Intermediate formula question

[CatwithGlasses]

Hello everyone! In studying for the ABO exam I came across a question and I have no idea how to arrive at the answer.

"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"

I know the answer is -0.50 but I have no idea how to arrive at that answer. I am comfortable using the lensometer to find sphere, cylinder and reading power, and I would think knowing that I could find the intermediate (usually half the add) but I am thrown by this particular question.

Any help would be much appreciated. Thanks!

[newguyaroundhere]

Hello everyone! In studying for the ABO exam I came across a question and I have no idea how to arrive at the answer.

"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"

I know the answer is -0.50 but I have no idea how to arrive at that answer. I am comfortable using the lensometer to find sphere, cylinder and reading power, and I would think knowing that I could find the intermediate (usually half the add) but I am thrown by this particular question.

Any help would be much appreciated. Thanks!

Re-read the question again and you will see how to calculate your answer.

[Robert_S]

Lol

[Robert Martellaro]

Hello everyone! In studying for the ABO exam I came across a question and I have no idea how to arrive at the answer.

"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"

I know the answer is -0.50 but I have no idea how to arrive at that answer. I am comfortable using the lensometer to find sphere, cylinder and reading power, and I would think knowing that I could find the intermediate (usually half the add) but I am thrown by this particular question.

Any help would be much appreciated. Thanks!

Welcome to OB.

Hint: Add powers always use "plus" values.

Hint: The prescribed add power in the above example is +2.50 D, the difference in power between the distance power and the near power.

http://www.themathpage.com/alg/add-s...ed-numbers.htm

[Dr. Bill Stacy]

But it's a trick question and did NOT ask for the "prescribed" intermediate. A really badly written question that should be thrown out. Having said that, the question asks for the "actual" power which means to me that power read by lensometer itself, through the intermediate, which would be +.50

[Uilleann]

This is a classic ABO level question. Written to be as deceptive and tricky as possible. Nothing but word salad.

Anyway, as I read it (it seems there is a prescribed power of +0.50 for the intermediate, but the full add was written as +1.50...which means the intermediate would more commonly be split to a +0.75 yes?)

SRx: -1.00 Sph
Add: +1.50
Intermediate Add: +0.50 (which would normally just be half of the full add or +0.75 instead of +0.50...but whatevs)

If the above was in the real world (somewhere the idiots writing the ABO exams seem to avoid at all costs!) the sphere would become -0.25 in the intermediate, using half the full add.

Regardless, who are these monkeys banging away at keyboards putting this tripe together and calling it a realistic examination to demonstrate competency based in any form of ophthalmic dispensing reality???

[Dr. Bill Stacy]

As a former chariman of the Examination for Licensure Committee of the Calif. State Board of Optometry, I was responsible for questions on the written exam we used to give (until Calif went totally NBEO) as well as developing the Clinical exam part of that exam. I had help from the Central Testing Unit of the Calif Dept. of Consumer Affairs and one of the hardest tasks was to develop NON TRICK questions, and questions that actually applied to practicing optometry. We also did post exam reviews question by question and "threw out" any that were missed by more than a certain % of test takers, around 30% as I recall. Then all the tests were rescored using the remaining questions. This process often helped some and hurt others (the ones that answered the bad question correctly). But it was a truly scientific construct.

If the writers of the optician testing develop bad questions like the one above and do not toss them out, they are running a bad thing and someone needs to clean it up. And no, the above question did not say "prescribed" anywhere, only commas separating the various "lensometer readings" from one another, so I believe my answer of +.50 is the correct "actual power", whatever that means. Incidentally, occasionally we would find that the keyed answers were in error, which we would find when a large number, say 50% picked a particular "wrong answer". Test question writers are not always correct. In those cases we would correct OUR error, put the question back in, and recompile the test scores one more time. The only downside of this process was that we gave tests in June and often did not report results until September.

[Robert Martellaro]

This is a classic ABO level question. Written to be as deceptive and tricky as possible. Nothing but word salad.

Anyway, as I read it (it seems there is a prescribed power of +0.50 for the intermediate, but the full add was written as +1.50...which means the intermediate would more commonly be split to a +0.75 yes?)

No.

using this lensometer reading: OD -1.00, Add +1.50, intermediate +0.50?

We can determine the Rx for the distance, intermediate, and near using this information.

But it's a trick question and did NOT ask for the "prescribed" intermediate.

