Hí! Could you explain in some of your future videos how the JCC works? Or rather my question is, why as the cyl will be a half dioptre increased , schould be the sphere only a quartet increased? In my practice it works very well and I do that always like that. But it is for me just a roule ,and I miss the conception behind of it. Thank you for your answer , and best wishes from me to You, Gàbor from Budapest...
So, what I am wondering for finding the angle: why don't we just give the patient a 0.25 cylinder in any direction and let them turn the knob themself until they find the most optimal point. Much less iterative approximation needed. Then we can focus on tuning in on the power (and then let the patient fine-tune the angle with the final value). Or is cross cyl test used as it emphasizes the differences ? Personally, I have a strong cylinder, so for me 1 or 2 degrees 'off' are _very_ noticeable - so maybe I am biased towards how 'easy' the angle to find would be ?
I have been in many doctors but unfortunately I cannot get correct prescription. When I have -1.25 sphere and -1 cylinder on both eyes my left eye (which is not main) see better when they add extra 0/25 to my right eye everything is perfect, but after some time my right eye starts hurting. I tried those glasses for 3 month but returned to my similar lenses for both eyes. Now my left eeye see better and doctors says it's wrong. I cannot tolerate that 0.25 extra sphere. I tried different cylinder combination and but still have pain. What should I do. help
Because minus cyls are more common in practice for manufacturing glasses - cyls usually go to concave part of the lens, thus minus. Also, both plus and minus cyls at the end yield the same effect but at 90 degree angle difference. So, - 1D at 0 degrees would be the same as +1D at 90 degrees. In the very end it doesn't matter which one you use as long as you compensate for it with correct sphere to achieve zero sphere equivalent before adding more +/- corrections to that.
At first, you added -0.50cyl, and subsequently increased +0.25spherical lens. However, the ending was only -0.25cyl. As it is less than 50 diopters, why the change of increased +0.25spherical lens was still there? Why not starting again with the previous spherical lens and adding -0.25cyl?
The short answer - to avoid overminusing and to prefer slight overplusing instead because there was no precise enough lens with .125 deciaml precision. The long answer is as follows. Disclaimer: I'm not a professional, though; just been reading about optics lately. He started with - 3.25sph for general correction, which patient liked. Then he added - 0.5cyl for a course test to determine the axis. Then at 6:20 he got the axis correct and started to determine the power of cyls required. To do that, he had to compensate for the cyls to make the spherical equivalent the same as when he started (which is - 3.25). The formula for spherical equivalent is sph + cyl/2. So, he now had - 3.25 + (- 0.5 / 2) = - 3.5 but he needed to get - 3.25 back, so he added + 0.25 by replacing - 3.25 with - 3.0. To simplify, the rule of thumb is: for every + 0.50 diopter of cylinder power removed, add + 0.25 diopter to the sphere. Adding - 0.5 counts as removing + 0.5, I guess. Then at 6:48 he took a - 0.25 cyl and by flipping it he essentially was adding / removing - 0.25cyl (because when you flip minus cyl it's the same as adding plus cyl). The patient replied that he liked the - 0.25 added to the opposite axis, which meant that - 0.5 on current axis was too strong and should be reduced. So at 7:55 the doctor replaced - 0.5cyl with - 0.25cyl. At this point we might think that it should mean we need to add - 0.25 / 2 = - 0.125 to sph to get back initial sph of - 3.25, which means he should have replaced - 3 with - 3.125 but there is no such lens with value of - 3.125, so he left it as is. Also, the rule of thumb here is that if the patient feels no difference or if required difference is so small that there is no such lens value, you should prefer less minus to avoid overminusing. In this case we end up with - 3.125 sph equivalent instead of initial - 3.25 sph and, I guess, this is acceptable. So, to answer your question - yes, the doctor could go back to closest largest minus and add - 0.25cyl back and get that - 3.25sph, but then the total spherical equivalent would become - 3.25sph + (- 0.25cyl / 2) = - 3.375 sph equivalent. So, the doctor had two inaccurate lens choices - the one that yields - 3.125 sph equivalent and the one that yields - 3.375 sph equivalent, but no way to get back those - 3.25 sph equivalent. And the doctor choose the option with less minuses, which is to leave - 3.00sph and get - 3.125 sph equivalent at the end. At 8:11 the doctor did final checks with adding - 0.25 cyl back and doing some flipping - if astigmatic correction was done right then the patient should see no difference anymore.
