In the first example using Vogel's rule, where does the -1.00 come from? At some point do we half the cylinder power? I'm a bit confused because there were no steps that would indicate how do come up with that -1.00? Please help!
Did you ever get an answer to this question? I’m highly confused especially with the other examples having different numbers that I don’t know where it came from 😩
Thank you for the video! Can you explain why you are halving the cylinder power in the Vogel's rule example? Everything else makes sense except for that.
Both the methods below work off the spherical equivalent of the given prescription. The formula to determine the spherical equivalent of any Rx is: Rx sphere power added to 1/2 the cylinder power. If the Rx is a sphere like -2.50 then you work with the -2.50. Spherical equivalents are also used in other formulas and when working with contact lenses. The most basic rule is that you always want the base curve to be as close to +6.00 as you can get and still have the Rx work. In theory +6.00 should always give you the best possible combination of curves for weight, optics, etc. Study the chart below. You will want to remember that the higher the plus power, the higher plus the base curve will become. The more minus the power (less plus power to minus power) the lower plus the base curve will become. A high minus Rx may even have a base curve of +0.25 or even 0.00. To do that you can use Vogel’s Rule which is this: For a plus prescription: Base Curve = Rx spherical equivalent + 6.00D For a minus prescription: Base Curve = 1/2 the Rx spherical equivalent + 6.00D I don't you'll go wrong in thinking of spherical equivalent as an averaging of powers.
Sir In prescription i have -1 sphere and -5 cylinder in right eye and-2 sphere and - 5 cylinder in left eye So what is the power of lense It is below 4 or exceed this Please help
Arun - You want to watch the video on The Optical Cross. The nominal lens formula is something else. The lens you describe has -1.00 power in one meridian and -6.00 power in another 90 degrees away. John
Oh! Hey - yeah that's it! Thanks, that has been bothering me. Maybe next time we can do a sing along. But Keith always edits out any singing I do. I wonder why?
I saw the video where u read a optical poem. It was good. If you sang an optical song, Keith would have to keep it in! It could be a sing-a-long with the lyrics on the bottom of the screen. And a bouncing eyeball could be used to show what lyrics you are on.
Speaking of Julie Andrews. Did you ever notice that the want ad for the nanny in Mary Poppins actually makes for a good want ad for an optician? Weird! If you want this choice position Have a cheery disposition Rosy cheeks, no warts! Play games, all sort You must be kind, you must be witty Very sweet and fairly pretty Take us on outings, give us treats Sing songs, bring sweets Never be cross or cruel Never give us castor oil or gruel Love us as a son and daughter And never smell of barley water If you won't scold and dominate us We will never give you cause to hate us We won't hide your spectacles So you can't see Put toads in your bed Or pepper in your tea Hurry, Nanny! Many thanks Sincerely,
Thanks as always for the helpful videos. Could you possibly make one explaining how center thickness can negativity impact a final completed pair of glasses (when it doesn't meet tolerance standards)? Thank you!
Center thickness can only be out of "tolerance" in a minus and that only happens when the CT setting in the generator is set incorrectly resulting in a lens with an extremely thin CT. Think paper thin, think flexible, think I could put my finger through this thin. That should always be caught at the lab before it ever gets to an optician let alone a customer. Watch the 3 videos on Verification - Final Inspection. Checking lens thickness and having calipers is a relic from the days of 100% manual calculations and manual lens generating on Coburn's. 30+ years ago.
@Laramy-K Optical thank you thank you!! I currently work at a place where checking center thickness is a step when trouble shooting glasses and so I was a bit unsure of how that could negatively impact a patient opticaly 🤔
You are amazing teacher I would like to ask you about base curve or front curve How can I choose if example sph +6.25 cyl _ 150 axis 90 Example sph +8 cyl _2 axis 180 Sph +23 how choose base curve rx after calculate power plz
Look for Part 1 in that same series. I cover Vogel's Rule there. You also have some base curve charts floating around too. None of that matters now since computers do all the calculations for us. Stock lenses already run on best choice. Surfaced lenses the LMS decides which curve is best. John
Can you clarify what you mean by contact lens prescription to trial frame? Depending on the type of contacts the prescription is going to be different from the optical rx due to vertex and compensated powers.