But it does ask for the Rx.

"What is the actual intermediate power of the Rx..."

If lensometry shows a distance power of -1.00, and an intermediate power of +.50, the intermediate (Rx Add) power has only one correct value. Not a trick question.

[MakeOptics]

Hello everyone! In studying for the ABO exam I came across a question and I have no idea how to arrive at the answer.

"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"

I know the answer is -0.50 but I have no idea how to arrive at that answer. I am comfortable using the lensometer to find sphere, cylinder and reading power, and I would think knowing that I could find the intermediate (usually half the add) but I am thrown by this particular question.

Any help would be much appreciated. Thanks!

-1.00 + (+0.50) = -0.50

I'm sure it could be interpreted to read other ways but that's using the info given.

If I was to calculate using the 40cm* as a working distance:

1/0.4m = 2.50D

Assuming near at 30cm*:

1/0.3m = 3.33D

Accomadative reserve = near focal power - add = 3.33 - 2.50 = 0.83D (oops used 2.50 as the add instead of 1.50 like your answer) 3.33 - 1.50 = 1.83D

2.50D (from intermediate calc 1/0.4m) - 0.83D = 1.67D (I would round down knowing the reserve would help) +1.50 (corrected again from aforementioned error) 2.50 - 1.83 = 0.67D (again I would round down) 0.50D

Total intermediate power = -1.00 + 1.50 = +0.50, this method would allow you to adjust for any working distance. (corrected from above) -1.00 + 0.50 = -0.50D


*(no numbers were hurt in this example, all numbers have had their values changed to protect the innocent)

[Dr. Bill Stacy]

No.

We can determine the Rx for the distance, intermediate, and near using this information.

But it does ask for the Rx.


If lensometry shows a distance power of -1.00, and an intermediate power of +.50, the intermediate (Rx Add) power has only one correct value. Not a trick question.

Then we have a different idea as to what is meant by "actual power" and maybe also of "Rx" Perhaps the writer meant "what is the prescribed add power of the intermediate". That is not what he/she wrote. To me "actual power" means the power as read by a lensometer or other device. And Rx can mean a written prescription or a prescribed lens. This is a great example of a question where the keyed answer is wrong. As wrong as the question itself.

[Robert Martellaro]

Re-read the question again and you will see how to calculate your answer.

Yup, it's more straightforward than it looks.

The Rx is -1.50 add +2.50, with an intermediate add of +1.50. But CatwithGlasses needs to explain why this is correct. Let us know if you need more help.

[Robert Martellaro]

Perhaps the writer meant "what is the prescribed add power of the intermediate". That is not what he/she wrote.

Here it is again.

"What is the actual intermediate power of the Rx...

It seems clear to me that they're asking us to determine the Rx, specifically the add for intermediate, from the lensometry results. Routinely done after surfacing and during final inspection.

[Uilleann]

Upon re-reading, I realize I was skimming too quickly, and misread the lensometry portion. I stand humbly corrected.

[Dr. Bill Stacy]

Here it is again.

It seems clear to me that they're asking us to determine the Rx, specifically the add for intermediate, from the lensometry results. Routinely done after surfacing and during final inspection.

I looked around the internet and couldn't find the term "actual power" except as it relates to lensometry and lens optics, never as referring to the power specified in a written Rx. This is why in my original post I said "whatever that is", because normally we would say vertex power or effective power, not actual power. When referring to written Rx powers, we don't say "actual". We might say prescribed power or written power. The writer of the question used non standard terminology which itself should be prohibited in any test question for any purpose.

[MakeOptics]

Upon re-reading, I realize I was skimming too quickly, and misread the lensometry portion. I stand humbly corrected.

I missed that too, had the writer of the question worked for me they would have hit the bricks a long time ago. I have lost the patients for dealing with poorly or ambiguously worded questions. That's why I gravitate towards math questions it's a universal language.

Distance = -1.00
Intermediate = +0.50
Add = +1.50 <--- problem you cannot read an add in a lensomter, you can read the near power and deduce the add, incorrect use of the term.

Distance = -1.00
Intermediate = +0.50 <--- if the add was +1.50 then the intermediate power reading cannot be +0.50 since that is the power at the near.
Add = +1.50

Either way you interpret the question the writer (of the question not the poster) needs to be more clear.

