Use the Prism Compensation Device on the instrument. Put it in the meridian you’re looking for and dial in the number of prism you need. Then center the glasses like normal. (Very simplified explanation.) For example, if you need to verify 10^BU. Then you’ll orient the PCD in the 90 meridian and dial in 10^ BD. Turning it so the power lines move down, then look at the numbers on the dial until you get to 10^. Ideally, if the lens has 10^BU it will cancel the 10^BD you dialed in and powerli es should center at target center. Any variation means you have some undesirable difference. Note, you still need to follow other power rules to ensure strongest lens is centered first and any undesired effect is measured in the weaker lens (2nd lens).
Hi. 2 Question: your lensometer has 4 boack rings but ours at work only has 3 circles. If we get our prism crossing on our very first ring, is that a 1 Diopter? Or half? And second question: in a progressive lens, do we read the prism through the progressives optical cross like we would normally read the distance power? Or do we check it by looking through the optical prism dot on the lens? Also, thanks so much for such helpful video🥰
Q1 - I believe so but the rings should be marked (similar to the target in this video). [Here's an example image that has 1^ as the first ring. www.reichert.com/products/ml1 --> this one uses the inner hash lines to determine where the 0.75, 0.50, and 0.25 are on the target. The ABO Practical simulation "Tutorial and Practice Exam Question Area" discusses how the central target is broken down on slide 24. www.abo-ncle.org/ABO/Exam_Information/Practical_Exams/Practical_Exam_Tutorial/ABO/Practical_Exam/Practical_Exam_Tutorial.aspx?hkey=b53962d8-5427-4cf4-9cd7-2074c6c91d9c] Q2 - Prism is measured/checked at the prism reference point (dot below the fitting cross). Distance power is measured/checked at the distance reference point (circle above the fitting cross). The fitting cross is used only to measured placement in the frame (measuring/checking that the fitting cross corresponds to the wearer's monocular PD and fitting height). This is a good reference that has some good info and pictures at the end that show how the lens should be centered to verify the various aspects of a progressive. aamerniazi.blogspot.com/2014/01/measurement-and-dispensing-of.html. Hope I answered all your questions! Let me know if you need clarification on anything or if you have any new questions.
If you have trouble accessing the "ABO NCLE Tutorial and Practice Exam Questions Area" it can be found on the ABO-NCLE website under Exam Information. Select Practical Exams, then Practical Exam Tutorial. The link is in the text shown on the page. Once opened, select "Mastering Lens Meter Simulation" and go to slide 24 for the measurements of the inner 1^ ring. (ABO-NCLE website www.abo-ncle.org/ABO/Home/ABO/Default.aspx).
@@MsTracyBennett wow! Bless your soul for being such a helpful person! Wish we had more of you in this world🙏🙏🙏 Im now clear about question 2 and thanks again, but even after checking out your link, Im still confused about our lensometer only having 3 rings (and no labels or numbers on them). If prism is showing on first circle (first inner circle), is this a 1 Diopter then?
@@libra8194 Do you know what kind of lensmeter you have? The brand or style. That might help me provide better direction. You can also examine the distance between the circles that you do have, and examine the distance from the center of the target to the first ring. If the ring distance is the same as the distance from the center to the first ring, then the first ring is 1^. If the distance from the center to the first ring is half of the ring distance, then the first ring is 0.5^. I would be willing to bet that first ring on yours is 1^.
@@MsTracyBennett you are 100% right! It is a 1 prism (the first ring) these spaces are all the same, between 1,2 & 3 and also from centre to first ring. Many many thanks to you!! God bless ❤️❤️❤️⭐️⭐️⭐️
The exact same way, except it’s the point where the spher and cylinder cross. You need to toggle back and forth between the two powers until they both align with the point you need to place it or read it from.
@@anweshamaitra3130 you still orient the axis and get power in focus, you just move the center power cross point (the base of the prism) to the point needed to position the prism desired.
Hi Tracy Elise, at first, thank you very mucy your helpful video about "prism in the lensmeter", I have a request, is it possible to share the PDF of the "prism in the lensmeter""?
I’m not sure I know what you’re asking for. I don’t have a PDF version of the lecture. My students have online content and worksheets in the course they have. This lecture was based on that content.
❤love this, thanks to u😊from saskatchewan 😊god bless
Thanks a lot, from Florida! Thanks very helpful
Thank you. This was very helpful!!
Thank you
You’re welcome. I’m glad you found it helpful.
Thank you. I am learning a lot. I am a candidate for Virginia State Exam.
Best of luck to you! We need more licensed opticians!
