ABO test question

[gmc]

1 mm for every 2° of tilt, hence 8° retro since the OC is above the pupil.

[GAgal]

I luv ya Georgia girl but this is what's wrong with opticianry in the States right now imho.:o

==Upon further reflection this is easy to say from an old flatulent noise:)

Flatulence or not, I luv ya 2 Uncle Fester :bbg: You will always be my favorite crazy Uncle! I agree that multiple choice questions can sometimes be stacked in favor to the not so bright, but it is the best viable option that we have right now for the ABOC. Also, we need to remember, like the bright Braheem says,

People that want to succeed should be given the chance to slowly better themselves. I believe ABO-AC truly confirms you know your optics whrereas an ABO is a good steeping stone that leads to that certification.

The ABOC proves that we only have BASIC knowledge of the optical field. It is our mistake in the industry when we try to make the ABOC the ultimate in certification. Think of all the jobs that say, "must have a highly experienced, well trained and knowledgeable optician. ABO certification required." If they want all that, why does it not say ABO-AC required or ABOM required? One reason is because for many years the ABO was the certification to get because that was what the state or employer required. Another, there are not that many individuals with advanced certifications. And lastly, it is our fault in the industry as a whole, not to promote the advanced certifications like we should. (I should explain here that I am in no way saying that uncertified or unlicensed opticians are not knowledgeable in their field. I do think however that since they know it they should flaunt it:cheers:)

I would even go so far as to say that most tests for certification should include a good deal of hands-on work under observation.

I like the idea of hand-on work on certification exams. I think that the FCLSA mode of examination(where you have a practicle exam in front of 12? members of the board of the CLSA) is a format that could, and probably should, be duplicated on the master level for the ABO. I don't think however, that it would be realistic for the ABOC. Remember, that exam only tests basic knowledge. And as for the ABO-AC, that is a VERY hard test IMHO, even if it is multiple choice. The failure rate, even with the appropriate study material, is in the 90th percentile. Not good odds

Again, MHO FWIW :shiner::shiner::):)

[quality.914]

the oblique meridian formula is (sph. power + cyl. power)sin theta, (which is the axis) squared.
so in your example: +4.00 + -1.00sin 60 squared which is the difference between the given axis and the axis intended which is 90 degrees.
or you can remember the magic column that our fellow member supplied in his reply. Good luck I took mine 3 years ago. I studied from the optical formula tutorial, ophthalmic dispensing by brooks and borish, and the exam review. Sin the angle first then square it then multiply by the cyl. then add the sph.

[Debbylariv]

I just joined this group and I'm taking my test on the 20th of August...for some reason I cant remember formulas...I have the book on Optical formulas. What ever help you can give me with this would be great...I the answer I got on the vertex problem above is 8 and on the near vision...-5.00 -1.00 x 180/-4.75 -1.25x175...

[MakeOptics]

I have a method that I teach to test takers that is fast and intuitive but gets me flack with opticians. Keep in mind it is a shortcut.

USE THE DIFFERENCE IN AXIS AS A PERCENTAGE (that's it)

Examples from this thread:

What prismatic effect would a patient experience looking 4mm below the optical center of a pair of +4.00 -1.00 x 030 lenses?


a) 1.30 diopters of prism B. U.
b) 1.30 diopters of prism B. D.
c) 1.60 diopters of prism B. U.
d) 1.60 diopters of prism B. D.

Difference in axis
90 - 30 = 60

Cylinder Effect
-1.00 x 0.60 = -0.60

Total Power at Meridian
4.00 + -0.60 = 3.40

Prism
3.40 x 4 / 10 = 1.36 BU

Closest answer = a


What prismatic effect would a patient experience looking 5mm above the optical center of a pair of -5.00 -2.00 x 150 lenses?


a) 2.50 diopters of prism B. U.
b) 2.50 diopters of prism B. D.
c) 3.25 diopters of prism B. U.
d) 3.25 diopters of prism B. D.

Difference in axis
150 - 90 = 60

Cylinder Effect
-2.00 x 0.60 = -1.2

Total Power at Meridian
-5.00 + -1.2 = -6.2

Prism
-6.2 x -5 / 10 = 3.1 BU
(notice I used a sign for the optical center position, the optical center is 5mm below the patient's line of sight, so it's negative. By carrying a sign convention into your problems; figuring out IN, OUT, UP, and DOWN is trivial since a negative is either DOWN or OUT and a positive is IN or UP which is more intuitive when working on cartesian planes)

Closest answer = c

Very few cases exist where this trick won't work on a test, in real life, you would measure in a lensometer so the formula is only for theory.

[Debbylariv]

Thanks so much for that shortcut, do you have one for Vertex distance that will help me to remember and any other formula you can give me.....

[MakeOptics]

The formula for effective vertex power is:

F = Power
x = change in vertex

Feffect = F / (1 + x * F)

Let's take an example from the thread and work it out, then I will show you a shortcut!

What is the effective power of a pair of -9.00 D lenses prescribed at a refracted vertex distance of 21mm if the lenses are worn at a vertex of 8mm?

