Diopters to 20/something conversion. The math and science behind this!

Discussion in 'Optometry Archives' started by acemanvx, Jan 10, 2006.

  1. acemanvx

    acemanvx Guest

    Hello everyone, post your dioptric pescription(how bad are your eyes),
    your UCVA(uncorrected) and BSCVA(corrected by glasses) Also if you know
    anyone's vision, post that too. I have done much research on the
    correlation of diopters and 20/xxx and have compiled several charts,
    formulae, tables and comments on the results obtained thus far. To test
    for this, do it in room light or dim light. Make sure the eyechart is
    well illuminated and your not squinting at all or recalling from memory
    or guessing. Blur preception is of course allowed.

    I and most optometrists have found that -.25 diopters doesnt cost you a
    single line but makes the existing line blurry but still readable. Some
    say it costs half a line. Such as if you can see half of 20/15 with a
    -.25 lens, youll be a full 20/20 but wont be able to see better than
    that uncorrected. Another example is if your seeing all of 20/20, you
    may miss half of the 20/20 with -.25 diopters. Others have said it
    didnt affect their ability to read a line, just made it harder to do
    so.

    Minus half diopter(-.5) is generally accepted as resulting in one full
    line loss. This means 20/15 becomes 20/20 and 20/20 becomes 20/25. If
    you can see half of 20/15 youll be seeing half of 20/20.

    Minus one diopter(-1) generally gives you half visual accuracy. My
    friends who see 20/20 with glasses see 20/40 without their -1 glasses.
    Ditto for 20/15 with -1, 20/30 uncorrected. I was 20/50 corrected to
    20/25 with a -1 lens years ago.

    Higher dioptric values become harder to calculate and predict,
    especially when you get to -6 and up. Someone could be -4.5 another
    -5.25 and both see 20/400 UCVA. The -5.25 probably will see a much
    blurrier 20/400 than the -4.5 but generally, 20/400 represents a
    moderate of myopia around -5 diopters. One website said the range was
    -4 to -6 for 20/400 and your best corrected vision played a big factor.
    Someone whos 20/15 corrected needs more diopters to see the same blur
    as another with 20/30 corrected. For me, my left eye at -5 or so
    couldnt see 20/400 while my right eye at -4.5 or so just barely, barely
    saw 20/400. I know two people who passed V3 requirement which states
    you have to be 20/400 or better uncorrected and both were barely 20/400
    with -5.5 pescriptions with 20/15 corrected. Those two guys said they
    dont know anyone else -5.5 or more who passed V3 which requires 20/400.
    They probably didnt have the great 20/15 corrected vision with glasses
    so for them, -5 was the limit(20/20 corrected) I am not correctable to
    20/20 so my limit is even less.

    Few eyecharts go beyond 20/400 so info is scarce past this. I have a
    solid grasp on dioptric values below -6(mild to moderate myopia), but
    for -6 and up which is high myopia I am less certain how this converts
    to diopters. I do know high myopes are worse than 20/400 but how bad
    exactly? Also theres much fewer high myopes than low and moderate
    myopes so much of my info is on low(er) myopes and their diopters to
    snellen accuracy.

    One could stand closer but then accomodation needs to be taken into
    account. I can see the 20/200 E from 10 feet less blurry than the
    20/400 E from 20 feet. At 5 feet I see the 20/70 line but im certainly
    worse than 20/280. I experienced .67 diopter accomodation from the 5
    feet mark.

    If any of you have charts and formulae, on what expotentional scale
    does this equal to? I know that going from -1 to -2 is only twice as
    bad(20/40 and 20/80), but going from -3 to -6 is definately more than
    twice as bad(20/150 and 20/500?), blurs much more than twice. Does this
    gap become even larger still at -6 to -12(20/500? and 20/????) where
    the number of times more blurry increases expotentionally?

    Me and many others are curious about this and this topic has been
    posted before many years ago. Its also useful for some occupations such
    as pilot, soldier, law enforcement, etc where they have a requirement
    for both corrected(BCVA) and uncorrected(UCVA) vision and people ask
    all the time if their UCVA is good enough to make the cut.
     
    acemanvx, Jan 10, 2006
    #1
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  2. acemanvx

    acemanvx Guest

    ive edited and deleted trying to make the paragraphs show correctly.
    Let me retry


    Hello everyone, post your dioptric pescription(how bad are your eyes),
    your UCVA(uncorrected) and BSCVA(corrected by glasses) Also if you know
    anyone's vision, post that too. I have done much research on the
    correlation of diopters and 20/xxx and have compiled several charts,
    formulae, tables and comments on the results obtained thus far. To test
    for this, do it in room light or dim light. Make sure the eyechart is
    well illuminated and your not squinting at all or recalling from memory
    or guessing. Blur preception is of course allowed.