Hi Tracy, what is your technique for measuring very large prism? (more than 5 in any direction)
Use the Prism Compensation Device on the instrument. Put it in the meridian you’re looking for and dial in the number of prism you need. Then center the glasses like normal. (Very simplified explanation.) For example, if you need to verify 10^BU. Then you’ll orient the PCD in the 90 meridian and dial in 10^ BD. Turning it so the power lines move down, then look at the numbers on the dial until you get to 10^. Ideally, if the lens has 10^BU it will cancel the 10^BD you dialed in and powerli es should center at target center. Any variation means you have some undesirable difference. Note, you still need to follow other power rules to ensure strongest lens is centered first and any undesired effect is measured in the weaker lens (2nd lens).
Hi. 2 Question: your lensometer has 4 boack rings but ours at work only has 3 circles. If we get our prism crossing on our very first ring, is that a 1 Diopter? Or half?
And second question: in a progressive lens, do we read the prism through the progressives optical cross like we would normally read the distance power? Or do we check it by looking through the optical prism dot on the lens? Also, thanks so much for such helpful video🥰
Q1 - I believe so but the rings should be marked (similar to the target in this video). [Here's an example image that has 1^ as the first ring. www.reichert.com/products/ml1 --> this one uses the inner hash lines to determine where the 0.75, 0.50, and 0.25 are on the target. The ABO Practical simulation "Tutorial and Practice Exam Question Area" discusses how the central target is broken down on slide 24. www.abo-ncle.org/ABO/Exam_Information/Practical_Exams/Practical_Exam_Tutorial/ABO/Practical_Exam/Practical_Exam_Tutorial.aspx?hkey=b53962d8-5427-4cf4-9cd7-2074c6c91d9c]
Q2 - Prism is measured/checked at the prism reference point (dot below the fitting cross). Distance power is measured/checked at the distance reference point (circle above the fitting cross). The fitting cross is used only to measured placement in the frame (measuring/checking that the fitting cross corresponds to the wearer's monocular PD and fitting height). This is a good reference that has some good info and pictures at the end that show how the lens should be centered to verify the various aspects of a progressive. aamerniazi.blogspot.com/2014/01/measurement-and-dispensing-of.html.
Hope I answered all your questions! Let me know if you need clarification on anything or if you have any new questions.
If you have trouble accessing the "ABO NCLE Tutorial and Practice Exam Questions Area" it can be found on the ABO-NCLE website under Exam Information. Select Practical Exams, then Practical Exam Tutorial. The link is in the text shown on the page. Once opened, select "Mastering Lens Meter Simulation" and go to slide 24 for the measurements of the inner 1^ ring. (ABO-NCLE website www.abo-ncle.org/ABO/Home/ABO/Default.aspx).
@@MsTracyBennett wow! Bless your soul for being such a helpful person! Wish we had more of you in this world🙏🙏🙏 Im now clear about question 2 and thanks again, but even after checking out your link, Im still confused about our lensometer only having 3 rings (and no labels or numbers on them). If prism is showing on first circle (first inner circle), is this a 1 Diopter then?
@@libra8194 Do you know what kind of lensmeter you have? The brand or style. That might help me provide better direction. You can also examine the distance between the circles that you do have, and examine the distance from the center of the target to the first ring. If the ring distance is the same as the distance from the center to the first ring, then the first ring is 1^. If the distance from the center to the first ring is half of the ring distance, then the first ring is 0.5^. I would be willing to bet that first ring on yours is 1^.
@@MsTracyBennett you are 100% right! It is a 1 prism (the first ring) these spaces are all the same, between 1,2 & 3 and also from centre to first ring. Many many thanks to you!! God bless ❤️❤️❤️⭐️⭐️⭐️
How do we measure a prism that is superimposed on a spherocylindrical lens instead of just a spherical lens?
The exact same way, except it’s the point where the spher and cylinder cross. You need to toggle back and forth between the two powers until they both align with the point you need to place it or read it from.
Wont the centre point of the grid be blurred in case of a spherocylindrical lens?
@@anweshamaitra3130 you still orient the axis and get power in focus, you just move the center power cross point (the base of the prism) to the point needed to position the prism desired.
Hi Tracy Elise, at first, thank you very mucy your helpful video about "prism in the lensmeter", I have a request, is it possible to share the PDF of the "prism in the lensmeter""?
I’m not sure I know what you’re asking for. I don’t have a PDF version of the lecture. My students have online content and worksheets in the course they have. This lecture was based on that content.
thank you for your response @@MsTracyBennett
@@hanifidemir8075 you’re welcome. Sorry I couldn’t be more helpful.