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Thread: Contact Lens Education

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    I had hoped to start a whole contact lens forum, but Steve feels this would not have enough interest. So I plan to start a string which will be to impart general knowledge of contact lenses. I seem to know quite a lot about rigid lenses an don't really think soft contact lenses require much intellect so I will to try to place a few posts each week starting with the more basic things of rigid contacts working to some of the more intricate ones. Will be happy to respond to anything anyone has to ask or say on the subject.

    Chip Anderson, FCLSA

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    Bad address email on file stephanie's Avatar
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    Great idea Chip!! I for one am interested. I found a lot of the information on this board helped me with the ABO and am hoping it will help with the NCLE. Did you do this just for me?? I barely know anything about them except what I am currently learning.
    Have a great day!!
    Steph

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    Master OptiBoarder Darryl Meister's Avatar
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    Sounds like a great idea, Chip. Maybe we should do the same for spectacle lenses.

    Best regards,
    Darryl

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    Lightbulb

    Dear Uncle Chip,
    Your ideas is fantastic!! PLease go ahead I for one would study your tread.
    Thanks You.
    Sara

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    Redhot Jumper

    Of course, in Nairobi, uncle means 'old dude'.... :D Just kidding Chip. You do give off that avuncluar vibe, though.
    Tip to Sara - never ever mention ethics in dispensing, particulary not in relation to Drs filling their own prescriptions. You'll never shut him up :)
    Seriously, it's nice to have input from a new country, and I'm a student too, so we can ask the masters questions together.

    Maria

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    O.K. here it is, the first posting. I suppose I will start with what you should do when dispensing rigid contact lens to the patient. Teach the patient to wash his hands with a soap that does not contain oil, I always recommend: Ivory Bar for both rigid and soft contacts as it contains only soap, and since this isn't taught in school any more, tell the patient the purpose of soap is to mix oil and water. There by removing the oil and dirt with rinsing.

    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. When I had been in the business about six weeks I and we had only PMMA then, I found that polishing lenses would be a major part of my life. I spent five years interviewing five thousand patients on handleling and found that 99 out of 100 who handled their lenses over the sink (even with a towel over it) had scratched lenses. This was amazing because 80% of these will tell you "But I never drop one."

    Stay with the patient an teach him to insert and remove his lenses (without the use of any anesthetics. Have him do it in your presence until you feel he can, do not allow him to take the lenses home with him if you don't think he can do this. Do not allow anyone else to do this for him except in the cases of the very young and the senile. If someone else will do this, the patient will never learn to do it by himself.

    Teach the patient to clean, disinfect and store his lenses. No matter what the instructions say, tell the patient to scrub his case out weekly with a tooth brush and Johnson's Baby Shampoo. I know that the solution manufacturers want daily replacement of solution, I don't care too much about this but I want all dirt and cultures scrubbed out weekly.

    enough for now, Chip

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    We get taught that they should use CL solution, instead of baby shampoo, for cleaning the case. Is that worse, better of the same?
    Maria
    PS You are a bit like Master Yoda, with a little Mr Miaggi thrown in. :) Squish! Just like grape.

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    Also we get told that lenses should never touch ordinary water, because of all the crap that's in it. Is this what you think? Or do you think it's ok?

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    As to water (in regard to rigid lenses at least), I think it's just fine for rinsing lenses. I do know a lot of experts and biochemist opthalmologist who disagree with me. However that same old tapwater is exposed directly to the eye in the shower and if the bugs gonna get you. It's gonna get you. Now as to growing bugs in the case, I take this very seriously and think Johnson's Baby shampoo is much better than contact lens solution for cleaning the case. This upsets Johnson's but who cares?

    Now as to a real source of eye infection: Wetting the lens with saliva. This can be cured in most cases by asking the patient to hold out his hand and close his eyes. Put an artificial eye (preferably in his color) in it and tell him this is what he is taking a chance on. You can even tell him he never had an "emergency" worth taking a chance on that.

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    My insight on Solutions:
    Rigid PMMA lenses. Soaking solutions should be strictly a soaking or a combination soaking/cleaning solution. Wetting/soaking solutions should not be used. The gum~up the lenses and case. I used to have two compeditors, one recommended dry storage the other used the only combination soaking/wetting solution on the market at the time. Both had patients who ended up in my office and were "cured" when I buffed the encrusted solutions or dried on proteins off the lenses. The encrustations looked so similar that in RGP Lenses I often think a great many of our troubles are caused by the fact that combination wetting/soaking solutions are all that is available for them.

