NCLE Help

**Optician Magician** · 10-25-2007, 06:48 PM

I would love to hear any tips on taking the NCLE. What should I focus my studies on... am I wasting my time focusing on certain things... :hammer:

Any kind of advice would be appreciated! I really want to do well, but am unsure of the difficulty of the questions that will be asked. So if you've taken it, I would love some examples of the questions! :D

Thanks!!!
:cheers:

**CAR** · 11-03-2007, 03:42 PM

I am also going to take the NCLE. The only thing I heard is that there is a lot of anatomy on it.

**chip anderson** · 11-03-2007, 07:49 PM

There's a lot of bookkeeping and inventory management on it too, I don't think it should be , but it's there.

Chip

**CAR** · 11-04-2007, 07:54 AM

Chip -- thanks for the reply. Are you saying there's stuff from accounting (debits/credits, income statements, balance sheets), fifo, lifo etc?

**Optician Magician** · 11-04-2007, 11:42 AM

Thanks for the tips! :) GOOD LUCK CAR!

**Optician Magician** · 11-04-2007, 11:56 AM

Question???
A Pt. wearing a 43.00D base curve, 9.0mm diameter, 7.0 Optical Zone diameter requires a change to a 9.5mm diameter with a 7.5 OZ diameter. To keep the base curve corneal bearing relationship the same, the new base curve would need to be....?

A) 42.50 B) 42.75 C) 43.50 D) 43.75

Please explain your answer, this problem has stumped me for some reason. I know that if you increase diameter you are making the lens tighter and it would require the base curve you to flatten the base curve to make it looser... but how much? I can't seem to find a rule of thumb.
Thanks! :hammer:

**optigrrl** · 11-04-2007, 12:00 PM

Study up on the solutions, my test was all about the lens solutions.

**chip anderson** · 11-04-2007, 02:09 PM

Accounting was more on how to keep cl & opthalmic inventories which seems to be all the "authorties" think opticians are capable of now.

**tmorse** · 11-04-2007, 10:05 PM

Originally Posted by Optician Magician

Question???
A Pt. wearing a 43.00D base curve, 9.0mm diameter, 7.0 Optical Zone diameter requires a change to a 9.5mm diameter with a 7.5 OZ diameter. To keep the base curve corneal bearing relationship the same, the new base curve would need to be....?

A) 42.50 B) 42.75 C) 43.50 D) 43.75

Please explain your answer, this problem has stumped me for some reason. I know that if you increase diameter you are making the lens tighter and it would require the base curve you to flatten the base curve to make it looser... but how much? I can't seem to find a rule of thumb.
Thanks! :hammer:

Many nomograms have a 'rule of thumb' that for every 0.5mm of diameter change, adjust the base curve by 0.25D. Thus a lens diameter change from 9.0mm to 9.5mm would require a corresponding base curve change of 0.25D flatter. So with 43.00 original base curve, the larger 9.5mm diameter lens would need a 42.75 base curve.

Having said that, some CL nomograms suggest a 0.10mm (0.50D) change in base curve for 0.5mm Diameter change. And many CL authorities say that you need to make a 0.10mm (0.50D) change in base curve before you would notice any change in fitting charateristics, which would suggest 42.50D as the answer. So go figure.:hammer:
Nomograms only claim to work 80% first fit anyway. This is one of the reasons that a trial fit with trial lenses is the best way to fit RGP's. Oops, here we go again;)

**chip anderson** · 11-04-2007, 10:16 PM

.02 or less can make a great deal of difference in a rigid lens fit. In a soft one you need ten times this to notice any difference. Hense rigid lens fitting is more demanding.
The diameter of the lens does not make as much diffence in the fit so much as the posterior optical zone. If this gets larger with the diameter increase then the fit is changed. If this is gets smaller even though the diameter is larger the fit sagital depth may not be increased but actually decreased.
The design and radus of the peripheral curves can have much more effect on the fit ( a forgotten art) than the base/power.

Chip

**tmorse** · 11-04-2007, 10:55 PM

Originally Posted by tmorse

Many nomograms have a 'rule of thumb' that for every 0.5mm of diameter change, adjust the base curve by 0.25D. Thus a lens diameter change from 9.0mm to 9.5mm would require a corresponding base curve change of 0.25D flatter. So with 43.00 original base curve, the larger 9.5mm diameter lens would need a 42.75 base curve.

