First extended wear - is this usual?

Discussion in 'Optometry Archives' started by Darren Smith, Oct 15, 2004.

  1. Darren Smith

    Darren Smith Guest

    Worn lenses for 10 years+ and inititiall had issues with red eye caused by
    wearing lenses during all waking hours. A change to Proclear a couple of
    years ago seemed to overcome any issues (as I were told then they are the
    most oxygen permable lens?)

    During the last check up the optician noted that the proclear was moving a
    lot but if it doesnt bother you it isnt a problem. I then mentioned about
    extended wear and the Ciba lens was produced to try.

    I did not realise previously that the proclear only comes in one size
    (14.2/8.6) however the optician fitted a 13.8/8.4 in the Ciba lens. I have
    read the ciba site that suggests that a 8.6 be fitted first and taken to 8.4
    in the event of a poor fit. Is this normal or should I have been given a 8.6
    lens instead? (having said that I have had 8.4 lenses before in
    Surevue/Acuvue)

    Upon fitting the new lenses were not noticible and (to me) seem to better
    fit. If I slide the lens of the cornea (1/2 way) it will slide back into
    place. The lens is more relucant to slide upwards as it is less flexible
    than the old proclear and centers better. There is some small movement on
    the lens that can be detected when blinking at night (as has always been the
    case with contact lenes)

    This morning it felt strange to wake up with vision. After all these years I
    was told higher water content is better, and it was not allowed to sleep
    even one night - now suddenly I am told that a 24% water contact lens is
    good and you can sleep in it. Very strange!. The lenses were still in the
    same state as the night before, if I had slept in the proclear they would
    dry out and become imobile (i.e drops before to get them out). The right
    lens was perfect, however the left lens felt slightly "dry" and less mobile.
    A couple of drops in the eye and all seems fine again? Is this normal
    experience?

    The other thing I have noticed is that I have been precribed a higher power
    lens for the Ciba compared to Proclear. With proclear I had a -5.75/-5.50
    but with the ciba I have been given 2 -6.00. I did query this and was told
    it was because of the design? Do ciba have a different method of calculating
    power to everyone else?

    Any comments or advice appreciated (as I havent got an appointment) again
    untill next week.
     
    Darren Smith, Oct 15, 2004
    #1
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  2. Darren Smith

    LarryDoc Guest

    A few years ago that was true. It is no longer.

    [snip]
    Different lens materials and designs fit differently, so suggested
    curves and diameters are only guidelines for starting points in the
    fitting process. On eye observation is how we fit lenses.

    [snip]
    With the new silicone-based lenses, the old "more water is better = more
    oxygen" is no longer applicable.
    See comment above about fitting.
    Enjoy your new lenses and remember to follow the practitioner's
    recommendations. If you experience anything unusual, call him/her.

    -LB

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

    The Eyecare Connection
    http://www.eyecarecontacts.com
    larrydoc at eye-care-contacts dot com (remove -)
     
    LarryDoc, Oct 15, 2004
    #2
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  3. Darren Smith

    Dr. Leukoma Guest

    Proclears were, and still are a technological advancement. The material is
    derived from phosphorylcholine, or PC. The PC technology has been widely
    applied in a number of implanted medical devices and blood tubing to
    prevent clotting. In the contact lens, it helps prevent deposits and also
    binds more molecules of water to the surface, making it extremely wettable.
    Proclears tend to move more.
    Proclear Compatibles come in 8.2 as well as 8.6 base curves. If you ask
    Ciba, they will tell you that the 8.4 base curve is used the most. I use
    it the most. The same base curve will behave differently depending upon
    lens diameter and lens material.
    With old hydrogel technology, oxygen transmission was based upon water
    content. Unfortunately, there were limits. With silicone hydrogels, the
    oxygen permeability is directly related to the percentage of silicone, and
    inversely related to the percentage of water. A lens of 100% silicone will
    have greater oxygen permeability than one with 50% silicone, and a silicone
    hydrogel with 24% water will outperform any hydrogel.
    Your prescription may have changed. But, the steeper lens may be creating
    a plus tear lens that needs to be offset with more minus in the lens power.
    I'll send you the bill.

    DrG
     
    Dr. Leukoma, Oct 16, 2004
    #3
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