Thanks for the stepwise solution. For the first example with soluton of 2.9 prism diopters as well as in earlier videos, you show answer choice to select to be: 2.9 prism diopter BO R and 2.9 prism diopter BO L. What if along with this answer choice there is a choice that is: 2.9 prism diopter BO OU? Which one to select?
I am having a big issue determining base direction when pds are narrow/wide on plus/minus lenses. When you describe the direction for the plus lens it makes sense... but when I map it out for the minus lens I want it to have the same direction because it utilizes the same temporal triangle, which is what you point out to look for
Heather Ann, Wait for this weeks video coming out tomorrow (Thursday 7/27). I do an example with minus lens profiles. In the meantime I'd double check that you are drawing the profiles in the correct orientation and then once you have the "triangle" over the pupil go ahead and erase the other one. Never forget the golden rule: The eyes don't move the lenses move! Yeah, gotta admit I still have to look twice myself - heck it is confusing... John
Thank you for your videos! Quick question. In example one, wouldn't it be -1.2 and -1.7 giving you a total of NEGATIVE 2.9 diopters base out? Rather than positive 2.9??
Sir have a issue of the SIN USED HERE the sin of 114 square and sin of 43 square would be sin 114 square = 0.69527892358 and sin 43 square =0.98512036773 will there be any wrong in calculation
Not sure exactly what you are asking but - PD error is at 180 but the Rx isn't. The difference we get is in degrees and degrees aren't a mathematical function that works in a formula until we use the sine of the degree. Sine is a trig function for angles.
Does the 2nd example pass tolerance or no? 0.3 prism in left lens? on Ansi tolerance chart shows if the power is more than 3.37 only 1 mm is allowed ?!
Using the mm rule the glasses would be spot-on regardless since both R and L were pushed up 6mm. Using the actual error created it is right on the edge. These aren't examples about tolerance or standards but about the concept of prism error created by movement of the OCs.
Anything outside very basic 0-180 or (not and) 90 you have resultant prism. There are two other videos that cover how to work with that. In fact it is pretty rare that you ever stumble on a 0-180 or a 90 error with simple powers. Keep in mind that most of the Prentices formula stuff we work with is more for concept than actual day-to-day use. If it were up to me we would spend our time on resultant prism not Prentices formula but that isn't what people want. People want to "pass the ABO" not actually understand the kinds of prism they might actually encounter. John
Thanks for the clarification..another doubt is I have gone through a problem(bifocal segment top)which ask to calculate prism in both distance and reading addition and combining it. Where can i refer for this type of sums..And if u could post videos regarding sums on magnification of lenses it would be helpful. Thanks
@@adarshayyappa5502 I'd grab a copy of Stoner's Optical Formula Tutorial (available on Amazon) where she covers image jump and using unlike segment types to correct for imbalance. Also see my video on Image Jump. Beyond that I don't know of anything else to do with lined segments and "prism." John
i understand the steps now but my math keeps giving me a different number for example 2 and 3 sin13 squared is .1765 but you have something else written is there an explanation for this?
Thank you sir for your work, you explained the concepts much clearer than the materials provided by the company I work at.
Thanks for the stepwise solution. For the first example with soluton of 2.9 prism diopters as well as in earlier videos, you show answer choice to select to be: 2.9 prism diopter BO R and 2.9 prism diopter BO L. What if along with this answer choice there is a choice that is: 2.9 prism diopter BO OU? Which one to select?
Depends on cancelling or compounding. The answer is written in two different ways.
I am having a big issue determining base direction when pds are narrow/wide on plus/minus lenses. When you describe the direction for the plus lens it makes sense... but when I map it out for the minus lens I want it to have the same direction because it utilizes the same temporal triangle, which is what you point out to look for
Heather Ann, Wait for this weeks video coming out tomorrow (Thursday 7/27). I do an example with minus lens profiles. In the meantime I'd double check that you are drawing the profiles in the correct orientation and then once you have the "triangle" over the pupil go ahead and erase the other one. Never forget the golden rule: The eyes don't move the lenses move! Yeah, gotta admit I still have to look twice myself - heck it is confusing... John
Thank you for your videos! Quick question. In example one, wouldn't it be -1.2 and -1.7 giving you a total of NEGATIVE 2.9 diopters base out? Rather than positive 2.9??
Sir have a issue of the SIN USED HERE the sin of 114 square and sin of 43 square would be sin 114 square = 0.69527892358 and sin 43 square =0.98512036773 will there be any wrong in calculation
I think you need to switch from RAD to DEG on the calculator?
i. also noticed this when i plug into calculator i get what you get? are we doing something wrong??
Can you please tell me why you “squared” the difference between 180 and the axis given in our Rx? Why do we do that?
Not sure exactly what you are asking but - PD error is at 180 but the Rx isn't. The difference we get is in degrees and degrees aren't a mathematical function that works in a formula until we use the sine of the degree. Sine is a trig function for angles.
Does the 2nd example pass tolerance or no? 0.3 prism in left lens? on Ansi tolerance chart shows if the power is more than 3.37 only 1 mm is allowed ?!
Using the mm rule the glasses would be spot-on regardless since both R and L were pushed up 6mm. Using the actual error created it is right on the edge. These aren't examples about tolerance or standards but about the concept of prism error created by movement of the OCs.
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ua-cam.com/video/RYXj69pK9X4/v-deo.htmlsi=skhaUiq1grAYROUq
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But does it pass or no based on tolerance chart?
Could you please explain what if there are decentration error in both PD as well as vertical height comes together
Anything outside very basic 0-180 or (not and) 90 you have resultant prism. There are two other videos that cover how to work with that. In fact it is pretty rare that you ever stumble on a 0-180 or a 90 error with simple powers. Keep in mind that most of the Prentices formula stuff we work with is more for concept than actual day-to-day use. If it were up to me we would spend our time on resultant prism not Prentices formula but that isn't what people want. People want to "pass the ABO" not actually understand the kinds of prism they might actually encounter. John
Thanks for the clarification..another doubt is I have gone through a problem(bifocal segment top)which ask to calculate prism in both distance and reading addition and combining it. Where can i refer for this type of sums..And if u could post videos regarding sums on magnification of lenses it would be helpful. Thanks
@@adarshayyappa5502 I'd grab a copy of Stoner's Optical Formula Tutorial (available on Amazon) where she covers image jump and using unlike segment types to correct for imbalance. Also see my video on Image Jump. Beyond that I don't know of anything else to do with lined segments and "prism." John
i understand the steps now but my math keeps giving me a different number for example 2 and 3 sin13 squared is .1765 but you have something else written is there an explanation for this?
Check that your calculator is set on DEG.