Thank you for your Oblique Meridians video. I have learned for the first time clearly. I have chosen this video to watch because it is in the syllabus of ABO-NCLE Practical Exam Handbook - Power in Oblique Meridian.
You might want to reverse that thinking. Join OpticianWorks and complete the program. You'll be a much better optician and be far better prepared for the day-to-day job. If you have to take the ABO it will come easy after working through OpticianWorks.
No. I think maybe OptiCampus had/has one? I know a bunch of people tried to create apps when that was a new thing. I actually had one on the original website but that got lost along the way.
@@LaramyKOptical thank you! Would it be safe to say a positive cylinder would be the exact opposite and identify the meridian with the most cylinder power?
@@timlopresti3215 I would say yes it would be. But modern lenses are built in minus cylinder form so all lens formulas are worked in minus cylinder form. Plus cylinder form is another optical "we have always done it that way" left over from a 100 years ago.
@@LaramyKOptical Thank you so much for the response. It definitely helps me have a better understanding. So if someone comes in with a prescription that includes cylinder astigmatism correction, you would expect the cylinder value always be negative? I’ve did read somewhere that an optometrist can convert a positive cylinder into a negative cylinder and rearrange a prescription so the correction remains the same but that’s probably getting 2 into the weeds!
@@timlopresti3215 LOL there is a video on that too it is called Flat Transposition. You aren't changing anything just writing it in one of two possible ways.
I’m only here to do my own prescriptions, since my prescribed glasses rarely are good enough, because of astigmatism. I bought a lens kit and frame and hopefully I can improve my eyesights for more of my working conditions. So fun!
Good for you! If you have a baseline lens power and a trial frame set you may well find something that works best for you and your specific work conditions. Just watch for over powering since we think we love minus and we don't tend to like plus.
I'm currently stuck around 6:16. I've typed in sin(68) on my phone's calculator as well as on Google's scientific calculator, and I get -0.8979277. However, I went to www.desmos.com/scientific, and I type in sin(68), and I get 0.9271838546, which is the same answer is shown on the calculator screen on this video at 6:16. I can't type in 68 then sin with the calculators I've used so far. It has to be sin(68). I have no idea why I'm getting two different answers for apparently the same function and problem...
Wow. I thank God that about 1 minute after posting this, I believe I now know the reason why I got two different answers. On my Google scientific calculator, the sin function was set to Rad, which I believe means radius. With that setting, sin(68) came out to -0.89792768068 . However, when I changed the calculator to Deg, which I believe means degrees, my answer came out to 0.92718385456 . At this point, I haven't seen the option on my Android phone change from Rad to Deg, but I can get another calculator. Yeah, now, I can continue with this video. Thanks for sharing this content!
Hi Shanelle, We make the videos available for specific reference but they probably won't function well as an end-to-end learning tool. If you sign up for OpticianWorks.com membership, you get all the videos (and more) presented in the context of 7 different courses with supporting materials, illustrations, quizes, progress tracking and much more! Thanks for watching!
Students work prism problems for Prentices Formula using the power at either 90 or 180. Just something they are used to. 180 for PD errors and 90 for OC errors.
