Contact Lens Fitting Exam and Evaluation Protocols/Checklists

Hi,

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Is this still done at the states or outdated already by superior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
defaults.

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
solution?

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

 

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
professionals.

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)

 

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

 

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

http://www.amazon.com/Clinical-Manual-Contact-Lenses-Bennett/dp/0781778298/ref=pd_rhf_p_t_1

Pia

The search is over

 

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)

 

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
hour).

 

Pia schreef:

Major snip...............

An optometrist without a slitlamp?

Jan (normally Dutch spoken)

 

Maybe they don't have them in a third world country like the
Philippines.

 

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

 

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..
measurement
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
locally
practiced.

Slit lamp is quite expensive... and only veterans optometrists use
slit lamp. How can the beginner optometrists afford to buy a slit
lamp.

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

 

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
expert.

 

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

 

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.
This
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

 

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!