Contact Lens Fitting Exam and Evaluation Protocols/Checklists

Discussion in 'Optometry Archives' started by Pia, Mar 1, 2009.

  1. Pia

    Pia Guest


    I'll look for a third optometrist tomorrow and want complete
    checklists so she won't miss anything. My first optometrist
    didn't use florescien pattern for tear inside contacts
    evalution nor the 2nd who didn't even use trial lens.

    So I need to equipt myself with full knowledge of how to fit
    lens so I won't be fooled again by lazy and inefficient
    optometrists. I live in a country where RG lens is rare and
    many optometrists haven't touched one (literally).

    Checklist review:

    1. Florescein pattern to test for tear performance between lens/cornea

    Is this still done at the states or outdated already by superior
    Topography data which some doctors may take total
    confidence in?

    2. Lid Fitting and Design

    The lens should be in between my eyelids so that if I have small
    eyes, the lens should be small and not go beyond the eyelid, right?

    3. Optical Zone Diameter

    I heard that optical zone diameter encompass anything from 65%
    to 80% of the lens diameter. But most commercial RGP only
    make you choose base curve, diameter, power. How could you
    know its optical zone diameter?

    I read the following: "Select an optical zone diameter equal to
    the base curve radius in millimeters. In other words, a 41.75D
    (8.09mm) base curve radius would be accompanied by an OZD
    equal to 8.1mm, and a 45.50 D (7.42mm) base curve radius
    woudl be accompanied by an optical zone equal to 7.4mm.

    4. Base curve radius.

    Quote: "The primary purpose of the base curve radius is to
    optimize the fitting relationship of the lens to the central and
    midperipheral cornea. The base curve radius to be selected
    depends on several factors, including corneal curvature,
    the observed fluorescein pattern, and the desired lens-to
    cornea fitting relationship"

    Also something about a Cyl of 1.0D needing to make it
    flatter "on k" by 0.5D

    5. Peripheral Curve Radii/Width

    I wonder if the lens can be manufactured with custom values or

    Although I use gas perm for 20 years. Starting years ago. I
    noticed that in a dusty place, I always get particle inside my
    eyes and make me tear. That is why I only wear gas perm
    5 hours or less a day.

    Right now. I should have preferred soft contacts but according
    to the opthalmologist, from 1 to 10. My eyes dryness is at 7.
    Can Silicone Hydrogels help? or is Gas Perm lens the only

    Also is the Corneal Topography accurate enough that
    fluorescein screening can be bypassed just like what
    the second optometrist did? Or I heard there is a
    software that can make a virtual fluorescein simulation
    based on the Corneal Topograpy data. Maybe in
    my country, fluorescein tear layer in contacts evaluation
    is not used at all?

    6. Tear Layer Power

    So it's better to always get lens at flatter than K by
    0.25 D to prevent edge closure?

    What else to look for. And what commercial RGP
    can make you order with full sets of data? In my
    country, we don't need prescription to order any
    RGP. I order mine several times for the past 20
    years without any prescription. But only base
    curve, diameter and power is asked for as one
    can't specify optical zone diameter for example
    and optometrists don't have the power to specify
    them either.

    Some doctors here not want to tell me what is in
    the Corneal Topography but don't worry, i'd still
    look for an optometrist who would be the one
    to actually fit my lens. But I just want to know
    how to read the Topography like knowing how
    many point samples it used, etc. So please tell
    me asap. Thanks.

    Pia, Mar 1, 2009
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  2. Pia

    Jan Guest

    Pia schreef:

    several snips made..........
    First of all if you'r still wearing your RGP lenses at this very moment
    it's impossible to perform a perfect refit.

    BTW, wich country do you live in?
    Still done despite the topography wich is very very helpfull for trained
    Not always.
    Nowadays RGP lensdesigns are very often off an asperical backcurve type.
    Meaning no OZ.

    Your professional have the knowledge to decide.
    In RGP fittings absolutly not!!!!