I'm confused about the minus powers of the Vogel's Rule; I'm not understanding why we divide the cylinder power in half? Per the Rule is 1/2 the sphere equivalent (Sph + Cyl) then divide by 2. Did I miss an explanation somewhere? Thanks!
You can't. It would depend on the material and what the surfacing equipment was set to. Your surfacing lab should be able to tell you. Do you mean edge thickness in a minus? Why CT for a minus? John
@@LaramyKOptical thankyou sir for telling but I am saying power of spherical value is -2.25 and power of cylindrical value is -1.75 and additional power is 1 how we set the center thickness in our system for cutting optical lens please tell me calculation and how I set the base value in our system
@@vikasmishra2697 Whoa OK without knowing what equipment and a million other things --- you would want your CT to end up at the minimum that whatever standard you are using allows. If it is 2.0 then you would set the CT at 2.0. I'd go to the equipment manufacturer and ask them or dig up a manual online maybe. Is this auto equipment or manual equipment? Like a Coburn with a diamond wheel old or something else?
Biana, The videos work best when you are working through the www.OpticianWorks.com program. The RUclips page is not in any set order. The program is a step-by-step where things build in sequence. John
Hello! Thank you for such an informative video. at 6:17 I'm confused as to why we are using -1.00 instead of -2.00. Thank you!
Hi Laramy, here again listining your interesting theme, now Base Curve Part 1...
Thank you so very much sir plz describe the cross compound lens sir
In the first example using Vogel's rule, where does the -1.00 come from? At some point do we half the cylinder power? I'm a bit confused because there were no steps that would indicate how do come up with that -1.00? Please help!
Did you ever get an answer to this question? I’m highly confused especially with the other examples having different numbers that I don’t know where it came from 😩
Thank you for the video! Can you explain why you are halving the cylinder power in the Vogel's rule example? Everything else makes sense except for that.
Both the methods below work off the spherical equivalent of the given prescription. The formula to determine the spherical equivalent of any Rx is:
Rx sphere power added to 1/2 the cylinder power. If the Rx is a sphere like -2.50 then you work with the -2.50. Spherical equivalents are also used in other formulas and when working with contact lenses.
The most basic rule is that you always want the base curve to be as close to +6.00 as you can get and still have the Rx work. In theory +6.00 should always give you the best possible combination of curves for weight, optics, etc.
Study the chart below. You will want to remember that the higher the plus power, the higher plus the base curve will become. The more minus the power (less plus power to minus power) the lower plus the base curve will become. A high minus Rx may even have a base curve of +0.25 or even 0.00.
To do that you can use Vogel’s Rule which is this:
For a plus prescription: Base Curve = Rx spherical equivalent + 6.00D
For a minus prescription: Base Curve = 1/2 the Rx spherical equivalent + 6.00D
I don't you'll go wrong in thinking of spherical equivalent as an averaging of powers.
Sir In prescription i have -1 sphere and -5 cylinder in right eye and-2 sphere and - 5 cylinder in left eye So what is the power of lense It is below 4 or exceed this Please help
Arun - You want to watch the video on The Optical Cross. The nominal lens formula is something else. The lens you describe has -1.00 power in one meridian and -6.00 power in another 90 degrees away. John
"Let's start at the very beginning. A very good place to start." Beginning lines to the song "Do Re Mi" from the musical "The Sound of Music"
Oh! Hey - yeah that's it! Thanks, that has been bothering me. Maybe next time we can do a sing along. But Keith always edits out any singing I do. I wonder why?
I saw the video where u read a optical poem. It was good. If you sang an optical song, Keith would have to keep it in! It could be a sing-a-long with the lyrics on the bottom of the screen. And a bouncing eyeball could be used to show what lyrics you are on.
Love it! John
Speaking of Julie Andrews. Did you ever notice that the want ad for the nanny in Mary Poppins actually makes for a good want ad for an optician? Weird!
