/or average VA, aided or unaided, that we can include? I found one [1], but it doesn't state whether the students were aided or unaided. AED 05:57, 27 December 2005 (UTC)
A lot of the statements in the History section appears verbatim in Duane's. Can you rewrite or paraphrase some of these statements so we don't violate WP:COPY? Thanks! AED 00:20, 28 December 2005 (UTC)
the maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/15 (6/4.5)
the average visual acuity of healthy eyes is 20/16 or 20/12
I don't know much about visual acuity, but one of these (maybe both, of course) is almost certainly false.
Please include some explanation of how diopter measurments fit into this. I'm looking for a rough equivalent of the measurements used in this article and diopter measurements (which will have to be +/- becuase acuity does not determine myopia vs. hyperopia). Maybe a table with some standard acuity values (e.g. 20/20, 20/40, ... 20/400) and their equivalent diopter ranges? Kslays 15:55, 1 May 2006 (UTC)
What is -5.25 on the 20/20 scale?
Here is a table:
Dioptres | 20/something |
---|---|
-0.5 | 20/25 to 20/30 |
-1.0 | 20/30 to 20/50 |
-3.0 | 20/300 |
-4.0 | 20/400 |
-5.0 | 20/600 |
Dioptres | 20/something |
---|---|
+0.5 | 20/25 |
+1.0 | 20/40 |
+2.0 | 20/70 |
+3.0 | 20/100 |
+4.0 | 20/200 |
I understand this doesn't account for cylindrical (astigmatism), cataracts, or other problems, but a rough guide like this is very useful. - kslays 16:52, 19 June 2007 (UTC)
From the article:
A visual acuity of 20/20 is frequently described as meaning that a person can see detail from 20 feet away the same as a person with normal eyesight would see from the same distance. If a person has a visual acuity of 20/40, that person is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away.
What is meant by "normal eyesight"? 20/20? And if so, doesn't that make the first person meaningless, along the lines of a person with 20/20 vision can see as well as a person with 20/20 vision? Isn't there a less relative way of explaning this? Also, I don't think it's standard to use terms like "normal" in discussing physical conditions. Theshibboleth 05:37, 29 August 2006 (UTC)
I did a web search a few weeks ago and found that somewhere between 60 and 80 percent of Americans wear corrective eyewear (with the general consensus being about 2/3rds). Something is wrong with the definition of "normal" if 2/3rds of the population don't reach it. Saying that 20/20 is the LOW end of "normal vision" also does not fit with that statistic. Just because vision is correctable to what we now call 20/20 or better does not mean that the original definition was correct. And although eyesight deteriorates in one's later years, I have not heard that it goes on a steady decline starting from the age of 18 like hearing does. By that statistic, 2/3rds of the population is unable to resolve 1 minute of arc at 20 feet. Doesn't that start to sound like an unrealistic standard of "normal" eyesight? (I will still need to use glasses even if we make that able to resolve 1 minute of arc at 15 feet or even 10 feet, but I wanted to comment on the use of the term "normal" in the entry.) "Normal" people in this country do not have "normal" eyesight. Perhaps we can keep the 20/20 standard and change the expression to "good" eyesight, while 20/16 would be "excellent" and 20/12 "exceptional." Then we can call 20/40 or 20/60 "normal." 4.224.219.114 23:58, 29 June 2007 (UTC)
I think the phrase ""20-20 vision" refers to the distance in feet that objects separated by an angle of 1 arc minute can be distinguished as separate objects." is confused. If objects are separated by 1 arc minute (an angular measure) then distance shouldn't come into it. There's a problem with this definition. —Preceding unsigned comment added by 130.138.227.40 ( talk) 13:51, 31 October 2007 (UTC)
As many people are aware, a traditional test of visual acuity is the abilty to distinguish Mizar from Alcor, two stars in the big dipper. Given that the angle that separates them is about 12 minutes, what is the minimum visual acuity necessary to distinguish them (in terms of 20/x)? I was thinking about adding this to the Mizar article to quantify this "good vision" folktale once and for all. (Granted, it could be considered original research, but if it's only the result of some formula, it's probably not that bad, and I also really want to know.) 71.102.186.234 10:54, 26 November 2006 (UTC)
Ạẚ== 20/0 ==
Does 20/0 vision have any significant meaning? -- Brandon Dilbeck 04:52, 13 May 2007 (UTC)
The short answer is no. The long answer is that the fractional description of visual acuity is really a way of writing it, and not a real fraction. What this fraction means, as the article says, is that the first number, or the numerator, is the standard distance of the optotype. The second number, or the denominator, is the relative distance as it is seen by a "normal", emmetropic person.
