Maybe someone else can explain this..

[Jeff Trail]

Guys,

Ever have one of those days? .. I got an order for an RX from one of my accounts and on the RX slip the OD wants 2^ at 115 AND 3^ BO ...the RX is a PL-.50x90 (OU) .. I called the account first and told her you can't get those numbers ..of course she does the usual "why?" ..I explain to her if she ask for 2^ at 115 it would break down to 3/4 out and 2^ up.. but if you want 2^ at 115 you can't have 3 BO :rolleyes: the only way if you wanted to make sure you had to get 3 BO and still have it at the 115 then you have to increase the amount of UP prism along the 115 OR change the axis of the prism ... We ended up on a three way conference call with the account and the OD and myself and I even had to draw it out on graph paper to get them to understand what I was saying... NOW is it me or do they not teach prism any longer? :) I still don't think they understood what I was saying about the amount and the direction and the numbers they "wanted" and how it did not ADD UP.. Anyone think of an easy way to explain how prism works ? Not the the "effect" of prism but how you request it and how it plots out.. I'm really flustered on this one, both the OD and the optician got confused from the point of talking about compound prism, resultant prism and the difference between that and trying to mix prism requested in an axis form and a direction form all in one eye ..YIKES..I have the flu and do NOT feel like trying to explain something I KNOW is not possible and both of them telling me "well I called this other lab and they said they could do it"..what B.S. of course they said they can "do it" they want the account..sheesh, BUT you still can not get 2^ at 115 and then expect to be able to bring it down with a compensating ring and have it fall at 3 BO THAT IS MATHMATICALLY IMPOSSIBLE..unless we happen to try to do this near a black hole and can "warp" light :)
The way I left it they can give me the amount of total prism she (the OD) wanted at any axis.. or she could write it in compond form either way is easy enough to do BUT you can't mix the two and expect the numbers she wanted...
One I'm need to retire, or we need to boost the education level somewhere or I need a flu shot!! :)
Any idea's on what you 1) thinks she wants? 2) an easy way to explain how apples and oranges can't be mixed 3)Want to buy my lab :)

Jeff "cranky,coughing and sneezing" Trail

[shanbaum]

Well, the OD might have just inserted a 2 diopter prism in a trial frame, oriented at 115, along with a 3 diopter prism oriented laterally, and wanted you to combine them.

Or, maybe she's clueless, as you suggest.

[Jeff Trail]

Robert,

Tried that (thinking along the same lines as you were) ..now if I plotted out 2 at 115 and punched in 3^ BO into the equation the combination would end up giving me 4.45^ at 155 (resultant) ...and she said NO I want 2 at 115 and 3^BO :rolleyes:.. I also ran it as a compound and it more or less gave me the same amount of resultant prism (4.5^) at 148 though (2^BU/3BO)...
I just can't figure out exactly what they are doing or wanting and I tried doing it every combination I know of.. maybe some of you guys know something about prism I am missing :) I know mathmatically and physically I can NOT grind a lens and when you look in a lensometer at the target it is going to be 2^ at 115 and if you turn the compensating ring down it will end up at 3 ^BO.. any others want to try to jump in? .. Maybe from an OD's point of view?

Jeff "where is my 12hr.contacts,niqual and tissues" Trail

[chip anderson]

Look for many years I had a friend who was gruff old man who was probably the best ocular muscle surgeon in the country (at least he seldom if ever needed to go back and do same twice and the eyes stayed straight until the patient died). Many times I had him pull me aside and say: "I am not a prism man, can't you do this with de-centration." This from a man that was educated way back there, before surgical bucks out~weighed patient need.

I also worked for a man who had been in the optical business since the 1920's and told me that one of the well reputed ophthalmologist, he knew attended a lecture with him. He overheard the doctor tell the speaker that he was very impressed with his speech, but what was the term he kept using, Diopter?

Chip(Ours is not to reason why) Anderson

[This message has been edited by chip anderson (edited 04-08-2001).]

[Darryl Meister]

Hi Jeff,

As usual, I'm going to go with Robert on this one... I suspect that they simply dropped both prisms in and now need the net result.

The 2 PD @ 115 breaks down to 0.85 PD out and 1.81 PD up. Adding this to the 3.00 PD out, and you have 3.85 PD out and 1.81 PD up.

It sounds like there is no easy answer for you here, since apparently neither the OD nor the optician understands the matter enough to comprehend what needs to be done. Or perhaps there is a communication issue between you.

I would reiterate to them that when the two independent prisms they are requesting are added together they combine to produce a resultant prismatic effect. Tell them that you will provide the job with the two prisms, as requested, but they should expect to neutralize the job with 3.85 PD out and 1.81 PD up.

Best regards,
Darryl

[Corey Nicholls]

Try emailing David Wilson. He is our optics guru here in Oz and also a moderator here for the International Optics Forum. Try him at-
david.wilson@tafensw.edu.au
He might steer you in the right direction.

Corey.

[Sara]

R is 2^@115,L is 3^@0,can this mean each eye is independant in its binocular anomalies,i.e.right eye requires 2^up&out@115 for cyclophoria,and left eye requires 3^for whatever exo/eso.I am poor at prisms but was just thinking if it is this way.
Thanks,
Sara

[Darryl Meister]

Originally posted by Sara:
R is 2^@115,L is 3^@0,can this mean each eye is independant in its binocular anomalies,i.e.right eye requires 2^up&out@115 for cyclophoria,and left eye requires 3^for whatever exo/eso.

Hi Sara,

That is a good observation; it is entirely possible that it was done with each eye independently. However, either way the lens would have to be made with 3.85 PD out and 1.81 PD up if it is done in only the right lens -- as the doctor has requested. If the prism is split between the two eyes, it would probably make more sense to split them evenly to maximize the optics and cosmetics of the job -- unless there is a non-concomitant strabismus or something.

Best regards,
Darryl

[Sara]

Hi Darryl,
You are right that's how it should be.I think confusion arises because optometrist use rotary prisms during refraction mounted on phoropter head and jot down readings directly on Rx pad without thinking of spectacle fabricator understanding.
Thanks,
Sara

Mr.Jeff Trail,
You fabricate what you think is correct according to best of your knowledge.I hope you won't go wrong.

[This message has been edited by Sara (edited 04-09-2001).]

[Darryl Meister]

Hi Sara,

In any event, everyone's post adds a little more perspective and clarity on these issues! ;)

Best regards,
Darryl