[uncut]

Hello everyone! In studying for the ABO exam I came across a question and I have no idea how to arrive at the answer.

"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"

I know the answer is -0.50 but I have no idea how to arrive at that answer. I am comfortable using the lensometer to find sphere, cylinder and reading power, and I would think knowing that I could find the intermediate (usually half the add) but I am thrown by this particular question.

Any help would be much appreciated. Thanks!

OP...doncha just love questions designed with a twitter, or text mentality?

My interpretation of the question: Assuming you have posted the complete information about the question, if not,

please provide.

I assume the lensometry is of a trifocal? I assume the lensometry refers to the actual "readout" of the device, so minus one makes one assume that the distance power recorded is -1.00, the add reading is at +1.50, which gives us a mental "prescribed" (or RX add of )+2.50.

If the lensometry reading is +0.50, in the intermediate area of the lens, the intermediate is +1.00, provided by the lens fabricator, deliberately(Rx'd)..... or in error.

Your answer was given, by you, to be -0.50, is either in error, or the question is in error, and therefore I would understand why you would be puzzled by this. I am, too!

A interesting 1st post, and welcome to the forum, Cat withGlasses!

[Dr. Bill Stacy]

"What is the actual intermediate power of the Rx using this lensomerter reading: OD -1.00, Add +1.50, intermediate +0.50?"

!

I would have written the question like this: "What was the prescribed Add for the intermediate seg of a lens that measures on a lensometer this: -1.00 in the distance region, +1.50 in the near seg , and +0.50 in the intermediate seg?"

But then the answer would have been +1.50, not the -.50 that was apparently the key answer? Are you sure of the exact wording of the question and the key you gave (you said you were sure)? If so then it's worse than I thought.

[Diane]

The OP stated that this is a study question. Some here are responding as though this is a question on the exam itself. May I remind each that the test is a multiple choice test. While this may be an interesting scenario, it is only an example. What is being studied?

Diane

[Dr. Bill Stacy]

Someone described it as a "classic abo test question"

[Robert Martellaro]

Add = +1.50 <--- problem you cannot read an add in a lensomter, you can read the near power and deduce the add, incorrect use of the term.

Yup. But the question used the term "lensometer reading". It's as clear as mud.

[Uilleann]

Again - nothing but word salad.

A classic ABO move, designed not to test ophthalmic dispensing competency - but to test 'test-taking ability'. They've built an entire empire around it.

[Uncle Fester]

OP...doncha just love questions designed with a twitter, or text mentality?

My interpretation of the question: Assuming you have posted the complete information about the question, if not,

please provide.

I assume the lensometry is of a trifocal? I assume the lensometry refers to the actual "readout" of the device, so minus one makes one assume that the distance power recorded is -1.00, the add reading is at +1.50, which gives us a mental "prescribed" (or RX add of )+2.50.

If the lensometry reading is +0.50, in the intermediate area of the lens, the intermediate is +1.00, provided by the lens fabricator, deliberately(Rx'd)..... or in error.

Your answer was given, by you, to be -0.50, is either in error, or the question is in error, and therefore I would understand why you would be puzzled by this. I am, too!

A interesting 1st post, and welcome to the forum, Cat withGlasses!

This was my thinking as well. But boy, the question really should be phrased better.

And another welcome to Catw/glasses!!!

[smallworld]

Reminds me of a tricky ABO question , A man comes into the optical after cataract surgery and is wearing a lined bifocal. He wants to order post cataract surgery glasses. The optician quickly determines this patient is wearing his wife's glasses. The patient is informed he's wearing his wife's glasses, to which he gets very angry and says "How do you know?". The patient makes the optician get out his file and look through the records, which showed the patient has always worn progressive bifocals. How did the optician know the glasses were the patient's wife's?

[uncut]

Reminds me of a tricky ABO question , A man comes into the optical after cataract surgery and is wearing a lined bifocal. He wants to order post cataract surgery glasses. The optician quickly determines this patient is wearing his wife's glasses. The patient is informed he's wearing his wife's glasses, to which he gets very angry and says "How do you know?". The patient makes the optician get out his file and look through the records, which showed the patient has always worn progressive bifocals. How did the optician know the glasses were the patient's wife's?

Multiple choice:

A: Optician's radar.
B: Women's intuition.
C: By violation of the privacy act.
D: All of the above.

[smallworld]

They were gold cat eye rimless.