I just dont see it *blink*

Discussion in 'General Discussion' started by zed, Jan 18, 2018.

  1. zed

    zed
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    I will state this for the 20th time (at least)
    20/20 is not normal, 20/20 vision is bad. Normal is more like 20/15

    from wiki
    edit: and yes 28" for a 4k monitor is too small (I have a 28" 4k monitor which I curse for being too small), I would get at least a 34" for 4k
     
  2. CSI PC

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    Hmm.
    But pilots both commercial and military must be able to achieve 20/20 vision, albeit allowed with the aid of glasses but only up to a certain threshold and depends upon role.
    So not sure how one can say 20/20 vision is bad.
     
  3. rcf

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    Well, that's terrible vision by aboriginal standards.
     
  4. zed

    zed
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    because if you have 20/20 vision (with glasses or not) and are not a pensioner then your eyesight is worse than average.
     
  5. Kyyla

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    Depends on age really. Many people also walk around with less than 20/20 vision and don't bother to wear glasses.
     
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  6. BRiT

    BRiT (╯°□°)╯
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    Yes, that behavior is very normal and typical.
     
  7. DmitryKo

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    You've omitted an important part of your wiki quote, it should actually read 'in young humans, the average visual acuity ... is approximately 6/5 to 6/4' - obviously not everyone is a 12-17 year old teen with 20/15 vision, and 20/20 (logMAR 0.0) vision is an expected average across the entire population.

    It's 'normal' in the sense of medical statistics - as the mode (peak) of the probability distribution within a reference range for healthy humans.
     
    #7 DmitryKo, Jan 22, 2018
    Last edited: Jan 23, 2018
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  8. zed

    zed
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    Incorrect as I wrote before 20/20 is normal if you're a pensioner
    https://www.livestrong.com/article/250815-2070-eye-exam-results/
    you could be correct if the mean (though median is better for this) age for a human is in their 60/70s but it aint its a bit lower (I think 35 from memory though this will vary by country)

    (its an anecdote so nearly worthless but I expect many others are in the same boat) Myself, Im in my 40s,
    I can't even 'read' the E at the top without my glasses (thus apparently I'm legally blind) but sticking on my glasses I can easily read a couple lines below 20/20.

    Next time you're in an optometrists (perhaps a doctors as well) have a look at the chart, you may be shocked at having better than 20/20 vision. And all the people around you also have better than 'normal' vision.
    Now why is that? The majority of ppl can't have better than normal vision can they
    [​IMG]
     
  9. zed

    zed
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    you at home might want to give this a test
    https://www.provisu.ch/images/PDF/Snellenchart_en.pdf
    OK it most likely won't be taken under lab conditions but it should give you a rough idea,

    NOTE : even here they have false information (though I assume/hope the test method is correct)
    FFS, 20:20 is not optimal cause its possible (not only possible but likely) to do better, though I see this is a swiss site, perhaps they misunderstand the word optimal
     
  10. CSI PC

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    I am confused.
    Are you saying 20/20 is poor eyesight or that generally it is not the norm?
    Because like I said you cannot become a commercial or military pilot without 20/20 eyesight (allowed to use glasses but up to a certain threshold); reason being able to track small/fast objects at a distance along with clarity reading the instruments/influence of weather patterns/influence of day-night/etc.
    I doubt anyone would say a fighter pilot at high velocity speeds 100-200ft above the ground and sometimes lower has the eyesight of a pensioner, let alone when they do valley training at around/over 450 knots, or deciding whether a target is hostile or not.
     
    #10 CSI PC, Jan 23, 2018
    Last edited: Jan 23, 2018
  11. DmitryKo

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    Medical research papers published in peer-reviewed medical journals tend to assume otherwise.

    I did a search for 'logMAR acuity distribution adults' and 20/20 (logMAR 0.0) is universally accepted as 'normal' across all ages (I can look up non-free articles through ScienceDirect, SpringerLink and Wiley subscription from my university).

    Here is historical medical research data published by US National Center for Health Statistics (NCHS):
    Series 11. Data From the National Health Examination Survey

    No. 201. Monocular Visual Acuity of Persons 4-74 Years: United States, 1971-1972 (1977)
    https://www.cdc.gov/nchs/data/series/sr_11/sr11_201.pdf

    No. 127. Visual Acuity of Youths 12-17 Years: United States (1973)
    https://www.cdc.gov/nchs/data/series/sr_11/sr11_127.pdf

    No. 101. Visual Acuity of Children: United States (1970)
    https://www.cdc.gov/nchs/data/series/sr_11/sr11_101.pdf


    Yes, actually 20/20 is the 'mode', i.e. the value with the highest probability - acuity distribution doesn't really look like normal (Gauss) curve, rather as a Log-normal distribution.