F = -9.00
x = 21 - 8 = 13mm = 0.013m (who fits like this, lol)

Feffect = F / (1 + x * F)
Feffect = -9.00 / (1 + 0.013 * -9.00)
Feffect = -10.19 (you can work the math out but we're not here for a match lesson)

Ok, now the good stuff the shortcut:

First lets rework the problem:

Feffect = F / (1 + x * F)

F = 1/f (focal length formula, simple to remember and need for the test anyway)

rearranged:

f = 1/F

Let's work the focal length into our problem:

Feffect = (1/f) / (1 + x * (1/f))

Now this is the same as:

Feffect = 1/f * 1/(1 + x * (1/f))

So let's just focus on the denominators and simplify them:

denominator = f * (1 + x * (1/f))
multiply the f by 1 first = f
multiply the f by x * (1/f) = x (f * 1/f, cancels out to 1)

Let's rewrite our denominator: f + x

Now let's work on the numerator: 1 * 1 = 1 (done)

Now let's put them together:

Feffect = 1 / (f + x) (I know it can't be that easy, I can't tell you how many times I have opticians question this form of the formula, so we did an example in the beginning let's work it out with our new and improved formula)

F = -9.00
x = 21 - 8 = 13mm = 0.013m

f = 1 / F
Feffect = 1 / (f + x)

f = 1/-9.00 = -0.1111
Feffect = 1 / (-0.1111 + 0.013)
Feffect = 1 / -0.0981
Feffect = -10.19

Wow same answer whadya know, for compensated power you would just swicth the sign

Fcomp = 1 / (f - x)

[wmcdonald]

I am a person that can probably pass a multiple choice test on anything with no preparation. Having said this I am not at all sure that without preparation I could pass a basic optical test without some review.

I do not think think multiple choice tests should be used for certification in anything as I am sure there are many like me that can find the most logical answer given four choices to most things.

I would even go so far as to say that most tests for certification should include a good deal of hands-on work under observation.

Comments anyone?

Chip

Chip,
Psychometric evaluation now allows for a fairly consistent review of the knowledge of those taking the tests. It can be as hard, or easy, as the testing folks want it to me. Physicians, Nurses, etc, all use computerized tests today. But they all add a hands-on component that is completed at their college or university. 2/3 of those studying to become Opticians are apprentices, and research clearly indicates there is little actual training going on.......they have to read and learn it themselves. Until we revise this outdated, and worthless form of cheap labor we call training we can probably do no better. Formal education is what is needed. The alternative to psychometric evaluation is a bunch of high school educated "board members" who have no idea what a test questions should look like evaluating those taking the test. In NC, the vast majority of the board members (not all, but the majority) could not pass their own exam, and really need to be out of the testing business completely like most other states. So the ABO/NCLE is it for now. One state now uses the advanced certification exam for state licensure. With an average pass rate of 20%, that crowd is serious about assuring their folks have the requisite knowledge to serve the public, and also have some practical portion. Can these kinds of evaluation measure knowledge.......yes. Adding a practical would be a good thing, and even that can now be done online. Times are changing.

[MakeOptics]

Thanks so much for that shortcut, do you have one for Vertex distance that will help me to remember and any other formula you can give me.....

Tell me the formula's you are struggling with and we'll break them back to basics and build them up in a more intuitive way. Over the years worker bees have been looking for the most compact single use formula for reference. The better method is to use simple formulas and learn how to chain them together (baby steps). That's the reasoning behind the above vertex formula's using the focal length formula first simplifies the equation considerably, the idea is to work in units to make the problem intuitive. An explanation of the above vertex problem will illustrate that:

The focal length of the lens is fixed, so if you move lens by x what's the resultant power, translates to "If I change the vertex what's the effective power"

f = 1 / F
Feffect = 1 / (f + x)

Further explanation why we shouldn't use the traditional form of the equation: "You can't add distance to power, the units are incongruent, you can add distance to focal length because the units are congruent".

[Debbylariv]

Do we really use this stuff in the real world today? Everything is computerized...I have to head to work right now but I will get back to you soon with more questions. Thanks for all you help explaining this stuff. the other questions are with refractive power formula and Sagittal depth and lens thickness. Do you have a shortcut to remembering the cancelling and compounding situation on Prisms? And I think I have most problems with Slab-off ...Better yet can I have you transfer your brain power to mine so I can pass the test!!! :)))

[Debbylariv]

Do you think you could give me another problem I could work out? This way I can try the formula and see if I get the right answer. Thanks :)

[MFC]

First let me say, I have been retired from any active involvement in opticianry five years now.

Having served as Chair of NCLE and President of ABO-NCLE I know a "little" about the exam process. First and foremost, as you suggest Dr., the psychometric validation process requires thorough evaluation of EVERY question on the exams. It is a hair pulling process, to say the least, and takes hours and hours of time to create a defensable exam. Subject matter experts(usually advance certified practitioners and educators) along with a few new certificants gather with those paychometricians to review questions and create new ones. Any question that is to hard, failed by to many examinees, is thrown out as well as any question passed by to many. I usually laughed, to avoid crying, every time I met with the psychometric reps. Those folks are from another planet!

Every effort is made to offer basic exams that measure the minimum requirements for one to be certified as an optician. I am not trying to be defensive here, I am saying that many of our colleagues work very hard to fulfill the needs. Exams are reviewed and updated constately in an effort to meet the expectations of the industry. Additionally, the practical exams are now offered online as well. In a perfect world in-person practicals would be great but over the years it has proven to be difficult, expensive and inconvenient for all concerned.

Computer based testing has and will continue to provide the most accesible and up to date method of standardization.

Best regards,

[Debbylariv]

Thanks for that information. I am trying really hard to study the formulas but just reading the books and trying to figure them out on my own is kind of hard. I do so much better with videos and or someone just showing me. The part I am having difficulties with right now is the image jump and vertical imbalance and Bicentric grinding or slab off.