Having said that, some CL nomograms suggest a 0.10mm (0.50D) change in base curve for 0.5mm Diameter change. And many CL authorities say that you need to make a 0.10mm (0.50D) change in base curve before you would notice any change in fitting charateristics, which would suggest 42.50D as the answer. So go figure.:hammer:
Nomograms only claim to work 80% first fit anyway. This is one of the reasons that a trial fit with trial lenses is the best way to fit RGP's. Oops, here we go again;)

Opt. Magician... Cl companies spend a lot of time and money coming up with their own CL fit nomograms, so use the nomogram that is provided for that particular CL material chosen.

I don't agree with Chip that 0.02mm or less would result in any meaningful fit changes.. Consider that Base curve tolerance is 0.025mm. Chip...OPt. Magician is looking for assistance in his NCLE exam.

Although nomograms can differ noticeably between companies, Polymer Technologies with their Boston series of lenses have used the 0.25D base curve to 0.50mm diameter 'rule of thumb' in many of their lens nomograams, based on a multitude of fits in a lot of CL studies, so use it. Remember that K readings are inherently flawed since they measure only the central 3mm of the cornea, but you are fitting an area 6-8+mm out. When you get as much CL experience as Chip, you can then develop your own fitting procedures. :cheers:

**Snitgirl** · 11-05-2007, 04:47 PM

What contact lens books do you own?

Originally Posted by Optician Magician

I would love to hear any tips on taking the NCLE. What should I focus my studies on... am I wasting my time focusing on certain things... :hammer:

Any kind of advice would be appreciated! I really want to do well, but am unsure of the difficulty of the questions that will be asked. So if you've taken it, I would love some examples of the questions! :D

Thanks!!!
:cheers:

**Diane** · 11-05-2007, 07:01 PM

The Job Analysis from CLSA in the front of the Contact Lens Manual test review shows exactly what is required to know on the exam. Contact the Contact Lens Society of America. In addition, you need to be very familiar with the metric system. That's where a number of mistakes occur.

Diane

**Optician Magician** · 11-05-2007, 07:32 PM

Many nomograms have a 'rule of thumb' that for every 0.5mm of diameter change, adjust the base curve by 0.25D. Thus a lens diameter change from 9.0mm to 9.5mm would require a corresponding base curve change of 0.25D flatter. So with 43.00 original base curve, the larger 9.5mm diameter lens would need a 42.75 base curve.

Tmorse... Thanks! This makes more sense to me now. In the Contact Lens Manual it describes the fitting relationship on page 204.... " Every 0.05mm change in radius corresponds to approximately 0.25D change in power." but it didn't seem to make sense to me... your 'rule of thumb' does! Thank you!

Also, Snitgirl...
I have the Contact Lens Manual vol. #1 and the Review guide that goes along with it. They are the books that everyone suggested I read before the exam. Do you have any other suggestions?

Thank you all for your help!:p

**chip anderson** · 11-05-2007, 07:33 PM

The real secret to the metric system is: "Don't bother trying to convert it to whatever you are familiar with." As long as you think of meters as meters, millimeters as millimeters it's really easy to work with. Easier than inches and feet actually. It's went you try to think of an inch as 2.54 centimeters or a meter as 36.9 inches that you get confused.

Chip

**tmorse** · 11-05-2007, 11:40 PM

Originally Posted by Optician Magician

Tmorse... Thanks! This makes more sense to me now. In the Contact Lens Manual it describes the fitting relationship on page 204.... " Every 0.05mm change in radius corresponds to approximately 0.25D change in power." but it didn't seem to make sense to me... your 'rule of thumb' does! Thank you! :p

Sorry Magician... your thanks seem premature... Without checking your CLSA reference, I think your example at page 204 is referring to the SAM and FAP rule for changing Base curve and then adjusting final lens power to compensate for your different tear lens power produced by this change.

But we were discussing only changing a lens diameter and then adjusting the base curve of the CL to still keep the same fitting characteristics, without taking later required CL power adjustment into account.
So the order is... the final base curve is determined after diameter change, THEN we must ALSO adjust the CL POWER ordered to compensate for this new tear lens produced. This new tear lens is produced by your choice of new base curve on the 42.50D flat K cornea.

eg. a 42.50 Flat K is fit with a 42.00 base curve with dia 9.0mm. Everything works with a -1.00D lens power, but the CL dia is too small.

