Heat cleaning soft disposable lens

Discussion in 'Optometry Archives' started by George Bray, Mar 19, 2005.

  1. George Bray

    George Bray Guest

    I've read that many/most modern soft lens should not be placed in a
    heat sterilisation unit, presumably because 100C will damage the
    structure of the lens.

    I placed an 'old' Acuvue Advance (2 week disposable, silicone hydrogel
    based) lens in all-in-one solution within a contact lens case, and
    then placed that in a saucepan of tap water heated to 60C. My
    objective was to remove lipids and other deposits clouding the lens.
    Daily cleaner, ultrasonic treatment and rubbing had failed to get the
    lens clean enough. It worked, at least when holding the lens up to the
    light afterwards. The lens looks much cleaner. I have not worn it
    again yet. Any reason why I should not? The lens had been worn for
    only one week (day time use only) prior to the heat treatment.

    Do you think 60C is hot enough to remove lipids and other deposits?
    Next time, I may try 40C in saline solution What do you think would be
    the optimal temperature in order to help clean the lens but not damage
    it? I assume nearly all the lipids and deposits come from my eyes, so
    they must have a fairly low melting point.

    I am not interested in sterilisation here. That will be done by a 8
    hour soak in hydrogen peroxide as a subsequent step.

    Regards
    George
     
    George Bray, Mar 19, 2005
    #1
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  2. George Bray

    Dr Judy Guest

    The only thing that heat does is disinfection. It does not assist in
    cleaning lenses, actually the opposite: heat tends to denature protein and
    make it more adherent to the lens and it "bakes" other deposits on. To
    clean, use a soft lens cleaner. Your fitter can recommend one.

    Some people's tears do not get along with silicon hydrogel lenses. If you
    are getting rapid deposit build up, your fitter will likely suggest a
    different lens.

    Dr Judy
     
    Dr Judy, Mar 19, 2005
    #2
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  3. George Bray

    George Bray Guest

    Thank you for your helpful response. It leads to another concern of
    mine: whilst my optician can actually inspect my eyes, how can the
    optician be any better placed to advise on such matters than people at
    this forum? Perhaps you just happened to come across the subject of
    lens heating at a conference. My optican might not have a clue.
    Several heads are better than one. The predictable response of my
    optican to heating a lens will be 'don't do it'. If the optician, or
    I, contact the lens manufacturer, of course, they will say ' don't do
    it'. I suspect it will be more out of ignorance and 'covering
    themselves' than any confident knowledge of test results and firm
    evidence.

    If denatured protein and/or baked deposits are now present within my
    lens, would you expect that I should be able to see the effects with a
    microscope, if not with my own eyes, when the lens is held up to a
    light (not worn).

    How is it that heat sterilisation was used on non-disposable soft lens
    - much hotter than I used - without adverse affects from baked
    deposits and protein?

    Regards
    George
     
    George Bray, Mar 20, 2005
    #3
  4. George Bray

    Dr Judy Guest

    Disinfection, cleaning and care of contact lens is a routine part of the
    basic trraining of contact lens fitters, not something they may or may not
    have come across at a conference. A fitter is expected to know the
    different materials, the correct methods of care and the methods that will
    damage the lens. Heat is unsuitable for some lenses, alcohol is unsuitable
    for others, certain preservatives are not compatible with still others.
    Manufacturers must test their lenses with the various care systems and will
    recommend or warn against some systems based on the results of testing.

    Heating of materials is done by both manufacturers and other researchers.
    For most of the higher water materials, heat causes irreversible parameter
    changes in the lenses. This is not just a "guess", it is a measured, tested
    and known fact.
    You would need magnification (>20X), and retroillumination to see visable
    deposits. Deposits bound to the lens require cutting up the lens and
    testing with reagents to discover what is bound. This type of testing of
    worn contact lenses has been done extensively by researchers and results
    have been published.
    It did have adverse effects, quite nasty ones. I well remember all the
    yellowed, distorted soft lenses that resulted from heat disinfecton. Before
    disposables I saw several patients every week with Giant Pappillary
    Conjunctivitis (inflammation of eye lid lining) and several cases montlhy of
    corneal inflammation, both due to denatured protein on the lens.

    In the bad old days, heat disinfection was used in combination with daily
    cleaners, weekly enzymes, in office ultrasound etc etc etc to deal with
    deposits with limited success and at great nuisance and expense to the
    patient. Despite all that cleaning, non disposable lenses will have a
    bound biofilm after 60 to 90 days of wear. The difficulty of keeping soft
    lenses clean was motivation for the development of disposable lenses.
    Instead of the patient spending $200/year on lens cleaning supplies and
    $100/ year on lenses, we switched to having them spend $200 to $250/ yr on
    lenses and $60 on multipurpose lens care.

    If you are depositing lenses after one week wear, you need a daily
    disposable or a less deposit prone biweekly. Or you need to address any
    systemic problems like allergies, acne rosacae, blepharitis that cause you
    to have so much protein, lipids etc in your tears.

    See your fitter.

    Dr Judy
     
    Dr Judy, Mar 20, 2005
    #4
  5. George Bray

    George Bray Guest

    Your explanation (much longer than the short extract above) is
    excellent and convincing. Thank you very much for your advice.

    Regards
    George
     
    George Bray, Mar 21, 2005
    #5
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