Monovision vs. Corrective Lens Prescription

Discussion in 'Eye-Care' started by Chris Dobyns, Sep 28, 2004.

  1. Chris Dobyns

    Chris Dobyns Guest

    Have been reading with some interest about this monovision solution to
    wearing reading glasses or bifocals. Generally, I understand how it
    works and how the brain can make one eye compensate for distance and
    still allow close-up detail vision. Was wondering how that the
    solution translates into those corrective power values. Since I wear
    contacts with a -3.25 correction and can see close-up using OTC
    reading glasses with a +1.25 correction, is that average monovision
    eye usually prescribed at a power roughly the difference of those two
    values - or around -2.00? Guess that would give some close-up
    capability and still assist with distance vision. I know that exact
    mix is usually obtained through that lens switching at the optometrist
    (". . .is the image better or worse?"). Anybody willing to weigh in
    on the before/after contacts and reading glasses and then the
    monovision prescription?

    Severn, MD
    Chris Dobyns, Sep 28, 2004
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  2. Chris Dobyns

    LarryDoc Guest

    You pretty much have it. If +1.25 provides the near range of focus
    that suits your needs, then the non-distance dominant eye should be
    "corrected" with -2.00.

    And now the issues. Assuming you have normal binocular stereoscopic
    vision and you can train your brain to give that up:

    1. That +1.25 undercorrection will result in a distance visual acuity of
    around 20/80-20/100. If it's your left eye and you live in a country
    where you sit on the left side of the car driven on the right side of
    the road, the view through your left side view mirror will be blurred
    accordingly. Some USA state find that illegal.

    2. You've lost your ability to accurately determine relative distances
    in a 3-D world.

    If you can live with a +.75 undercorrection, you will be able to
    maintain a reasonable amount of distance vision (20/40-ish) and likely
    retain enough fusion for some stereoscopic vision and some depth
    perception. (Depth perception is a complex system of central vision
    lock, parallax, size, shadow and overlap, therefore the real-life effect
    of the monovision varies according to lens power and system reactivity.)

    Or try multifocal contact lenses! If all you need is a +1.25 add,
    that's a pretty simple fix, even with soft contact lenses.


    Dr. Larry Bickford, O.D.
    Family Practice Eye Health & Vision Care

    The Eyecare Connection
    larrydoc at eye-care-contacts dot com (remove -)
    LarryDoc, Sep 28, 2004
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  3. Chris Dobyns

    Chris Dobyns Guest

    Dr. Larry,

    Thanks so much for the nifty and fast response. Wouldn't have
    realized that all that diopter business was so straight-forward and
    that I was smart enough to figure it out.

    Thanks again,

    Chris Dobyns, Sep 29, 2004
  4. Chris Dobyns

    LarryDoc Guest

    You're welcome!

    Yup. That math we learned in elementary school really comes in handy!

    Math-----it adds up!

    LarryDoc, Sep 29, 2004
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