    Also I shudder to think how many unsuspecting souls have been sold new lenses when all the old ones needed was the deposts removed (mostly from the posterior surface).

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    Rigid Lens Inspection

    This is why you are entitled to a mark~up on rigid lenses. Regardless of what the FDA says or feels on this subject this is how you earn your salt as an optician/contact lens technician. Those who feel that they can say: "I trust my laboratory, will find that they are very wrong once they institute these practices.

    1) Check the central posterior (base) curve of every lens. This may be done with a keratometer or a radiuscope or several automated devises. Tolerances should be no more than .02 mm (1/8 diopter) and no, this does not double for torics or bifocals.

    2) Check the power (focal length) with a lensometer or automated devise. This should be withing 1/4 diopter+or- and should not be + on ½ of a pair and - on the other half.

    3) The diameter should be checked with a measuring magnifier or a sliding diameter gauge. Tolerance should be .10 mm or less.

    4) Check the thickness. This may be done with a thickness gauge or a lens clock. To use a lens clock place the lens on a flat surface and place the lens clock with the movable pin on the lens, it reads in 1 mm. increments.

    5) Check the edge design with a measuring magnifier, this may also be profiled on some lensometers by holding the lens on the mirror(movable) at an angle 90 degrees from that for power and focusing near plano.

    6) Check the surface quality, with a measuring magnifier and/or a radiuscope. Tolerance on lathe marks, casting marks, tool marks,

    7) Check the optics: Should be done with both the lensometer and by holding lens at arm's length and viewing a flourescent tube through the lens. The lens should be moved and rotated, you will be amazed at the waves, rings, and other aberrations that appear with this technique.

    8) Check the color.

    9) There is not a whole lot you can do about checking the material, there are specific gravity tests for this but they are not a practical office procedure.

    If you can't or won't or don't have the equipment to do all of the above, the patient would be served equally well by purchasing lenses from Linda Carter, who can't tell one lens from another. If you do all of the above even on replacements, you can truly say you have earned your salt. Your lab won't love you but they will learn to respect you.

    Ole Chip
    Last edited by chip anderson; 10-25-2008 at 06:00 PM. Reason: 90 degrees

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    Bad address email on file stephanie's Avatar
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    Ok I have a couple of questions here that came right out of my book. Bear in mind that I do know the answer as I have the answer key. What I don't know is why?

    1. A contact lens has a base curve of 7.50mm. Its posterior peripheral curve would most likely be:
    A) 7.45mm
    B) 42.50 D
    C) 7.35 mm
    D) 30.00 D

    2. Of the curves listed which indicates the flattest base curve?

    A) 7.50mm
    B) 37.50 D
    C) 8.60 mm
    D) 49.00 D
    Like I said I do know what the answer is but I do not understand why.
    Thanks!!
    Steph

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    Stephanie:
    The answers to your questions are:
    1=D 2=B
    The reasons why are:
    Question 1
    7.45(45.37+or-) and 7.35(46.00-) are shorter in radius than the base (central posterior) curve. Any grinding of these curves to the base would touch in the center. 42.50(7.94 mm) is rather close to 45.00(7.50) and would not provide much relief at the periphery of the lens. In fact if ground into a 7.50 radius it would soon grind very wide and approach the center (trust me on this my first job in the contact lens industry was cutting an polishing base curves). Now 30:00 Diopters has a radius of about 10.0 mm (I think) and would grind into the periphery quite well and provide some relief for tear circulation and limbral clearance during movement. I would not chose this a peripheral curve on a lens of this radius myself, but it obviously would grind into the periphery.

    Question 2
    37.50 D= 9.00 mm.
    Try to think of any lens surface as having: less power as it grows longer in radius. This is true no matter what the lens is for or what it is made of.

    Now as to Base curve charts. Do you have a copy of Contact Lens Quarterly? If you do at the end of the "RGP/PMMA National Distributors" and before the solutions you will find a very good chart in every issue. Tear one out and put it with your reference materials. There is also a vertex (unfortunately a front vertex) chart on the same page. If you don't have a quarterly, let me know and I will E.Mail you a chart.