Love the video very understandable with the calculator, but what if a question like this pops on the ABO exam and we can’t use the calculator. What would be a easier or more efficient way to solve for this problem?. Thank you again
You won't find that on any ABO exam. It should be on it but we will leave that to the side for now. Yes - you will find the 30/45/60 rule and of course flat transposition too. Plenty of other videos! John
Hi sir , i read this on a website can you explain it for us in your future lovely tutorials please 😊 By Dr.Gehad Elnahri Todays discussion will be about the correction of astigmatism by glasses The general rules for correction of astigmatism are 1)you can fully correct astigmatism in children 2)if not worn before do not fully correct above 10 yrs 3)avoid introducing cylinder for the first time above 40 4)generally do not make big cylinder changes in power all the time (0.5-1.0 max) 5)even for axes do not make more than 15 degree changes if wrong axis worn for a long time 6)you can always use the rule of spherical equivalent to put the circle of least confusion on the retina with acceptable vision 7)simple astigmatics see better than the corresponding errors because one focal line is on the retina 8)you can have meridional amblyopia when testing optotypes in astigmatics 9)sometimes the correction of astigmatism is much more tiring to the patient than the astigmatism itself 10)if your patient sees 6/6-6/12 use the cross cylinder to refine the cylinder power and axis for those wearing sharp glasses before Lets work out some examples *An 18 year female has cyclorefraction of -3.0x90 OU and needs best possible vision what will you prescribe? 1)i will under correct cylinder and there are 2 ways -change cylinder by 1.0 D at a time -give 50% of the cylinder 2)in this example it is acceptable to give -1.0/-1.5 C (according to patient personality and style of life) 3)if you give -1.0 Cx90, the remaining 2.0 cyl have a spherical eq of -1.0, so her prescription for best vision -1.0/-1.0x90 or -0.5/-1.5x90 if you use the 50% rule * a 40 yr male never worn glasses with refraction +1.0/+2.0/180 1)we will not prescribe cylinder or max 0.5 2)SE is +2.0 then apply rules of hypermetropia *a 5 yr old with ref +2.0/+3.0x180 OD +1.0/+4.0x180 OS 1)fully correct the cylinder 2)OD now +2.0 S, he may not be able to relax accommodation so you can give -1.0 Presc -1.0/+3.0x180 If u prefer minus C transpose +2.0/-3.0x90 3)OS -2.0/+4.0x180 Transpose +2.0/-4.0x90
Yasa Alwaaly, Dr Einahri's article is excellent and I would encourage opticians to read it. But, we don't cover prescribing since opticians don't really do that. Writing the actual prescription is currently the job only of ODs and MDs. Don't be shy on asking for other topics - I'm glad to do them if they fall under day-to-day opticianry. John
That is OK and (seriously) thank you for following up. If I had just posted that I would have been worried - very worried since math isn't exactly my strong point. But I'd say that one is about as vetted a video as you can get. To be honest I've got a few people in the wings just dying for me to screw up so they can pounce all over it. Lucky for me I have Keith the genius checking my work. ;-
You are wrong! A cylinder lens has no power at oblique meridians since there is no image perpendicular to those respective meridians. The only power on a cylinder lens is the power of the cross-curve. You forget the definition of power.
@@keithbenjamin6056 By telling you not to use the equation in question because it gives invalid results for oblique meridians on a single cylinder lens. Of particular concern is its misuse to calculate decentration in Prentice’s Rule. The result you are calculating actually represents an “imaginary power”, not one associated with an image. Recall the definition of lens power.
@@dsteffler54 I see your point. But, that equation has been used forever to determine "power" explicitly for use in Prentice's Rule. I am not aware of another application of it (for whatever that's worth). Are you suggesting that prism is only induced perpendicular to the axis of the cylinder? Or would you suggest some other method?
Thank u so muchhhhhhh
im just watching this while doing licensing exam in 4 hours
Thank you for your Oblique Meridians video. I have learned for the first time clearly. I have chosen this video to watch because it is in the syllabus of ABO-NCLE Practical Exam Handbook - Power in Oblique Meridian.
You might want to reverse that thinking. Join OpticianWorks and complete the program. You'll be a much better optician and be far better prepared for the day-to-day job. If you have to take the ABO it will come easy after working through OpticianWorks.
Where can I find the geometry illustrated that this formula is derived from?
Does the Rx need to be transposed with a plus cyl?
No. All optical formulas are worked in minus cylinder since all modern lenses are minus cylinder construction.
You have mentioned in other videos apps available for calculating PIOMF, any you personally recommend?
No. I think maybe OptiCampus had/has one? I know a bunch of people tried to create apps when that was a new thing. I actually had one on the original website but that got lost along the way.
This is a difficult thing to understand. Thanks for explaining it so clearly!
Thanks Sara, glad we could help!
I’m about to take a midterm on fabrication and this helps a lot!!!
Does the axis in a vision rx identify the meridian that has cylinder power or does not?
A written "prescription" when written In minus cylinder form the axis will align with no cylinder power.
@@LaramyKOptical thank you! Would it be safe to say a positive cylinder would be the exact opposite and identify the meridian with the most cylinder power?