    Or I heard there is a
    Nothing more nothing less a theoreticaly image.
    Gives you an idea but not neceseraly the real image seen by the
    fluorescein test.

    There is more to know.

    It looks like you want to fit your RGP lenses yourselfes, this is
    simply not possible.

    Jan (normally Dutch spoken)
    Jan, Mar 1, 2009
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  3. Pia

    Pia Guest

    I stopped for one week already because one of them got lost.
    I keep thinking about going to soft contacts but it seems to
    have significantly higher risk. For example. How do they manage
    tear exchange in the big diameter lens like 14.2mm in the Focus
    O2Opiks Silicone Hydrogels? If there is already problem using
    a 10mm RG lens. What more if the diameter is 14.2mm. How
    do you think tear exchange work in the 14.2mm soft contacts?
    Somewhere in Asia.

    Know how I can check lid tension myself so i'd know whether my
    lid is flexible or stiff.
    You mean modern lens has no optical zone? Or do you mean the entire
    lens is the optical zone?
    But my professionals don't own any fluorescein screener
    and some don't even have trial lens because only rare
    number of people get RGP lens in my country so we can
    say some have practically no experience in RGP lens.
    No exaggerations.
    In two threads below. I shared my Corneal Topogaphy.
    Can one get the base curve from the Mean Power there
    (in the case of the OD 43.7D and OS 43.8D)?
    No. But since many optometrists in my country only focus on
    eyeglasses and have minimal experience in contact lens
    especially gas permeable. I have to be informed and aware
    of things so as not to be duped.

    Pia, Mar 1, 2009
  4. Pia

    Pia Guest

    For those who are lost in seeking a correct contact lens fit.
    I spent a day prioritizing the search for the right optometrist
    to get a correct prescription. I saw 6 optometrists. but didn't
    continue with most of them because they didn't have any
    slit lamp nor fluorescein dye. They said its expensive to own.
    Since the free chapter in a contact lens book at amazon
    says the fluorescein dye would be the deciding factor in
    getting a right fit (for uniform tear binding). I look all over
    the city for a doctor with a fluorescein dye. At last I found
    one (and only). After a second Corneal Topography and trial lens/
    fluorescein dye exam. I finally got a final base curve of 7.8 for
    both eyes and 9mm and ordered a pair. I asked her about the
    calculations. What the previous doctor who gave me a prescription
    without even giving me trial lens did was simply add the min and max
    in the simple K, divide by 2 and get the base curve in mm
    which is 7.75. So I guess that most of the time, Corneal
    Topography results is close to the values in actual fit. I
    wonder if United States optometrists would agree to this.
    Corneal Topography took thousands of sample points
    compared to just 2 in the manual keratometer. So the
    thousands sample points would be pretty accurate and
    can mean equal fluorescein dye pattern in an actual
    exam especially if 9mm diameter is chosen and if the
    choice or parameters patients can order is only base
    curve, power, and diameter in a gas permeable contact
    lens which is true in my country.

    I found the information I seek about the fluorescein dye, etc.
    from a contact lens book at amazon where you can
    read the entire free chapter 5 called "Lens Design, Fitting and
    Evalution" at


    The search is over
    Pia, Mar 2, 2009
  5. Pia

    Jan Guest

    Pia schreef:
    Major snip....................
    Yes and that's why they could afford the much cheaper instruments like
    the Orb and the Zyoptic, you make me laugh.

    I suppose you have a great thumb Pia

    another major snip.

    I can imaging that...........

    Jan (normally Dutch spoken)
    Jan, Mar 2, 2009
  6. Pia

    Pia Guest

    The Orb and Zywave is owned by a corporation with dozens of
    opthalmologist and one main optometrist. It was he who prescribed
    me 7.75 base curve without even putting trial lens. When I asked
    him why. He said he is sure that's why no trial lens and fluorescein
    pattern and just made me order a pair.