    Chip

    Chip

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    Bad address email on file stephanie's Avatar
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    Ah Chip!! I believe me book has some wrong answers. I have for the answers both as being B. Hmmmm... interesting. Well at least now I know when I question things it is usually with good reason. I don't have a chart as I have never had a reason to get the contact lens books. Thanks for all your help this has cleared some things up. At least til I get stuck again. Lord knows it is likely to happen any minute.
    Thanks Again!
    Steph"I am gonna end up in a rubber room before I am finished with cls."D

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    a

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    Hi everyone, new to this

    i have read valuable information on optiboard. i have a cls question

    the other day a guy came in for cls

    rx +5.25 -0.75 OU

    corneal cyl 0.75D

    did not want GPs or torics, wants for occasional use.
    heres the problem va with glasses 20/20
    sphere cls SE 20/40-3
    diagnostic mor +0.75 kinda helped.
    I just to see what power would give him 20/20, he needed +6.25 (since lenses go by .50 after 6.00... 6.00 va 20/20-3, 6.50 va 20/20-1)

    since this is a huge jump in power i have a call into the dr and am awaiting a reply as to what to do. can someone shed some light on this for me.

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    You might try a thicker lens, this will sometimes mask some cylinder. Also some aspheric lenses will "sometimes" help. Otherwise tell him GP, toric or live with it.

    This all asumes that the lenses fit and center of course. If the lens is too steep,
    (Checked by taking over the lens K's) if they are not crisp, go flatter).

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    thanks chip i knew i could get some good info from you
    i was thinking of trying a thicker lens but my main concern was the cl having to be +6.50 when rx is +5.25-0.75.

    keep up the good info

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    Originally posted by JJ:
    thanks chip i knew i could get some good info from you
    i was thinking of trying a thicker lens but my main concern was the cl having to be +6.50 when rx is +5.25-0.75.

    keep up the good info
    Well, there's the almost-half-diopter increase due to the vertex change... Your +6.50 contact has the effective power of a +6.00 spectacle lens. So, while there's a difference, it's not so humongous. And I'm assuming his specs fit normally (around 13mm); do they?



    [This message has been edited by shanbaum (edited 02-23-2001).]

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    Master OptiBoarder Shwing's Avatar
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    Actually, JJ e-mailed me with this question a few days ago. I suggested that s/he post it to Optiboard, whereeveryone could get in on the answers. I am glad to see JJ did!

    Actually Mr. Shanbaum took the answer right out of my mouth... And what was the vertex distance of the exam?

    Shwing;-}

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    While vertex is a partial explanation for the additional plus required, I would still check for a base curve too steep and expect it or cylinder requirement to be the reason for the fuzzy vision after adding the plus for vertex. And, while we are on the subject I have seen many, many hyperopes require much more plus than vertex would allow for after getting contacts. This plus is often not needed until 3 days to two weeks after being fitted with contacts. I think this is due to a latent hyperopia that shows itself after the patient relaxes whatever accommodation they may have.

    Chip

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    Chip,
    What do you understand by when you say latent hyperopia.
    In your opinion when fitting RGP lenses more importance you give to lens diameter or base curve.
    Checking on your views!

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    In response to your question, the base curve.
    This is a little like asking: "What size do you use?" I give the lab all specifications, diameter, base curve/s power/s, peripheral curves, optical zones, thickness, flange power. Anything applicable. I have been in the contact lens industry since 1958 at all levels, chances are I have more experience/knowledge of the subject than the little girl at the right~up desk, probably more than the consultant. And more importantly, I have the patient in hand the lab has never seen my patient.

    This does not mean that I will not seek out advise, but I try to make my own decisions good or bad and live and learn by my mistakes.

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    Bad address email on file stephanie's Avatar
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    You definately have more experience than this little girl at the desk. That is why I like to pester you to death with all my questions!! LOL!! I'll get all the info I can. Speaking of info. How can I order one of those cl books you spoke about? The doctor doesn't get that one and she would like to be able to get it too. Still studying don't know if it is getting me anywhere but I sure am trying like crazy. :)
    Have a great day!!
    Steph

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    I would like to make little contribution
    CLINICAL WISDOM FOR FITTING:
    1)Lens Diameter is the No.1 fitting parameter for rigid lenses,rather than base curve.
    2)Soft lenses are for today,hard lenses are for life.
    3)There is no such thing as a one lens fits all
    4)The perfect extended wear lens has not been invented.
    And lid eversion is a neccessary part of examination on every after-care visits(You all probably know why).



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