If you want this choice position
Have a cheery disposition
Rosy cheeks, no warts!
Play games, all sort
You must be kind, you must be witty
Very sweet and fairly pretty
Take us on outings, give us treats
Sing songs, bring sweets
Never be cross or cruel
Never give us castor oil or gruel
Love us as a son and daughter
And never smell of barley water
If you won't scold and dominate us
We will never give you cause to hate us
We won't hide your spectacles
So you can't see
Put toads in your bed
Or pepper in your tea
Hurry, Nanny!
Many thanks
Sincerely,
Thanks as always for the helpful videos. Could you possibly make one explaining how center thickness can negativity impact a final completed pair of glasses (when it doesn't meet tolerance standards)? Thank you!
Center thickness can only be out of "tolerance" in a minus and that only happens when the CT setting in the generator is set incorrectly resulting in a lens with an extremely thin CT. Think paper thin, think flexible, think I could put my finger through this thin. That should always be caught at the lab before it ever gets to an optician let alone a customer. Watch the 3 videos on Verification - Final Inspection. Checking lens thickness and having calipers is a relic from the days of 100% manual calculations and manual lens generating on Coburn's. 30+ years ago.
@Laramy-K Optical thank you thank you!! I currently work at a place where checking center thickness is a step when trouble shooting glasses and so I was a bit unsure of how that could negatively impact a patient opticaly 🤔
You are amazing teacher I would like to ask you about base curve or front curve
How can I choose if example sph +6.25 cyl _ 150 axis 90
Example sph +8 cyl _2 axis 180
Sph +23 how choose base curve rx after calculate power plz
Look for Part 1 in that same series. I cover Vogel's Rule there. You also have some base curve charts floating around too. None of that matters now since computers do all the calculations for us. Stock lenses already run on best choice. Surfaced lenses the LMS decides which curve is best. John
Nice video , sir please make a video on contact lens prescription calculation to traile frame lenses
Sorry - But we cannot find a contact lens specialist to contribute to the site. If we ever do we can add it to the video list. John
Can you clarify what you mean by contact lens prescription to trial frame? Depending on the type of contacts the prescription is going to be different from the optical rx due to vertex and compensated powers.
I'm confused about the minus powers of the Vogel's Rule; I'm not understanding why we divide the cylinder power in half? Per the Rule is 1/2 the sphere equivalent (Sph + Cyl) then divide by 2. Did I miss an explanation somewhere? Thanks!
That isn't spherical equivalent.
Sir how we calculate the ct in lens when our spherical value is -2.25 and cyl value -1.75 and addition value 1
You can't. It would depend on the material and what the surfacing equipment was set to. Your surfacing lab should be able to tell you. Do you mean edge thickness in a minus? Why CT for a minus? John
@@LaramyKOptical thankyou sir for telling but I am saying power of spherical value is -2.25 and power of cylindrical value is -1.75 and additional power is 1 how we set the center thickness in our system for cutting optical lens please tell me calculation and how I set the base value in our system
@@vikasmishra2697 Whoa OK without knowing what equipment and a million other things --- you would want your CT to end up at the minimum that whatever standard you are using allows. If it is 2.0 then you would set the CT at 2.0. I'd go to the equipment manufacturer and ask them or dig up a manual online maybe. Is this auto equipment or manual equipment? Like a Coburn with a diamond wheel old or something else?
From which lesson should I start ?
Biana, The videos work best when you are working through the www.OpticianWorks.com program. The RUclips page is not in any set order. The program is a step-by-step where things build in sequence. John
im confused, how do we calculate spherical equivalent?
See: OpticianWorks.com
videos are excellent just wish this one moved a little slower
Sorry about that - sometimes once I get rolling, well... you can always watch it again. John
Click on the video setting icon and alter the playback speed. John will sound a little drunk but it will be slower paced. 😅
I enjoy your videos
But what's the reason for these greeeeen hands???😌
That's my helper. He only stops by a few times a year. He is kind of shy so all you get to see are his hands.
Nice😊👌
Merhabalar kral benim şu odevlere bı bakar mısın 🇹🇷🇹🇷🇹🇷