I bought a trial lens set for my own prescription use. And I rotate it until clear. I guess they don’t trust the patient to use their judgement. There may be a good reason for this.
I don't understand, when you have an astigmatism, do they add the minus cyl to the sphere diopter, or is it just the cylinder number in the axis and the rest of the lens is the full diopter strength?
stargate20 because the power in two meridians are different. So there is a need to use of a cylinder beside spherical power in correcting these two meridians
Since he is holding the cross cyl manually in his hand it isn't perfectly aligned to the patiants eye (it is too far in the upper left hand corner) thus the perspectiv givs us the illusion it is placed somewhere around 20 to 25 degrees. If you want to know the actuall position you need to look at the indicator on the cross cyl and compare its angle to the degree scale on the outer rim.
Hi. your x-cyl technique is prone to error! For instance, when giving a patient choice of cyl rotation, you should give three choices - one, two or no difference. You should also rotate the x-cyl quicker and repeat the test twice in each position.
This is the first time, as a layperson, that I've understood what's going on in this process. Excellent video!
your video is very useful. it has helped me to understand better on jcc. thank you
absolutly great job.i understood it very well
Thank for clarifying JCC.
Thanks for make me improve
Very Nice.
Thankyou.
very good thanks
Thank youuuu 😊😊😊
Thank you
Excellent check - if necessary.
Hí! Could you explain in some of your future videos how the JCC works? Or rather my question is, why as the cyl will be a half dioptre increased , schould be the sphere only a quartet increased?
In my practice it works very well and I do that always like that. But it is for me just a roule ,and I miss the conception behind of it. Thank you for your answer , and best wishes from me to You, Gàbor from Budapest...
So, what I am wondering for finding the angle: why don't we just give the patient a 0.25 cylinder in any direction and let them turn the knob themself until they find the most optimal point. Much less iterative approximation needed. Then we can focus on tuning in on the power (and then let the patient fine-tune the angle with the final value). Or is cross cyl test used as it emphasizes the differences ? Personally, I have a strong cylinder, so for me 1 or 2 degrees 'off' are _very_ noticeable - so maybe I am biased towards how 'easy' the angle to find would be ?
I wish I had read further into the comments before asking. This is the same question i have
That's a good idea aswell for high cyl correction
when u changed the power of the cyl down to -0.25 did u have to change the power of the sphere back up?
I have been in many doctors but unfortunately I cannot get correct prescription. When I have -1.25 sphere and -1 cylinder on both eyes my left eye (which is not main) see better when they add extra 0/25 to my right eye everything is perfect, but after some time my right eye starts hurting. I tried those glasses for 3 month but returned to my similar lenses for both eyes. Now my left eeye see better and doctors says it's wrong. I cannot tolerate that 0.25 extra sphere. I tried different cylinder combination and but still have pain. What should I do. help
hi! why you chose the minus cyl to start when estimating whether the patient suffered from astigmatism? Why not the plus cyl?
Because minus cyls are more common in practice for manufacturing glasses - cyls usually go to concave part of the lens, thus minus. Also, both plus and minus cyls at the end yield the same effect but at 90 degree angle difference. So, - 1D at 0 degrees would be the same as +1D at 90 degrees.
In the very end it doesn't matter which one you use as long as you compensate for it with correct sphere to achieve zero sphere equivalent before adding more +/- corrections to that.
@@camelCased Oh wow i didn’t know this and this is so interesting, thank you so much
is it possible for you to demonstrate this for a larger cyl?
Ah brilliant I'll go find it! Thanks for your comment
At first, you added -0.50cyl, and subsequently increased +0.25spherical lens. However, the ending was only -0.25cyl. As it is less than 50 diopters, why the change of increased +0.25spherical lens was still there? Why not starting again with the previous spherical lens and adding -0.25cyl?
The short answer - to avoid overminusing and to prefer slight overplusing instead because there was no precise enough lens with .125 deciaml precision.
