Special vision test for computer glasses?

Discussion in 'Glasses' started by Sherman, Dec 9, 2006.

  1. Sherman

    Sherman Guest

    I'm going to be getting glasses to use with a new laptop
    computer. I assumed that the correct add would just be a
    function of the working distance form the eye to the
    computer's display.

    But then I saw claims that because of all the little dots,
    the eye focuses differently on a computer screen than it
    would on printed text at the same distance. In fact,
    there's a product designed specifically for determining the
    correct refraction for computer use. It uses a simulated
    computer display to do the eye test. The implication is
    that you would get a different result than using an eye
    chart at the same distance. Here's the link:


    And here's a picture of the testing device:


    Frankly, this looks like pure BS to me. But I've been
    fooled before. What do the experts think?
    Sherman, Dec 9, 2006
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  2. You are right on. It IS pure BS. I've looked at their research and
    THEIR OWN DATA proves they are screwed up; they just don't know how (or
    refuse to) understand it.

    w.stacy, o.d.
    William Stacy, O.D., Dec 10, 2006
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  3. Sherman

    Mark A Guest

    There are two issues:

    1. Is there a difference in the Rx with their method of using a computer
    screen instead of a chart (both at computer distance)?

    2. What is the difference in the lens they sell, compared to other computer

    I don't know anyone who always views the computer screen at the same exact
    distance each time, or views the entire screen at the exact same distance.
    It is hard to believe that their measurement technique with an actual
    computer screen will come up with a different Rx compared to a regular chart
    held at computer distance.

    If the distance alone was a factor, then it could easily be corrected by
    moving further or closer to the screen by a few inches.

    Is there something about the lens that is an improvement over other computer
    lenses. I doubt it, except that most computer lenses are made from a normal
    Rx with distance and reading power without a specific measurement of
    computer distance, and a 'standard" adjustment (instead of a custom
    measurement) is made from the reading power to the computer power to achieve
    the optimal computer power in the upper portion of the lens. For example, I
    believe that Zeiss Gradal RD always assumes that the right power for
    computer distance is .50 subtracted from the reading power.

    So their could be some advantage for taking a custom Rx to the computer
    distance, but I don't think using an actual computer screen helps, and a
    good OD could come up with the exact Rx to make a pair of customized
    computer glasses with any of the name brand lenses like Zeiss Gradal RD.
    Mark A, Dec 10, 2006
  4. Sherman

    Burke Gilman Guest

    Confused here -- "optimal computer power in the upper portion of the
    lens" makes no sense to me, especially with a lens like the Gradal RD,
    which I understand is designed to allow a presbyope the ability view
    with clarity far-intermediate targets at 2 or 3 meters through the
    upper portion of the lens. Near-intermediate viewing (computer screens)
    would be through the middle area of the lens...correct?


    Burke Gilman, Dec 10, 2006
  5. Sherman

    Mark A Guest

    Yes, that is correct. The Zeiss Gradal RD has a wider intermediate area that
    is used for computer distance. As you mentioned, and unlike a normal
    progressive, the upper portion does not have the correct distance power
    (usually 2-3 meters max), so you cannot use them for driving.

    Also, some opticians use regular progressives to make custom computer lenses
    with the upper portion optimized for computer distance, and the lower
    portion for reading, and one cannot even see clearly at 2-3 meters in the
    upper portion of the lens. In theory this gives a larger area for computer
    distance, but is less flexible in seeing beyond that (like being able to see
    someone sitting across the desk from you).

    If you go the custom route, you can do whatever you wish, but as you say the
    Zeiss Gradal RD does allow one to see up to 2-3 meters if you give them a
    normal progressive Rx and they make the standard adjustment.
    Mark A, Dec 10, 2006
  6. Sherman

    Burke Gilman Guest

    Am I correct in my understanding that the Gradal RD always has 0.50 in
    the upper portion of the lens and that the lower areas simply add more
    *diopter* as needed to provide the viewer with clarity at closer
    Burke Gilman, Dec 10, 2006

  7. roughly correct. I think they also have rather wider intermediate and
    near zones than do conventional progressives.

    w.stacy, o.d.
    William Stacy, O.D., Dec 10, 2006
  8. actually, I should add that the .5 in the distance is in addition to any
    distance Rx that has been prescribed.

    w.stacy, o.d.
    William Stacy, O.D., Dec 10, 2006
  9. Sherman

    Burke Gilman Guest

    Interesting that some computer glasses are chosen for viewing the
    screen through top portion of the lens. My purposes for an occupational
    progressive are more conventional, however: I need to see clearly and
    find objects at room distances -- up to 3 meters, no more, but also
    need to read up-close and view computer screens at more than arm's
    length. I do require distance correction also, but that's being
    accomplished with contacts (+1.25) and I intend to keep wearing the
    contacts all the time. Instead of continuing to rely upon an assortment
    of OTC readers for near and intermediate distances, I'm thinking the
    Gradal RD might provide an optimal solution for my sometimes demanding
    "room distance" requirements -- provided I can find a pair. -bg
    Burke Gilman, Dec 10, 2006
  10. Sherman

    Burke Gilman Guest

    Ok, I see. The Gradal RD, for the upper area of the lens, always adds
    +0.50 to whatever the user's distance prescription is and that makes
    the "distance" area of the lens a bit blurry for actual far-distance
    viewing, but possibly tolerable for far-distance viewing over short
    period of time.

    Question: I wear +1.25 contacts for distance viewing and continue to do
    so. On top of the contacts, my prescription calls for a near "add" of
    +2.50 for fine reading and +1.25 for reading a computer screen at arm's
    length. If this prescription is applied to an order for a pair of
    Gradal RD, then what will these lenses actually provide? (I'm thinking
    it would be an actual +0.50 in the upper part of the lens, but can't
    figure what the lower up-close viewing area of the lens would provide
    with the Gradal RD design.) -bg
    Burke Gilman, Dec 10, 2006
  11. Sherman

    Burke Gilman Guest

    Actually my contacts prescription is +1.25 for far-away vision. When
    the +2.50 "add" specified in the prescription for supplemental readers
    is included (when I'm wearing my contacts) the total reading power for
    near vision is +3.75.

    So...what I'm now understanding now is that Gradal RD lenses (ordered
    for use with the contact) would have +0.50 in the upper area and would
    have +2.00 added toward the bottom for a total of +2.50.

    The order to Zeiss then would specify 0.00 as the far-distance viewing
    parameter and +2.50 for up close... correct? Worn over my +1.25
    contacts, the total up-close reading power would then be +3.75, the
    middle intermediate area would provide around +1.75, and the upper
    "distance" area would provide a total of +1.75. (A little much for my
    far-distance needs, but I could tolerate it for a while if I wanted

    Will consider customizing an "RD" lens. But wonder if the Zeiss product
    would work better.
    Burke Gilman, Dec 10, 2006
  12. Sherman

    Burke Gilman Guest

    Oops... I think I read too much into your reply... anyway, yeah, my
    supplemental progressives (RD or whatever) precription assumes "0.00"
    for far away and reads +1.25 for computer screen (intermediate) and
    +2.50 for fine reading (up-close). -bg
    Burke Gilman, Dec 10, 2006
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