So, 20/0 should mean that an optotype placed at 20 feet, is seen with the clarity as being right in contact with the eye. To me, as an ophthalmologist, that doesn't says anything practical given the optics of the eye or the light that should be reflected by the optotype. It's meaningless.
I Hope I make my point of view clear (because I'm not an english native speaker :) ). Rsepulveda 22:17, 14 July 2007 (UTC)
OK, so I was reading Mad Magazine (specifically the Monroe section), and I run into this part where a man using a magnifying glass says "Damn 10/10 vision!" But wouldn't this be like saying "Damn 20/20 vision" or "Damn 20/18 vision"??????? What is 10/10 vision?????? 131.191.64.130 ( talk) 02:59, 30 November 2007 (UTC)
Why does the last entry in the table in the History section link to a page about a football coach? Fixed.
I'd disagree, based on my experience in an ophthalmology department, that the LogMar isn't used clinically. It's about 50/50 LogMar/Snellen now. Also, it doesn't just refer to a different way of expressing Snellen measurements, but a LogMar chart is also a completely different way. Should I add this into the article? Andrew Jacklin 15:47, 4 December 2007 (UTC)
It appears that the system that includes "20/20" is roughly a measure of the MTF cutoff of the visual system. Why is 20 feet the selected focal distance? I suppose that's reasonable for reading from a chalkboard, but couldn't a farsighted person have 20/20 vision and simply be unable to focus within arms length? Similarly, couldn't a slightly nearsighted person have 20/20 vision but have less than that angular resolution when attempting to focus at infinity? 155.212.242.34 ( talk) 23:31, 21 February 2008 (UTC)
In the table of visual acuity scales, shouldn't the decimal corresponding to 20/30 and 6/9 be 0.67, rather than 0.63? -- Sakurambo 桜ん坊 12:23, 7 July 2008 (UTC)
On a foot scale, how would myopia (near-sightedness) and hyperopia (far-sightedness) be measured? Sorry for having to ask. DanMat6288 ( talk) 18:18, 21 October 2008 (UTC)
"the sensitivity of the interpretative faculty of the brain" is an early phrase in the summary. Processing appears to happen in the retina, whence signals are propagated to thebrain not depending on just one photoreceptor, but on several. "brain" should perhaps be changed to something including more of the nervous(?) system from retina to optic and other cortex. Or removing "of the brain" and discussing later where the interpretative faculty is implemented. This is an articlet hat looks good, and is going to be useful and interesting to many people. Midgley ( talk) 08:27, 14 May 2009 (UTC)
I've just edited this text for 1875:
Would Snellen, being Dutch, have worked in feet? Also, 20 feet is 6 metres, not 5. Isidore ( talk) 18:30, 29 December 2009 (UTC)
I think it would be more clear to say "the first number" and "the second number", since fractions aren't quite universal. —Preceding unsigned comment added by Sam Coskey ( talk • contribs) 02:03, 3 March 2010 (UTC)
In the History section the term VA is supposedly defined recursively with a reference to itself - this is probably incorrect.
Year | Event |
---|---|
.. | ... |
1861 | Franciscus Donders coined the term visual acuity to describe the “sharpness of vision” and defined it as the ratio between a subject's VA and a standard VA. |
.. | ... |
The following paragraph was in the main text under the Visual acuity testing in children section. I've moved it here because, whilst it may well be correct, I think it would be helpful if someone who knows more than I do about visual acuity could render it less technical and edit the main page as appropriate. Thanks! talk Giler 14:41, 20 May 2010 (UTC)
The article says that 20/10 is "superior", i.e. you can see at 20 feet what others can only see at 10. But isn't that merely hyperopia, farsightedness?? Doesn't that mean that if you have 20/10, you see worse up close, say 1/2?-- Dbjorck ( talk) 09:00, 12 September 2010 (UTC)
The statement "because it does not specify the nature of the problem with the lens" I think refers to the ability of all parts of the visual system, not just the crystalline lens. —Preceding unsigned comment added by 98.94.166.88 ( talk) 22:18, 8 January 2011 (UTC)
"The denominator indicates the size of the letters" I believe this statement is incorrect. How does the number 20 indicate the size of the letters? — Preceding unsigned comment added by 71.249.250.64 ( talk) 17:33, 18 August 2011 (UTC)
This article states that "20-20 is perfect vision" in the Physiology of visual acuity section. Later, in the Normal vision section, it states that "it is inaccurate to refer to 20/20 visual acuity as 'perfect' vision". I imagine that the latter is correct and that the former should be changed, but I don't really know much on this topic so I'll leave it for somebody else to change. — Preceding unsigned comment added by 27.32.110.51 ( talk) 05:35, 16 February 2012 (UTC)
The author states "In the expression, 20/20 vision, the numerator refers to the distance in feet between the subject and the chart. The denominator indicates the size of the letters, expressed in millimeters. The denominator does not measure the height of the letters. Rather, the denominator measures the distance of the separation of the lines that make up those letters."
then goes on to state-
"At 20 feet or 6 metres, a human eye with nominal performance is able to separate lines that are one arc minute apart (equivalent to lines that are spaced 1.75 mm apart."
