over-minused contacts

Discussion in 'Contact Lenses' started by CHip, Oct 20, 2004.

  1. CHip

    CHip Guest

    Lurking in alt.lasik-eyes I read the term "over-minused". The reason
    for it is over my head but sounds like what was done with my contacts.
    One eye sees well for distance but not for reading. The other eye
    sees well for reading but not for distance. My reason for RGP
    contacts is a poor LASIK outcome. I can't see well enough to drive
    after dark unless I'm wearing the contacts. The problem is large
    starbursts emanating from every headlight, reflecting off chrome or
    even off water in the street. The over-minus contact controls the
    starbursts better than the "under-minused" lens. Since I have two
    pairs of contacts I wear the over-minused in each eye. That makes
    driving easier but means I need reading glasses to follow a map.

    I've been told the reason is the lasered area is smaller than the
    nighttime pupil. If that is so, why would contacts help? The pupil
    is the same regardless of which contacts I wear. The contacts are
    11.5mm diameter.
    CHip, Oct 20, 2004
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  2. CHip

    Dom Guest

    Too-strong contacts mean your eyes have to focus a bit more (accommodate) to
    see; accommodation is linked with pupil size (more accommodation = smaller
    pupil size, to give a greater depth of field); therefore the stronger
    contacts give you slightly smaller pupils. Also, the RGP contacts create a
    new optical surface which tends to "iron out" any irregularities in your own
    post-lasik corneas which might be contributing to your problems.

    Dom, Oct 21, 2004
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  3. CHip

    Dr Judy Guest

    "Over minused" means that your glasses or contact lenses have more minus
    power or less plus power than your cycloplegic refraction. A person who is
    over minused may see well at both far and near. It is important in LASIK
    because the surgeon wants to correct the cycloplegic refraction, not the
    habitual overminused refraction

    The situation you describe is called monovision, used for presbyopes wherein
    one eye is given the correct distance correction and the other eye is over
    plussed (less minus, more plus than needed) to allow for reading. I am
    guessing you are over age 40. If both your contacts were set to the correct
    distance refraction, you would need reading glasses over them to read.


    My reason for RGP
    Likely neither lens is over minus. I'm guessing that after LASIK you were
    left with mild myopia, ie the surgery did not fully correct your myopia.
    During the day, when your pupil is small, depth of focus effects make your
    vision acceptable without glasses. At night, when the pupil is larger you
    lose your depth of focus and then need your myopia correction. Uncorrected
    myopia will cause starbursts etc.

    That makes
    As stated earlier, if over age 40, you will need reading glasses when your
    distance vision is fully corrected.
    The unlasered area still has your original myopic refractive error and the
    contacts contain myopia correction.

    Dr Judy
    Dr Judy, Oct 21, 2004
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