Pro tip
Read prism @ PRP, not MRP. Don’t argue with me. IATA!
Oh, you just passed the ABO? Gotcha. You also sold a PAL @ 11mm FH. So…….ya.
grrrrrrrrrrrr
Pro tip
Read prism @ PRP, not MRP. Don’t argue with me. IATA!
Oh, you just passed the ABO? Gotcha. You also sold a PAL @ 11mm FH. So…….ya.
grrrrrrrrrrrr
I bend light. That is what I do.
That 11 seg was almost certainly because some marketing department SAID SO. Also, they only work if you put that DANGEROUS BLUE LIGHT yellow filter and purple shiny mirror on too.Originally Posted by lensmanmd
:D
I once had a doctor tell me how it was literally impossible to measure prism in PALs. They were then dumbfounded when I explained it was explicitly called a prism reference point and that's how you did it
That just shows that anyone can get a degree or a title...I once had a doctor tell me how it was literally impossible to measure prism in PALs. They were then dumbfounded when I explained it was explicitly called a prism reference point and that's how you did it
I was on the advisory board of one of the major Optometry schools at my last meeting when I resigned they decided that teaching lens design was no longer necessary as Optometry was become more medical than lens oriented.
Maybe this is a stupid question, but I don't claim to be a smart person
I most definitely understand to look at the prp for prism, and I understand that there is a prp because of prism thinning. What I don't get is why the customer isn't seeing the prism when they look through the distance portion of their glasses?
For example, I check in a pair of glasses on a manual lensometer and see a diopter vertical difference between the lenses in the distance, but nothing at the PRP. Why isn't the customer seeing that vertical imbalance when they look through the distance? I'm sure the answer has to do with prism thinning but I still cannot get over the idea that I can see the imbalance in the lensometer in the distance but they don't.
Last edited by NAICITPO; 07-09-2022 at 03:03 PM.
The patient is looking thru the imbalance you see in the lensometer it is just not causing a problem for them. If there is no imbalance at the prp and their is imbalance in the distance that is due to a difference in Rx between the right and left lens. They would have the same problem at the reading level which is the reason a slab off is prescribed. If you want no imbalance in the distance this can be done but it will increase the imbalance at near. Most people can handle 1.5 diop of imbalance without seeing double hence the prp is in between the distance reference position and the near reference position to minimize the imbalance at both positions.
Most patients can accommodate up to 2.5 vertical.
My post was about the ability to properly read the prism. This was exasperated by prescribed prism. 2.5 up/2.5 dn. In a PAL. Total prism was 4.87. Prescribed was 5.
OD was 2.67 up. OS was 2.12 dn. 4.87 total +/-. RX was W/I ANSI OU. The optician did not
1. Understand PRP. 2. Did not understand ANSI. 3. Should not have sold a PAL for this.
Same optician sold a PAL @11mm SH. 11mm. In. A. PAL.
Enough said.
I bend light. That is what I do.
It's hard to find a frame that generates an 11 PRP. Maybe a half eye?
I would say most everyone can tolerate a 1^ vertical, but 2^ is pushing it. But there's a distinction between something that has been gradually accumulating over years (like a gradually developing aniso) vs. a sudden change, say, from a cataract...big problemo.
Another interesting phenomenon is that some of these higher vertical imbalance people begin to suppress the foveal vision in order to "remove the stress" of maintaining bifoveal fixation. They just have reduced depth perception.
One of the things that wowed me when talking to good ol' Peter Shaw of Shaw Lens/Cherry Optical fame is that they calculate prism compensation (and maybe others do as well) in a more sophisticated way than cave-man Prentice's Rule and managing some of the prismatic imbalance their way can improve binocular performance. (Heck, they used to ask you to see how much vertical prism the patient could tolerate--to your all's point--as a parameter before making the lenses.) I'm impressed. Just bring your wallet. But it's worth it when you need it.
Last edited by drk; 07-11-2022 at 12:13 PM.
Lensman (Maryland): you need to get to the beach before you go "optical" on someone. HAHAHAHA
Day drinking also helps, I hear anyway...
I just got back from Ann Maria Island... it did not help and I'm ready to go "optical" on people. Take NAICITPO's advise and start the the day drinking.
On a side note... it is hard to believe how may opticians have no idea about the PRP. It boggles the mind. I worked with an ABO certified optician and she was one of the most clueless people I've ever met. How ever did she pass??? Good guesses? Idk. She may have passed with the lowest score and maybe those guesses helped her to pass. I remember taking the test and a girl waiting with me to go in told me it was her 4th attempt to pass. Eeek.
Update
I received a “love letter” from the optician. Pt can’t see out of OD. Prism is 3.5 up. No other details. The only spot that is 3.5 up is at the distance, not the MRP. Not the PRP.
Reviewing all orders, OD was originally +.50, no prism. Now, -.75, 2.5 BU. I’m remaking it now, but there will be an RX change in the future. But sure, it’s the prism. McTicians…….sigh.
I suggest ABO to raise passing to at least 80% from 70%.
I bend light. That is what I do.
Go Optical. C'mon. Do it...
I’m struggling to suppress my inner Roy Kent.
I bend light. That is what I do.
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
Bookmarks