RGP lens material choice

Discussion in 'Optometry Archives' started by obsrving, Feb 3, 2008.

  1. obsrving

    obsrving Guest

    If you were to choose an (r)GP lens material today, which would be
    first on your list?

    Assumptions: Normal tears, slight propensity for dry (computer) eye,
    and no history of o2 depravation due to soft contacts. Slight
    astigmatism and low (-2.5) prescription. Eyes are otherwise within
    normal shape and consistency. Desire for clearer vision than soft
    contacts can provide, comfort level has not been an issue in the
    past. Cost (within reason) is not a consideration. Lasik is not an
    option for personal reasons, but tests show that "it would be a slam
    dunk" and that the corneal thickness is "very good".

    Overnight wear would be preferred, but not required. (3-5nights max)



    The two materials that pop up most often in web and usenet searches
    are the Boston XO2 and the Menicon Z materials.

    Advantage to xo2 seems to be a slightly stiffer lens (hard to put into
    a true comparison with the MZ lens though) with similar dk and what
    they consider to be a better/easier wetting capacity without plasma
    treatment.

    Disadvantages to xo2 appear to be short time active in the USA and
    daily wear only. I am assuming the daily wear status is solely due to
    FDA paperwork and studies required for overnight wear, but suffice it
    to say that it cannot be currently prescribed in that manner.

    Advantages to the MZ (or MZa) lens material appears to be that it is
    very thin, excellent wettability (via plasma treatment), extended wear
    compatible and has been on the doctors shelves for years so plenty of
    experience with fitting and use. Easy to replace due to wide
    availability in the USA.

    Disadvantages to the MZ material appears to be shorter lifespan due to
    plasma treatment, "older" material (though that might not actually be
    a disadvantage), possibly less wettable.

    Other materials that pop up are the Hydro 2 for a very low wetting
    angle and the Boston ES for ubiquity.
     
    obsrving, Feb 3, 2008
    #1
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  2. obsrving

    Don Guest

    I strongly recommend the Menicon Z lenses. I wore the same pair
    of Boston Equalens RGP contacts for over 10 years on an extended wear
    basis (removed one night per week). They were approved for extended
    wear back then, but were since change to daily wear and I never
    learned about that (not that it would have mattered since I had no
    problems).
    When I needed trifocal multifocal lenses at age 54, I
    investigated my options like you have, and was strongly sold by the
    huge DK of Menicon Z lenses. I have had them for 5 months now and
    wear them continuously except for one night per week. They are
    FANTASTIC! I LOVE them! My eyes feel better in the morning than at
    night. According to one study I found, the oxygen transmissibility of
    Menicon Z lenses is higher that what the eye experiences at night with
    the eyelids closed. Humans actually have slight corneal edema in the
    morning from oxygen deprivation from having their eyes closed all
    night. Well, Menicon Z has higher DK than that. I have zero
    spectacle blur when I take my contacts out. My glasses prescription
    is crystal clear.
    Another study I found was interesting. FDA data shows that
    extended wear rigid lenses are slightly safer than extended wear
    soft. I think this is because their smooth surfaces make them easier
    to clean well, unlike soft lenses that are somewhat sponge-like.
    Anybody that can learn to tolerate Rigid GPs should use them over Soft
    GPs for this reason alone. They are also much cheaper because the
    rigid lens lasts forever. My experience has been that optometrists
    shy away from Rigid lenses for this reason. They make less money.
    I wanted to try multifocal lenses to get away from wearing
    bifocals over my contacts. My optometrist first tried a concentric
    ring design, but with the bifocal curve on the back surface of the
    lens. This created spectacle blur such that my glasses were not in
    prescription for about two days due to a temporarily deformed cornea.
    Next he tried weighted lenses (just like trifocal glasses) but they
    were not satisfying. Rapid eye movement, while changing lanes for
    example, caused the bifocal lens to create blurred vision until they
    settled down. We then tried the Menifocal Z concentric ring design
    with the bifocal curve on the front surface. They are a MIRACLE! The
    lenses magically adjust to near, intermediate (computer), or far
    without me giving it a thought. For anyone thinking about trifocal
    contacts, I recommend trying these.
     
    Don, Feb 5, 2008
    #2
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