As always this is a great explanation, I have been spent a lot of time looking for this formula. I am interested in a plano lens (no magnification) with radius of curvature of 1300mm. That is both sides are curved with r=1.3m and uniform thickness. Can you make such a lens?
Hello, I am wondering if it is possible to generate and polish an Rx range from -12 to a +15 all on a plano base sf lens? In glass? If so what is required?
You would need to call the lab on that one 800-525-1274 they are in Iowa on CST. We handle glass and specialty work but a project like that would take some planning and some money. John
You can't. You can measure them with a lens clock and get close. You can't use a formula to determine them. I know, I know - I can't get my head around it either. The radius - power stuff only works with plano backsides. You can't keep running with it for full lens power(s).
These examples are different from toric transposition examples. This formula works off a plano back curve. [I struggle with that too.] You can't use this to calculate total power with anything but 0.00 as the back curve. Toric would indicate back curves other than plano so you would be working toric transposition and then converting power to curvature that way. Contact lenses work differently and they have charts for converting curves to power. "K" readings are curve readings which are then converted to powers. I'm a bit rusty on that stuff - maybe someone else can help both of us.
My eyeglass power is -2.75 cyl. and the axis is 165 degree. The axis has changed recently from 160 degrees to 165 but after wearing new eyeglass I’m feeling little nauseas. Is it normal?
0.00 -2.75 X 160 to 0.00 - 2.75 X 165 could actually create a problem. Tolerance for -2.75 is only 2 degrees. BUT - if during refraction you felt that 165 was better than 160 that may be why it was moved. Cylinder position usually doesn't change more than a degree or two if at all. I'd ask them to check EVERYTHING on the glasses and then ask them to move you back to the 160 you like.
But that is not how a lens in a spectacle looks like. Those lenses do not have a flat surface on one side like in your examples. They have two curves with a different radius; the inside radius (the one at the side of the eye) and the outside radius. How are those calculated (to start with, let's keep it to purely spherical lenses; i.e. no cylinder).
LOL You wouldn't believe how I struggled with that same exact concept. In fact it is the reason it is one of the last in the theory series. I too wanted to see it as an "eyeglass lens" where that simply isn't possible. It is why some of us are opticians and some people are engineers and some people really understand physics. Take a deep breath, let it out... move on my friend. I feel for you. John
@@LaramyKOptical Thanks for your answer. I'm not an optician and I'm not an engineer in optics. (I'm an engineer in IT). But, I'm retired now and I just had a new prescription for my glasses and I thought it would be a good idea to try to understand what it was all about so I started to look around on the web and that's how I came to your (excellent) channel. I learned a lot already. But anyway, I would like to get an even better idea on how it all works. From what I could find, I could already deduce that for a negative prescription (negative dioptre) the radius of the inside curve has to be smaller than the radius of the outside curve. For a positive dioptre, it's the inverse. But I haven't found any practical examples up till now (real measures) so I was hoping you could shed some light on it.
@@peterdegelaen I was up at 2 AM this morning thinking about this one. I rarely reply to comments after 7 PM but yours caught my eye. Glad you read it as it was intended. You may find the videos on toric transposition helpful. You may find the How It's Made video helpful. After that, for the hard core stuff you would need a book like Modern Ophthalmic Optics from the folks at IOT. As soon as you add in those second, third or free-form curves on the back you leave the realm of basic math and basic optical theory and enter the realm of some pretty complex physics. Being a bear of little brain that stuff is outside my understanding. Don't tell anyone and it's not like I'd post it on YT or anything but I was more or a less a puppet on that one. The examples actually came from an OD who teaches optics. I didn't credit him because I didn't think he would want his name associated with a video that mocks the "p" word. The rest was vetted by Keith, the K in Laramy-K. He is an all around genius and is a real life actual physicist. Like you I couldn't get past the, "but that isn't an eyeglass lens" part. But the math is solid and the concept is correct and the Surface Power Formula certainly is a part of optics. John PS: The creation of power in a lens is the process of lens surfacing. So surfacing or maybe even generating would be terms to look for.
@@LaramyKOptical OMG! It was never my intention to make you lose sleep because of my questions. Thanks a lot for your extensive answer. Best regards, Peter
The best all the time 👍🏻👍🏻👍🏻
As always this is a great explanation, I have been spent a lot of time looking for this formula. I am interested in a plano lens (no magnification) with radius of curvature of 1300mm. That is both sides are curved with r=1.3m and uniform thickness. Can you make such a lens?
Would need to know a lot more about the project. Email me through the OpticianWorks website.