How does the denominator ( the number 20) in the term 20/20 represent 1.75 millimeters?
I believe the latter statement "A visual acuity of 20/20 is frequently described as meaning that a person can see detail from 20 feet (6.1 m) away the same as a person with normal eyesight would see from 20 feet." to be true. — Preceding unsigned comment added by 71.249.250.64 ( talk) 22:28, 1 March 2012 (UTC)
There is something inconsistent in the introduction. Paragraph 6 says "The letters in the lowest line in the Snellen chart are composed of lines that are separated by a visual angle of one arc minute". In the figure of the Snellen chart, the lowest line is three lines below the 20/20 line. So if you can discern lines separated by one arc minute you are seeing much better than 20/20.
The next paragraph says " a human eye with nominal performance is able to separate lines that are one arc minute apart" so, nominal must be a lot better than 20/20. Then the next sentence says "A vision of 20/20 is considered nominal".
So, either normal human acuity can resolve 1 arc minute and the lowest line on the Snellen chart has features much less than 1 arc minute, or the lowest line on the Snellen chart has 1 arc minute features and 20/20 human has much less resolution than 1 arc minute. Constant314 ( talk) 02:15, 11 December 2012 (UTC)
How can the visual acuity in hawks be 20/2? Considering 20/20 is 60 seconds of arc and implies a 2.3mm diffraction limited aperture using the Rayleigh criterion then a 20/2 acuity implies a diffraction-limited aperture of around 23mm, for a 6 seconds of arc resolution. That's far bigger than even owl's eyes... impossible! Even yesterday I was looking at an eagle and her eyes don't have a much bigger pupil in the sun than ours, which are already near diffraction-limited. And her eyes are relatively small also, and therefore her pupil can't grow above 6 or 7mm at most, limiting acuity at best to 20/7 or so. — Preceding unsigned comment added by Rnbc ( talk • contribs) 21:02, 21 July 2013 (UTC)
Someone has changed a bunch of word to 'megaman'...? a quick look at the history shows the first instance is 'brain' > 'Megaman' — Preceding unsigned comment added by 143.65.196.20 ( talk) 16:14, 31 October 2013 (UTC)
Move in out motion produces pulse producing focusing problems. Focus in out to produce strength. XXX — Preceding unsigned comment added by 149.254.49.75 ( talk) 01:35, 30 January 2014 (UTC)
The preceding unsigned comment makes no sense. Whoever wrote it has no business writing or editing Wikipedia articles. rowley ( talk) 18:01, 11 December 2018 (UTC)
I am not an expert in this field, but while reading through the article the following caught my eye:
RE: Section 5.1, Legal Definitions, near the bottom of the section it gives this example of notation used in the documentation of visual acuity:
"So, distant visual acuity of 6/10 and 6/8 with pinhole in the right eye will be: DscOD 6/20 PH 6/8. Distant visual acuity of count fingers and 6/17 with pinhole in the left eye will be: DscOS CF PH 16/17."
Is it correct to write: DscOD 6/20 PH 6/8 -- why is it not 6/10? and the second: DscOS CF PH 16/17 -- why is it not 6/17?
If these notations are not a typo, and are correct as written, then it would seem an entry discussing how these numbers are derived from the raw data should be included.
Static1st ( talk) 13:39, 11 August 2015 (UTC)
Just want an answer. — Preceding unsigned comment added by 219.89.176.175 ( talk) 05:22, 19 November 2015 (UTC)
This article is so technical and full of jargon that an educated laymen cannot understand it. I have a degree in Computer Science from Cambridge University and am relatively technical in my general knowledge. Yet this article is beyond my ability to understand. This suggests most of the population will be unable to understand it. This article needs considerable clarification and explanation of the terms used.
-is this worthy of inclusion is procedure responses come to my talk page-thank you
/info/en/?search=File:Single_letter_relative_sizes_visual_acuity_measurement.jpg
PG D'Arcy ( talk) 14:49, 25 July 2018 (UTC)
The graph in the Physiology section is slightly misleading in that the acuity beyond 40° eccentricity is too low. It looks like it goes to zero when in fact it should remain at about 5%. The graph is taken from Hunziker, 2006. I will need to look for a more accurate graph. Strasburger ( talk) 15:59, 19 January 2020 (UTC)