    I can recognize the letters on the 20/15 line on your Snellen chart, and even some letters on the line below if I stare at each letter for a few seconds.

    I don't think I would be able to actually read small text or recognize complex crowded shapes used in other modern visual charts.

    I do not use glasses, but I can notice a degradation of my vision when looking on bright colored objects, such as traffic lights with countdown timers.
     
    #11 DmitryKo, Jan 23, 2018
    Last edited: Jan 23, 2018
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  12. Kyyla

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    I don't know why this is an interesting debate.

    Most young people with no eye pathology can see around 25/20 with proper spectacle correction monocularly. I can do that too. A few lucky ones can do that even without glasses. As people get older, BCVA goes down so in older people I'm not that interested if someone sees "only" 15/20. Often you can not detect anything significantly wrong with their eyes and 15/20 vision is perfectly adequate for everyday tasks.

    So 20/20 is a pretty good cutoff for normal in a large adult population. Like everything in medicine it's a statistical definition and there will be people who have suboptimal vision and vice versa.

    Source: am an ophthalmologist. I'm not gonna go searching for academic articles for textbook/everyday stuff.
     
  13. zed

    zed
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    Mate cheers for that but I see nothing there that disproves what I say, the first link contains the other 3 papers I assume.
    The last 2 papers are about children which we both agree do see better than 20/20. Its the adults we want to know about,
    The 201 paper does have the age range 12-74 where it saiz 74.9% of ppl have 20/20 or better vision, unfortunately it doesnt say how many have 20/15 etc or better
    The 127 paper does mention
    OK but thats still only young adults, we're missing the 25-40, 41-60 etc groups
    The surprsing factor is these values are all unaided (without corrective lens), which to me is shockingly high, perhaps eyesight was better then (less screens?). Now people wear glasses/contacts to improve their vision thus any numbers quoted are going to be a lot higher, eg I'm worse than 20/200 but have 20/15 vision with my glasses on

    I did find a paper that tests old people
    https://pdfs.journals.lww.com/optvi...XURcarTB4nROXc=;hash|sCWtIgoYflX0LkGOG1JhWg==

    though this deals only with people 58 years and older, now the data from this paper suggest 20/19 for those aged 58 then roughly 20/20 until ~65 then it starts to drop off.
    Now I'm not sure if they tested the people with corrective lens if thats what they needed (papers a bit long)

    This would be a decent article for someone to write 'How did the myth of 20/20 being normal or perfect vision originate'
    how did this bugbear of mine start? :grin:
    Retina screen, when apple came out and said it was impossible to see the pixels. I said OK thats cool, until I got an iphone & I looked at the screen (at X distance and said hmm I can see the pixels) and then asked another person and another and another and they all could see the pixels, thats when I knew its prolly marketing BS
     
  14. CSI PC

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  15. zed

    zed
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  16. DmitryKo

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    The viewing distance calculator mentioned in my original post above has a downlodable Excel file version which allows you to change visual acuity - the difference seems to be close to linear though, so 20/15 visual acuity should result in a ~34% increase of the optimal distance (or proportional decrease of diagonal size/pixel pitch).
    http://carltonbale.com/home-theater/home-theater-calculator/

    Anyway, 20/20 has been widely accepted by the medical community as the norm - I believe this originates from initial definition by Dr. Snellen. There are a few dissenting opinions, but until someone proves existing statistics to be seriously biased, it looks like better acuity is mostly encountered in young adults.
     
  17. Shifty Geezer

    Shifty Geezer uber-Troll!
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    Zed manages that a lot. The secret is knowing his own special variation of English - he talks in extremities. For normal people, we'd have a scale from fabulous to terrible. On that scale, 20/20 vision is 'good'. For Zed though, anything less than phenomenal == shit. Ergo, 20/20 vision is 'bad', because he has no gradations between bad and good. If everyone could apply a language filter to Zed's postings, and interpret every 'bad' as 'less than ideal', it'd all make sense. ;)
     
    #17 Shifty Geezer, Jan 25, 2018
    Last edited: Jan 26, 2018
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  18. BRiT

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    So one could say Zed's communications are shit?
     
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  19. Shortbread

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    Depends on your interpretation of sh**, especially with today's youth.

    Dude, that was some good sh**!

    Dude, that sh** was terrible!
     
  20. Silent_Buddha

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    Is this on the Binary Zed scale of Fantastic or Shite? Or is it on the scale that normal people use? :D

    Regards,
    SB
     
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