    I and most optometrists have found that -.25 diopters doesnt cost you a
    single line but makes the existing line blurry but still readable. Some
    say it costs half a line. Such as if you can see half of 20/15 with a
    -.25 lens, youll be a full 20/20 but wont be able to see better than
    that uncorrected. Another example is if your seeing all of 20/20, you
    may miss half of the 20/20 with -.25 diopters. Others have said it
    didnt affect their ability to read a line, just made it harder to do
    so.

    Minus half diopter(-.5) is generally accepted as resulting in one full
    line loss. This means 20/15 becomes 20/20 and 20/20 becomes 20/25. If
    you can see half of 20/15 youll be seeing half of 20/20.

    Minus one diopter(-1) generally gives you half visual accuracy. My
    friends who see 20/20 with glasses see 20/40 without their -1 glasses.
    Ditto for 20/15 with -1, 20/30 uncorrected. I was 20/50 corrected to
    20/25 with a -1 lens years ago.

    Higher dioptric values become harder to calculate and predict,
    especially when you get to -6 and up. Someone could be -4.5 another
    -5.25 and both see 20/400 UCVA. The -5.25 probably will see a much
    blurrier 20/400 than the -4.5 but generally, 20/400 represents a
    moderate of myopia around -5 diopters. One website said the range was
    -4 to -6 for 20/400 and your best corrected vision played a big factor.
    Someone whos 20/15 corrected needs more diopters to see the same blur
    as another with 20/30 corrected. For me, my left eye at -5 or so
    couldnt see 20/400 while my right eye at -4.5 or so just barely, barely
    saw 20/400. I know two people who passed V3 requirement which states
    you have to be 20/400 or better uncorrected and both were barely 20/400
    with -5.5 pescriptions with 20/15 corrected. Those two guys said they
    dont know anyone else -5.5 or more who passed V3 which requires 20/400.
    They probably didnt have the great 20/15 corrected vision with glasses
    so for them, -5 was the limit(20/20 corrected) I am not correctable to
    20/20 so my limit is even less.

    Few eyecharts go beyond 20/400 so info is scarce past this. I have a
    solid grasp on dioptric values below -6(mild to moderate myopia), but
    for -6 and up which is high myopia I am less certain how this converts
    to diopters. I do know high myopes are worse than 20/400 but how bad
    exactly? Also theres much fewer high myopes than low and moderate
    myopes so much of my info is on low(er) myopes and their diopters to
    snellen accuracy.

    One could stand closer but then accomodation needs to be taken into
    account. I can see the 20/200 E from 10 feet less blurry than the
    20/400 E from 20 feet. At 5 feet I see the 20/70 line but im certainly
    worse than 20/280. I experienced .67 diopter accomodation from the 5
    feet mark.

    If any of you have charts and formulae, on what expotentional scale
    does this equal to? I know that going from -1 to -2 is only twice as
    bad(20/40 and 20/80), but going from -3 to -6 is definately more than
    twice as bad(20/150 and 20/500?), blurs much more than twice. Does this
    gap become even larger still at -6 to -12(20/500? and 20/????) where
    the number of times more blurry increases expotentionally?

    Me and many others are curious about this and this topic has been
    posted before many years ago. Its also useful for some occupations such
    as pilot, soldier, law enforcement, etc where they have a requirement
    for both corrected(BCVA) and uncorrected(UCVA) vision and people ask
    all the time if their UCVA is good enough to make the cut.
     
    acemanvx, Jan 10, 2006
    #2
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  3. acemanvx

    otisbrown Guest

    Dear Aceman,

    Subject: Establishing a relationship between eye-chart and trial-lens

    To do what you request, you just need the tools to do it.

    (Assume that a MEDICAL exam has been made -- and there
    are no MEDICAL problmems -- like glaucoma, etc. All
    ODs are required to check for these conditions, and
    report them to you. There is GREAT VALUE in this
    part of the exam. I always INSIST that the person
    go through this process BEFORE the begin
    working on true-prevention with the plus.)

    In a well lighted room, have the person look at the eye chart.

    Let us say he reads 20/60. You then start placing
    stronger minus lenses in front of his face until
    one lens "clears" the 20/20 line. That is
    how you measure the refractive state
    of the natural eye.