Hello, I am wondering if it is possible to generate and polish an Rx range from -12 to a +15 all on a plano base sf lens? In glass? If so what is required?
You would need to call the lab on that one 800-525-1274 they are in Iowa on CST. We handle glass and specialty work but a project like that would take some planning and some money. John
What about if I need to find radii of curvature of principal meridians made in toric form with base curve
You can't. You can measure them with a lens clock and get close. You can't use a formula to determine them. I know, I know - I can't get my head around it either. The radius - power stuff only works with plano backsides. You can't keep running with it for full lens power(s).
Amazing thank you. Do you have anything on how to calculate the ROC if it’s a toric lens? 😭
These examples are different from toric transposition examples. This formula works off a plano back curve. [I struggle with that too.] You can't use this to calculate total power with anything but 0.00 as the back curve. Toric would indicate back curves other than plano so you would be working toric transposition and then converting power to curvature that way. Contact lenses work differently and they have charts for converting curves to power. "K" readings are curve readings which are then converted to powers. I'm a bit rusty on that stuff - maybe someone else can help both of us.
@@LaramyKOptical thank you!!! I’m just now learning about toric transposition so maybe that’ll clear things up for me 😭
My eyeglass power is -2.75 cyl. and the axis is 165 degree. The axis has changed recently from 160 degrees to 165 but after wearing new eyeglass I’m feeling little nauseas. Is it normal?
0.00 -2.75 X 160 to 0.00 - 2.75 X 165 could actually create a problem. Tolerance for -2.75 is only 2 degrees. BUT - if during refraction you felt that 165 was better than 160 that may be why it was moved. Cylinder position usually doesn't change more than a degree or two if at all. I'd ask them to check EVERYTHING on the glasses and then ask them to move you back to the 160 you like.
Pls make videos for contact lenses
I'm sorry but I'm not a contact lens person and we can't find anyone to create the content. I wish we could. John
Mantra: The shorter the radius, steeper the curve, higher the power, thicker the lens
Hey - that sounds very, very familiar! I think I said that1 ;-) John
@@LaramyKOptical Yes it's your words
But that is not how a lens in a spectacle looks like. Those lenses do not have a flat surface on one side like in your examples. They have two curves with a different radius; the inside radius (the one at the side of the eye) and the outside radius. How are those calculated (to start with, let's keep it to purely spherical lenses; i.e. no cylinder).
LOL
You wouldn't believe how I struggled with that same exact concept. In fact it is the reason it is one of the last in the theory series. I too wanted to see it as an "eyeglass lens" where that simply isn't possible. It is why some of us are opticians and some people are engineers and some people really understand physics. Take a deep breath, let it out... move on my friend. I feel for you. John
@@LaramyKOptical Thanks for your answer. I'm not an optician and I'm not an engineer in optics. (I'm an engineer in IT). But, I'm retired now and I just had a new prescription for my glasses and I thought it would be a good idea to try to understand what it was all about so I started to look around on the web and that's how I came to your (excellent) channel. I learned a lot already. But anyway, I would like to get an even better idea on how it all works. From what I could find, I could already deduce that for a negative prescription (negative dioptre) the radius of the inside curve has to be smaller than the radius of the outside curve. For a positive dioptre, it's the inverse. But I haven't found any practical examples up till now (real measures) so I was hoping you could shed some light on it.
@@peterdegelaen I was up at 2 AM this morning thinking about this one. I rarely reply to comments after 7 PM but yours caught my eye. Glad you read it as it was intended. You may find the videos on toric transposition helpful. You may find the How It's Made video helpful. After that, for the hard core stuff you would need a book like Modern Ophthalmic Optics from the folks at IOT. As soon as you add in those second, third or free-form curves on the back you leave the realm of basic math and basic optical theory and enter the realm of some pretty complex physics. Being a bear of little brain that stuff is outside my understanding. Don't tell anyone and it's not like I'd post it on YT or anything but I was more or a less a puppet on that one. The examples actually came from an OD who teaches optics. I didn't credit him because I didn't think he would want his name associated with a video that mocks the "p" word. The rest was vetted by Keith, the K in Laramy-K. He is an all around genius and is a real life actual physicist. Like you I couldn't get past the, "but that isn't an eyeglass lens" part. But the math is solid and the concept is correct and the Surface Power Formula certainly is a part of optics. John PS: The creation of power in a lens is the process of lens surfacing. So surfacing or maybe even generating would be terms to look for.
@@LaramyKOptical OMG! It was never my intention to make you lose sleep because of my questions. Thanks a lot for your extensive answer.
Best regards,
Peter