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Thread: Contact Lens Education

  1. #51
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    RGP Lenses

    RGP Lenses and occasionally PMMA lenses will develop a layer of deposits, that with time will build up a even with a concientious patient useing the best of care and cleaning. Usually this can be seen with either a little magnifcation or staining of a lens viewed dry. In some cases they deposits seem to be uniform and transpearent and are only evident when you see layers being removed by polishing. I suspect this is why some practioners (along with a desire to kick sales along) feel that HGP's loose permeability. The cure: cleaning and polishing the lens, yes you can charge for this and it's all profit without a wholesale bill. The patient's will love you.

    But the fine line is: Don't polish lenses that do not need it. Every polishing slightly (sometimes more than) distorts the lens no matter how expertly done. You will abberate the lens slowly or rapidly, so the less unnecessiary polishing, the better.

    Chip.

  2. #52
    Master OptiBoarder Joann Raytar's Avatar
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    Chip:

    I have been told certain all-in-one solutions won't cause as much bleaching of colored contacts as other solutions will. Is this truthful or just a sales pitch?

    What solution do you tend to recommend most to new soft contact lens wearers?

  3. #53
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    Don't know

    Jo:

    I don't know. I do know that certian manufacturers recommend that some soft lenses not be used with certian care regimens. And do know that most colored lenses will fade. Do not think that this is due to peroxide systems, though. Suspect that most of the claims for most one~step sollutions are sales propaganda.

    Have you noticed that Trans~air brown turns to Trans~air gray after a year?

    I also know that if the solutions for all rigid lenses were separate wetting and soaking the lenses would not have most of the "deposits" they have.

    Chip

  4. #54
    Master OptiBoarder Joann Raytar's Avatar
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    Thanks Chip! I agree with you:
    I also know that if the solutions for all rigid lenses were separate wetting and soaking the lenses would not have most of the "deposits" they have.

  5. #55
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    An old pearl.

    Many years ago an employer of mine who had a frustrating day as a hard contact lens fitting consultant came in and exclaimed: "Why can't they just get the concept that a lens is either too damn flat or too damn big?"

    Jim Diprey

    In this I think he conveyed more fitting knowledge than most of the industry has.

    Chip

  6. #56
    Bad address email on file Tim Hunter's Avatar
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    chip anderson said:
    The patient rub the lens manually with the thumb and forefinger for one full minute with wetting solution or conditioning solution as the advertising men may refer to it. Rinse the lens by dipping it in a glass of water.
    Chip interesting postings, I've only just found them.

    I'd just warn any UK students that the above statements and the suggestions regarding checking RGPs might cause them a problem in a UK exam.

    You may not know that we have this lovely thing called new variant CJD or vCJD over in the UK (cows eat sheep with scrape, people eat cows with BSE, people get vCJD, possibly!). The Government here in its infinite wisdom has suggested that following a report from SEAC (advisory board on BSE/vCJD)there is a theoretical and unproven risk of transfer of the prion infective agent on trial contact lenses. So most practitioners in this country have gone to single use trial lenses or empirical ordering. To cut to the chase checking the RGP contact lenses could potentially contaminate them (especially if you've not sterilised your equipment with 2% sodium hypochlorite for at least one hour), as they are delivered sterile by the lab and whilst I wouldn't get too worked up about it, some examiners might.

    T'other thing is we have this little bug called acanthoemeba which lives in tap water, slight risk of contamination even with RGP lenses, so we wouldn't recommend use of tap water at any point in the cleaning process unless it has been boiled and allowed to cool first.

    Personally I advise against cleaning with thumb and forefinger and prefer resting the lens anterior surface down in the palm of your hand and cleaning with your little finger as I think this places less stree on the lens, but that's a personal opinion.

  7. #57
    Bad address email on file Tim Hunter's Avatar
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    Tim Hunter said:
    Personally I advise against cleaning with thumb and forefinger and prefer resting the lens anterior surface down in the palm of your hand and cleaning with your little finger as I think this places less stree on the lens, but that's a personal opinion.
    :hammer:


    Should have read ...places less stress..."
    Excellent I'm failing the spelling bee and quoting my own words to correct them, I obviously need the next four days off, oh I have them!!
    :D

  8. #58
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    Tim:

    We have a few problems with our government thinking it has infinite wisdom too. Don't think Acanthomeba is as much a problmem on rigid lenses and/or tap water as your government does. However I do remember Joe Soper buying five gallon jugs of distilled water, having them taken to Baylor and tested, results: 3 of 5 had acanthomeba. Also don't think Acanthomeba would be a problem if lens properly cleaned and cleared of all mostiure before delivery (but then I don't have a medical lab to research this). But in 40+ years of CL practice I have never had a patient with acanthomeba infection, I think this is because I raise hell about wetting lenses in the mouth, have patients scrub the case out weekly with Johnson's Baby Shampoo, wash hands before handling, etc.