    The other independent optometrists in the mall and city don't have
    any slit lamp or fluorescein dye because they didn't invest in them
    due to small amount of gas permeable users in the country.

    Yesteday. I went to a second corporation who dozens of doctors.
    There I found one using slit lamp and fluorescent dye with corneal
    topography. I spent 2 hours or more with her as she said it is
    common to spend 2 hours with one patient for many trial fit and
    dye scan. Therefore it explains why the previous optometrist just
    gave me prescription without any tests.. because with 30 patients
    a day. He has just no time. I wonder if optometrists in the US
    like Mike Tyler also spent 2 hours with each patient for complete
    test (remember one has to wait 20 mins for trial lens to settle down
    and if there are many trials.. waiting in the middle would take a
    Pia, Mar 2, 2009
  7. Pia

    Jan Guest

    Pia schreef:

    Major snip...............
    An optometrist without a slitlamp?

    Jan (normally Dutch spoken)
    Jan, Mar 2, 2009
  8. Pia

    Charles Guest

    Maybe they don't have them in a third world country like the
    Charles, Mar 2, 2009
  9. Pia

    Pia Guest

    Yes, I live in the Philippines. I only found 2 optical centers to
    have slit lamp and fluorescein dye, Asian Eye Institute and
    American Eye Center. The rest only have refraction or
    autorefraction machines especially in optical shops in the
    mall or private practionioners who can't afford millions to
    buy them and having only 1 RG lens customer a month.
    Also since soft contacts with adaptive base curve and
    disposable lens are the norm. Who needs slit lamp or
    fluorescein dye.

    Asian Eye Institute has 10 opthalmologists with different
    specialies like glaucoma, retina, catract and only one
    who specilize in low vision. That is why he didn't put me
    in any trial lens or fluorescien evaluation because he has
    over 30 customers a day and don't have time to spend
    2 hours for each. While at American Eye Centers they
    have 10 optometrists who go through procedures hence
    I was able to spend 2 hours with one of them to have
    the confidence of a precision fluorescien pattern
    evaluation for uniform tear distribution.

    Also I think manual keramatomer is not accurate or they need
    skilled practioners. The first optometrist I saw who prescribed
    me 10mm diameter RG lens and told me I had GPC (which
    I don't) only used manual keratometer and got a reading
    of 7.95 base curve when 2 Corneal Topography shows reading
    of 7.75-7.8 base curve which is what I got.

    Anyway. The last optometrist told me that it would usually take
    3 months after taking off gas permeable lens used for 15 years
    for the cornea shape to get back to original. Is this true??
    Could it be because I've used 7.8 base curve for the past
    20 years that they also measure 7.8 in the Corneal Topography
    because somehow the rigid gas permeable is able to reshape
    the cornea which takes 3 months to get back to normal? In
    their Lasik requirement. One must not wear any rigid gas
    permeable for at least 3 months before one can have accurate
    shape of the cornea. Is this concept also practiced in US
    optometry and lasik clinical setting or is this a myth belief only
    by local opticians?