You decide that you want to fit a 9.5mm dia. Well this 0.5mm larger dia lens requires a base curve adjustment of 0.25D flatter to 41.75D. The original tear lens using the original 42.00 BC was -0.50D and your original
-1.00 CL power was perfect.
ie. your needed -1.50D total power to see well and the tear supplied
-0.50D. So your final CL lens power needed was -1.00D as measured with a lensometer. -0.50D + (-1.00D) = -1.50Dsph

But with a new base curve of 41.75D your tear lens when fit on flat K of 42.50D is now only -0.75D. But you still need final lens power of -1.50D to see well. So your now you must add -0.75 in your final lens power with this 0.25 Flatter base curve . Thus -0.75D final lens power will combined with your -0.75 tear lens to produce the needed -1.50D.

In other words you fitted base curve 0.25D flatter, so final lens power must be adjusted according to the FAP (flatter-add-plus) rule. Base curve choice of 0.25 Flatter means your must adjust final CL lens power by the same amount, +0.25D. This added to the -1.00 original CL lens power that worked for a 42.50 Base curve is now only -0.75sph.
ie. -1.00 + (+0.25) = -0.75Dsph.
So now the -1.50D final power needed is composed of -0.75 tear lens and the -0.75 CL final power ordered. And the total power achieved is still the required -1.50D.

Of course we convert the base cuve in D. into mm. of curvature when finally ordering the base curve from the lab.

It can be confusing! :D

**chip anderson** · 11-06-2007, 07:13 AM

For most common base curves, it's .04 mm. per quarter diopter.

In some of the very flat ones, it's more, in some of the very steep ones it can be less.

Chip

**Optician Magician** · 11-06-2007, 02:35 PM

Tmorse,
The CL manual didn't give me a fitting relationship between diameter and base curve that I could find... the only fitting relationship I could locate referred to the radius of curvature and power, so I was trying to find some way to use it to answer my original problem... I was thanking you for the helping me understand that I was doing something needlessly... diameter and base curve was obviously the relationship that I needed to understand and you and chip have helped me greatly! You guys are terrific! :-)

**Optician Magician** · 01-17-2008, 11:51 PM

:p
I just wanted to thank you all for your help! Did I overstudy or what??? I was expecting a much different exam, I guess I thought it would be similar to the NC contact lens exam. Anyway, thanks again! Everyone's advice was really appreciated. I am so happy to have my NCLE! :D

**Fezz** · 01-18-2008, 06:36 AM

Bravo Optician Magician!!!!

Way to go!!!!

:cheers::cheers::cheers:

**mjacob** · 02-23-2008, 02:04 PM

Originally Posted by Optician Magician

:p
I just wanted to thank you all for your help! Did I overstudy or what??? I was expecting a much different exam, I guess I thought it would be similar to the NC contact lens exam. Anyway, thanks again! Everyone's advice was really appreciated. I am so happy to have my NCLE! :D

CONGRATS!!!! I guess, u might be reall excited since u just have to worry abt the state boards now, right? I'm planning to take the NCLE on this MAY 08'!! I'm studying frm the wrkbk&cd set frm the OTI- Exam prep. for Contact Lens Dispensers! Can u tell me what kind of ques's where on it and what should i be focusing on? Rightnow, i'm having some trouble finding the radius of curvature! Any help and advice would be appreciated. Thanks!!!

**HarryChiling** · 02-23-2008, 06:00 PM

Originally Posted by mjacob

CONGRATS!!!! I guess, u might be reall excited since u just have to worry abt the state boards now, right? I'm planning to take the NCLE on this MAY 08'!! I'm studying frm the wrkbk&cd set frm the OTI- Exam prep. for Contact Lens Dispensers! Can u tell me what kind of ques's where on it and what should i be focusing on? Rightnow, i'm having some trouble finding the radius of curvature! Any help and advice would be appreciated. Thanks!!!

Finding the radius of curvature would be:

n_i = index of surrounding medium
n_r = index of refracting medium
D = dioptric power
r = radius of curvature in meters

r = ( n_r - n_i ) / D

There you go now if you are converting a keratometer reading from diopters to radius you will need to know that the keratometer uses the index of 1.3775 for it's index and the index of air is 1:

r = (1.3775 - 1) / K's

Now to simplify things for contact lenses we would need to convert this measurement to mm instead of mm to 1m = 1000mm so we need to multiply our equation by 1000 to convert it into mm

r = [(1.3775 - 1) / K's ] * 1000
r = (0.3775 / K's) * 1000
r = 377.5 / K's

Now that's what you remember going into the test that to convert K's to radius.