    I also think that the 20-25% of RGP lenses that we receive off base or power or whatever specification is a more frequent risk(if not greater) than possible contamination from our office inpection. Of course, if you government thinks it has infinite wisdom, they probably thind all labs have infinite accuracy and all lenses are accurate.

    Chip

    P.S. What do you think the patients are REALLY going to rinse them with anyway? I am trying to get them away from the sink (as a source of scratches) which to me is the # 1 problem with rigid lenses.

  9. #59
    Bad address email on file Tim Hunter's Avatar
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    Chip

    agree it's unlikely all your patients will be scrupulous about not using tap water, but I give em my it's a small risk but you've only got one pair of eyes and they can at least make an informed decision.

    Much easier for me because I'm based in a hospital and patients tend to be much better behaved in terms of solution compliance.

  10. #60
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    Tim:

    Also concider that every patient is going to shower with tap water every day. Many times a week tap water will enter the eye. To my knowledge, no one in the U.S. has ever gotten acanthomeba from this. I think we are just being over protective.

    Kind of like when Phyllis Rakow wrote that that patient should wash thier hands with anti-bacterial soap. I wrote back to her that germ counts were the same whether the patient used plain soap or anti-bacterial soap. Her answer: " People expect to see an anti-bacterial soap in a doctor's office."

    My opinion, chemicals in anti-bacterial soaps might slowly contaminate soft contacts and sting while the lens is being worn. I recommed Ivory Soap in a bar (contains only soap).

    I do think a certian amout of hygiene in the office and think the patients as a rule will be less concientious than we tell them to. But I don't think the patient should act like they need to prepare for scrub surgery before puttin a contact lens on.

    Chip

  11. #61
    Master OptiBoarder Joann Raytar's Avatar
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    chip anderson said:
    Also concider that every patient is going to shower with tap water every day. Many times a week tap water will enter the eye. To my knowledge, no one in the U.S. has ever gotten acanthomeba from this.
    How resilliant do you figure acanthomeba is? I know out here they treat the tap water with so much chlorine you can smell it, especially when the seasons change, I would think that nothing could live in that.

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    Idea Contacheck

    Greetings from the Lonestar state -- land of warped contacts! I appreciate all of your comments on warpage. I am interested in obtaining a Contacheck. I have heard of people using a keratometer to measure base curves -- I never actually knew how it was done. So thank you for the enlightment. Since W/J doesn't exist anymore, does someone still manufacuter the Contacheck? Or should I look on Ebay? I am new out of optometry school and I don't have a lot of extra money -- or I would just buy a radiuscope. I think that maybe a Contacheck would do the trick in the mean time. I appreciate any comments!

    Yours,
    Derek Hamilton
    Austin, Texas

    Quote Originally Posted by chip anderson View Post
    In the summer months we receive more warped and flattened, or even occasionally steepened (rigid) lenses than any other time of the year. Why: Because the UPS trucks are hotter and the labs are more pressed to turn lenses out in a hurry. It is our DUTY to catch these things before they make it to the patient. How are they detected? Method #1 With a radiuscope, If you get a toric pattern or any reading you don't expect, it's wrong. Method #2
    This can be detected with a keratometer and a devise called a contacheck (W/J). Here you supend the lens in water and focus the kerotometer thorugh a 45 degree mirror. How much is too much? 1/4 diopter.

    Chip:drop:

  13. #63
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    Acanamoeba is a spore forming micro-organism that apparently has an affinity for soft contact lenses, but has caused keratitus in rigid lens wearers as well. In its spore form, the organism is extremely hardy, and can withstand boiling water for HOURS. It can also, if memory serves, survive a 3% H2O2 immersion for as long as 24 hours.
    Most keratometers, at least the one's I have seen, include a small plate and lens holder to measure BCs and warpage. It is on a vertical plane, but fulfills the primary requirment that the surface not being measured is fluid- neutralized. There are compensating charts available since the measurement of plus and minus surfaces are different. Derek, if you are planning on purchasing an autorefractor anyway, see if you can obtain one that includes a contact lens function as well, then you may have no need for a radiuscope, at least for a while. If not, the contacheck or similar device should suffice.