    Pia, Mar 3, 2009
  10. Pia

    Pia Guest

    Of course opthalmologists use slit lamp but optometrists as I know
    only measure diopters in myopia, hyperopia and presyopia (that
    is why it is called optometrist.. opto.. metrist.. metric..
    of opto or optical). Anything about the organic eye is refered to
    opthalmologists... at least as locally practised.
    Since almost all soft contact lens are disposable and the base curve
    is adaptive. Why do they have to examine the patient eye using slit
    lamp since all curves can fit the eye. If uncomfortable, then getting
    a flatter base curve would be the order of the day.. this is as
    Slit lamp is quite expensive... and only veterans optometrists use
    slit lamp. How can the beginner optometrists afford to buy a slit
    If topography and fluorescein is ok, the mechanical part of contact
    lens fitting is solved, the rest is nervous system related and it can
    be adjusted mentally or if immune related.. then the patient simply
    has to go back to eyeglasses. I'm only concerned about the
    mechanical fitting since I know I can wear gas perm having
    worn them for 2 decades.
    What I mean to say is. For LASIK patients. All local doctors only do
    final corneal topography if the patient at least stopped wearing
    gas perm for 3 months because the cornea is still not in original
    shape. They say it takes 3 months for cornea to get back to
    original shape. Is this not the concept in the US too? Do they
    let patients wait for 3 months to mentally prepare and not to
    wait for curves to get back to original? The last optometrist also
    told me that if I don't wear gas permeable as soon as possible
    or change to soft contacts, the astigmatism may slowly get
    back in a few months (If I had one 20 years ago) when
    the eyes slowly gets back to original shape. What you said
    before was that the cornea gets back to original shape
    in as little as one day?? Can you confirm it again?
    There is no case where the cornea slowly
    gets back to original shape after 1 month or 2?? Any
    study that refute this?

    Pia, Mar 3, 2009
  11. Pia

    Dan Abel Guest

    You are a very patient person, Mike. I killfiled Pia a few days back.
    I've seen this behavior on other groups. It seems like there might be a
    language problem at first, but then it appears that the misinformation
    gets communicated just fine. It's the initial questions that don't have
    enough information to provide a complete answer.

    Pia needs to see a mental health professional, not a vision
    professional. I'm not surprised that the vision professionals that she
    has seen, have not been able to help her. There are valid reasons for
    getting a second, or even a third opinion, but most people who are
    unhappy with their first opinion try to find a more qualified person for
    later opinions. It sounds like Pia is cruising the malls looking for an
    Dan Abel, Mar 3, 2009
  12. Pia

    Pia Guest

    That's uncalled for. Anyway. I got most answers I want already.
    It all started when I lost one of my gas perm 2 weeks ago and
    I was deciding whether to change to soft.. but local optometrists
    told me my myopia would get worse because gas perm was
    supposed to stop progression... which was refuted by US
    expert Mike Tyler. Then when I plan to return to gas perm
    due to significant more health risk for soft contacts and
    get a correct base curve, the optometrists didn't perform the
    correct standard operating procedure like using slit lamp, trial
    lens and fluorescein dye. Well. If I live in the US, there would
    have been no problem. But here in my country, I can order
    any lens without prescription. In fact, for the past 20 years,
    I ordered gas perm 7 times without any prescription of
    measurement done. I only got one last week after 20 years.
    Thanks Mike Tyler for the answers and for demonstrating
    superior US world class eye care.

    Pia, Mar 3, 2009
  13. Pia

    Pia Guest

    That explains it. In my country, there are so many opthalmologists and
    many have only few patients like 2 or 3 a day. That's why all eye
    related problems are automatically refered to opthalmologists and
    optometrists have only very limited compartmentalized job which
    is to prescribe glasses and occasionally make contact lens fitting.
    explains why the 2nd optometrist I saw couldn't even differentiate
    between eyelid infection and calcium deposit and I have to look
    for the country top opthalmologist to make the diagnostic. But
    even among opthalmologists. It's also compartmentalized, 2 days
    ago I saw this opthalmologist specializing in glaucoma and
    cataract and show her the Corneal Topography and Abberometer
    reports. She said she couldn't understand them because she was
    not familiar although she can answer any question about
    glaucoma and cataract. So next time you deal with a person
    who lives in third world country. You should understand where
    they are coming from.

    Thanks for the superior answers for the questions below. You
    have given an excellent perspective for them.

    You must be one of US greatest optometrists with multidisplinary
    training and a model for other optometrists around the globe.

    Pia, Mar 3, 2009
  14. Pia

    Neil Brooks Guest

    Though I've never /seen/ Mike, I've been to LOTS of eye doctors, and
    I've been reading Mike for years.

    He is, indeed, one of the good ones!
    Neil Brooks, Mar 3, 2009
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