    Do this systeematically, under "room" illumiantion
    and you can establish this relationship or "curve" very
    quickly.

    Was that you question?

    Best,

    Otis
     
    otisbrown, Jan 10, 2006
    #3
  4. THAT IS *NOT* HOW IT IS DONE, AND WILL NOT WORK EXCEPT FOR SOME MYOPES
    WITH NO ASTIGMATISM.

    Re the conversion idea, I suggest ace go into deja news and research
    "The Dead Horse" equation I and others developed several years ago on
    this news group. Been there, done that.

    w.stacy, o.d.
     
    William Stacy, Jan 10, 2006
    #4
  5. acemanvx

    A Lieberman Guest

    Dear Ace,

    Please disregard Otis's postings. He is not in the medical profession and
    not in the position to give medical advice.

    Sure looks like medical advice above.....

    Allen
     
    A Lieberman, Jan 10, 2006
    #5
  6. acemanvx

    otisbrown Guest

    Dear Allen,

    Subject: The difference between measureing the refractive
    state of the natural eye -- and calling a measurement
    a "medical problem".

    The objective measurements could be made by ANYONE with
    some traning an experience.

    Assuming the retina is inherently capable of 20/20 (not
    amblyopic), then let us talk about measureing a
    POSITIVE refractive state for the natural eye.

    In this case, you have the person read the Snellen (in room
    illumination) and he reads 20/20.

    His refractive state might be zero -- or some positive value.

    What you do then, is to take your tria-frame, and using
    your trial-lens kit, you place increasintly stronger PLUS lenses
    in front of his eyes, until you find a lens-strength that "just blurrs"
    the 20/20 line.

    This is a measure of a positive refractive state for the young eye.

    In NONE of these measurements have I suggested "medicine"
    or anything like that. These are simple objective measurements --
    i.e.,
    science -- not medicine.

    If I said that I was going to write a "prescription" then everything
    would "change".

    BUT I NEVER SAID THAT!

    Get it? Yet?

    Otis
     
    otisbrown, Jan 11, 2006
    #6
  7. And then he goes on to describe a SUBJECTIVE method of measuring
    hyperopia (a very primitive, and certainly NOT an *objective* method).
    Any body who doesn't know the difference between objective refraction
    and subjective refraction should NOT be telling ANYONE how to "do it".

    Speaking of subjective and objective evaluations, I recommend the
    recliner for otis, handcuffs for dick, and a straight jacket for ace.

    Why do old reruns of the 3 stooges keep popping up in my mind???

    w.stacy, o.d.
     
    William Stacy, Jan 11, 2006
    #7
  8. acemanvx

    otisbrown Guest

    Dear Mike,

    There you go again, converting refarctive-state measurements
    into "medicine" which they are manifestly NOT.

    Otis
     
    otisbrown, Jan 11, 2006
    #8
  9. acemanvx

    acemanvx Guest

    Lets not argue about other topics in this thread. I will go back on
    topic and talk about diopters to 20/xxx correlation. So guys, post your
    pescription, UCVA and BCVA and the results of anyone you know for us to
    learn
     
    acemanvx, Jan 11, 2006
    #9
  10. acemanvx

    otisbrown Guest

    Dear Wiliam,

    If I paid $ 100 k for college, and
    120 K for OD school, I guess
    I would be stuck on my
    God-hood.

    Ace is asking straight questions.

    Why not attempt to give him
    straight answers -- rahter
    than insulting him.

    Ace is learning a great deal -- about
    you arrogance in this discussion.

    It that profesional?

    What does Ace-Man think
    of your response -- I wonder.

    Otis
     
    otisbrown, Jan 11, 2006
    #10
  11. acemanvx

    Neil Brooks Guest

    Who gives a shit -- I wonder.
     
    Neil Brooks, Jan 11, 2006
    #11
  12. acemanvx

    Chris

    Joined:
    May 2, 2016
    Messages:
    2
    Likes Received:
    0
    -0.00, 20/15
    -0.25, 20/15
    -0.50, 20/20
    -0.75, 20/25
    -1.00, 20/30
    -1.25, 20/30
    -1.50, 20/40
    -1.75, 20/40
    -2.00, 20/50

    These are for mild myopia. Moderate myopia will come soon.
     
    Chris, May 2, 2016
    #12
  13. acemanvx

    Chris

    Joined:
    May 2, 2016
    Messages:
    2
    Likes Received:
    0
    And what is your accuracy of your estimate?
     
    Chris, May 9, 2016
    #13
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