  14. #64
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    Dave -- you made my day. I have a Canon autorefractor/keratometer. At your advice, I pulled out the owner's manuel and discovered that, with an attachment, it will measure CL base curves. I am really pleased about that because I would like to use more RGP's in my practice. And of course, I have to be able to read base curves. So -- thank you again.

    Derek

  15. #65
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    Derek, glad to hear you have the auto CL function on your auto refractor. If you have the same unit I have, you should also have the peripheral K function with eccentricity values graphed out. It is essentially a numeric topographer, and can be used for otho-K if such fitting interests you, and can also be used to graph cones, although a full colour topographer is more state-of-the-art for both functions. Good luck on your new practice.

  16. #66
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    Quote Originally Posted by chip anderson View Post
    Finally getting back to this thread.

    Methods of detecting corneal edema.
    1) Observation in slit-lamp best seen with retro (light bounced off iris) illumination.
    2) Central clearance (or sometimes more obscure areas) deminished under flourcein.
    3) Changes in "K" readings from origional pre-fit condition.
    4) Patient symtoms:
    1)Spectacles seem fuzzy on removal of contacts.
    2) Photophobia (sunlight sensitivity) should not be persent in a "perfect fit" of any type contact.
    3) Over wearing syndrome, ( pain or discomfort sometime (30 min to several hours) after removal of lenses.
    Chip,

    I'm curious. The ide a of #1 was relevant in the days of PMMA and central corneal clouding wehr ethe edema is mor focal. In today's contact's, edema is more generalized over the whole cornea such that retroillumination, even direct observation may be difficult to detect stromal or epithelial edema. In other words, even keratometry or topography might not pick it up.

    Of course, where edema is greater than 15% change you will see edema form the onset of endothelial folds. Punctate bullous keratopathy will occur when the cornea has increased by 25%.

    In t hese cases, subtel changes can be detected with a pachymetry although I believe that it takes 50 nm of change before I would presume edema.

    In chronic edema which is most consistent with soft lenses, limbal anoxia and their change in vasculature is revealing.

  17. #67
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    Quote Originally Posted by chip anderson View Post
    and since this isn't taught in school any more, tell the patient the purpose of soap is to mix oil and water.
    They taught that at my school! (Graduated HS in 2002)
    (This is really off-topic, but that is exactly why I think shampoo and conditioner in one doesn't make any sense. You're most likely just going to wash out the conditioner and leave the oil in your hair.)
    LOL...I guess I just had to reply to that because I was surprised to see someone else who knew exactly what soap is.

  18. #68
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    no longer playing in this sand box
    Last edited by HarryChiling; 02-21-2007 at 04:50 AM.
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  19. #69
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    Kinda reminds me of the paper I submitted to the CLSA a few years back titled: Sam and Lars- evil twins? It was about the dependance on acronyms to remember simple optical principles. Left add, right subtract for toric axis compensation. Are you kidding me? As a learning tool, maybe, but it's irritating to see it published in trade journals and optometric journals. Someone who has done 5000 refractions needs to know "LARS?"

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    Last edited by HarryChiling; 02-21-2007 at 04:50 AM.
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    Hello all,

    I am new to OptiBoard, and I am wondering if anyone out there can clue me in as to what I should be expected to know for the upcoming NCLE exam on Nov 19. I am working with CLSA's Contact Lens Manual, as well as the CLSA's Test Review (200 sample questions w/answers), but I find that the Test Review questions are far easier than some of the concepts in the CL Manual.

    I spoke to the Test Manager at the NCLE, and she said that if the concept seemed too in-depth for a multiple choice exam where you cannot use a calculator...it is probably not covered in the examination.

    Can anyone give me some pointers based on first-hand knowledge? It would be very much appreciated.

  22. #72
    ATO Member OPTIDONN's Avatar
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    Pay close attention to RGP fitting and modification.

  23. #73
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    thanks Optidonn....

    Are there contact lens history questions too? :hammer:

    lol

  24. #74
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    Don't bother with history (for this exam anyway) most people making up the exams don't even know the history back to the '80's much less when the the early work was done from 1900~1960.
    Tests are more on how to keep inventory in a doctor's office than history.

  25. #75
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    Quote Originally Posted by Snitgirl View Post
    thanks Optidonn....

    Are there contact lens history questions too? :hammer:

    lol
    Hey there are alot of people who are suprised by the amount of RGP questions asked and don't pay the amount of attention that they should to this...your mean

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