The long answer is as follows. Disclaimer: I'm not a professional, though; just been reading about optics lately.
He started with - 3.25sph for general correction, which patient liked.
Then he added - 0.5cyl for a course test to determine the axis.
Then at 6:20 he got the axis correct and started to determine the power of cyls required. To do that, he had to compensate for the cyls to make the spherical equivalent the same as when he started (which is - 3.25). The formula for spherical equivalent is sph + cyl/2. So, he now had - 3.25 + (- 0.5 / 2) = - 3.5 but he needed to get - 3.25 back, so he added + 0.25 by replacing - 3.25 with - 3.0. To simplify, the rule of thumb is: for every + 0.50 diopter of cylinder power removed, add + 0.25 diopter to the sphere. Adding - 0.5 counts as removing + 0.5, I guess.
Then at 6:48 he took a - 0.25 cyl and by flipping it he essentially was adding / removing - 0.25cyl (because when you flip minus cyl it's the same as adding plus cyl). The patient replied that he liked the - 0.25 added to the opposite axis, which meant that - 0.5 on current axis was too strong and should be reduced. So at 7:55 the doctor replaced - 0.5cyl with - 0.25cyl. At this point we might think that it should mean we need to add - 0.25 / 2 = - 0.125 to sph to get back initial sph of - 3.25, which means he should have replaced - 3 with - 3.125 but there is no such lens with value of - 3.125, so he left it as is. Also, the rule of thumb here is that if the patient feels no difference or if required difference is so small that there is no such lens value, you should prefer less minus to avoid overminusing. In this case we end up with - 3.125 sph equivalent instead of initial - 3.25 sph and, I guess, this is acceptable.
So, to answer your question - yes, the doctor could go back to closest largest minus and add - 0.25cyl back and get that - 3.25sph, but then the total spherical equivalent would become - 3.25sph + (- 0.25cyl / 2) = - 3.375 sph equivalent. So, the doctor had two inaccurate lens choices - the one that yields - 3.125 sph equivalent and the one that yields - 3.375 sph equivalent, but no way to get back those - 3.25 sph equivalent. And the doctor choose the option with less minuses, which is to leave - 3.00sph and get - 3.125 sph equivalent at the end.
At 8:11 the doctor did final checks with adding - 0.25 cyl back and doing some flipping - if astigmatic correction was done right then the patient should see no difference anymore.
Plesse tell me cylinder 0.50 and 6/6
Could you explain why the patient cannot rotate the cylinder themselves till the letters/shape stand up straight on their own?
I bought a trial lens set for my own prescription use. And I rotate it until clear. I guess they don’t trust the patient to use their judgement. There may be a good reason for this.
@@miscchan0001 I too bought a trial lens kit and that is what I do. I wonder if it goes beyond anything than trust?
They have not been trained for that to avoid damage of the trial frame.
quit blinking for one second
I don't understand, when you have an astigmatism, do they add the minus cyl to the sphere diopter, or is it just the cylinder number in the axis and the rest of the lens is the full diopter strength?
stargate20 because the power in two meridians are different. So there is a need to use of a cylinder beside spherical power in correcting these two meridians
i meed an exemple when you chose the +cyl
is it the arbitrary choice ?
okay thanks you
top check !!
Last step was confusing. Can you make it better?
Put +1.00 if he see blur all the letter..it means thats correct.
4:06 that position should be 35 and 125.. why does it look like he places cross cyl at 25 or 20 instead of 35
Since he is holding the cross cyl manually in his hand it isn't perfectly aligned to the patiants eye (it is too far in the upper left hand corner) thus the perspectiv givs us the illusion it is placed somewhere around 20 to 25 degrees.
If you want to know the actuall position you need to look at the indicator on the cross cyl and compare its angle to the degree scale on the outer rim.
@@Glitsch99 i know how to align.. i was just wondering that he is aligning some other axis and telling others.. but i know now.. thanks
Hi. your x-cyl technique is prone to error! For instance, when giving a patient choice of cyl rotation, you should give three choices - one, two or no difference. You should also rotate the x-cyl quicker and repeat the test twice in each position.