@@timlopresti3215 I would say yes it would be. But modern lenses are built in minus cylinder form so all lens formulas are worked in minus cylinder form. Plus cylinder form is another optical "we have always done it that way" left over from a 100 years ago.
@@LaramyKOptical Thank you so much for the response. It definitely helps me have a better understanding. So if someone comes in with a prescription that includes cylinder astigmatism correction, you would expect the cylinder value always be negative? I’ve did read somewhere that an optometrist can convert a positive cylinder into a negative cylinder and rearrange a prescription so the correction remains the same but that’s probably getting 2 into the weeds!
@@timlopresti3215 LOL there is a video on that too it is called Flat Transposition. You aren't changing anything just writing it in one of two possible ways.
I’m only here to do my own prescriptions, since my prescribed glasses rarely are good enough, because of astigmatism. I bought a lens kit and frame and hopefully I can improve my eyesights for more of my working conditions. So fun!
Good for you! If you have a baseline lens power and a trial frame set you may well find something that works best for you and your specific work conditions. Just watch for over powering since we think we love minus and we don't tend to like plus.
I'm currently stuck around 6:16. I've typed in sin(68) on my phone's calculator as well as on Google's scientific calculator, and I get -0.8979277. However, I went to www.desmos.com/scientific, and I type in sin(68), and I get 0.9271838546, which is the same answer is shown on the calculator screen on this video at 6:16. I can't type in 68 then sin with the calculators I've used so far. It has to be sin(68). I have no idea why I'm getting two different answers for apparently the same function and problem...
Wow. I thank God that about 1 minute after posting this, I believe I now know the reason why I got two different answers. On my Google scientific calculator, the sin function was set to Rad, which I believe means radius. With that setting, sin(68) came out to -0.89792768068
. However, when I changed the calculator to Deg, which I believe means degrees, my answer came out to 0.92718385456
. At this point, I haven't seen the option on my Android phone change from Rad to Deg, but I can get another calculator.
Yeah, now, I can continue with this video. Thanks for sharing this content!
@@First1000HoursThank you! It's been a while since I've had to use my scientific calculator and I was so lost on this part also!
Which video do I need to start with? Your videos are not in order or numbered and it's a little confusing to know where to start.
Hi Shanelle, We make the videos available for specific reference but they probably won't function well as an end-to-end learning tool. If you sign up for OpticianWorks.com membership, you get all the videos (and more) presented in the context of 7 different courses with supporting materials, illustrations, quizes, progress tracking and much more! Thanks for watching!
Sir when power is -2.25-0.75 175
Error to 90 how can solve it
Why did you chose 90 degree in 2nd example and why you chose 180 degree in 3rd example
Students work prism problems for Prentices Formula using the power at either 90 or 180. Just something they are used to. 180 for PD errors and 90 for OC errors.
Love the video very understandable with the calculator, but what if a question like this pops on the ABO exam and we can’t use the calculator. What would be a easier or more efficient way to solve for this problem?. Thank you again
You won't find that on any ABO exam. It should be on it but we will leave that to the side for now. Yes - you will find the 30/45/60 rule and of course flat transposition too. Plenty of other videos! John
Thank you sir
sir when degree is 180 , than sin 180 will be zero... and we will not count cylindrical power in total power calculation .... sir am i right or wrong
Correct. Cylinder is only present between the two principle meridians.
Hi sir , i read this on a website can you explain it for us in your future lovely tutorials please 😊
By Dr.Gehad Elnahri
Todays discussion will be about the correction of astigmatism by glasses
The general rules for correction of astigmatism are
1)you can fully correct astigmatism in children
2)if not worn before do not fully correct above 10 yrs
3)avoid introducing cylinder for the first time above 40
4)generally do not make big cylinder changes in power all the time (0.5-1.0 max)
5)even for axes do not make more than 15 degree changes if wrong axis worn for a long time
6)you can always use the rule of spherical equivalent to put the circle of least confusion on the retina with acceptable vision
7)simple astigmatics see better than the corresponding errors because one focal line is on the retina
8)you can have meridional amblyopia when testing optotypes in astigmatics
9)sometimes the correction of astigmatism is much more tiring to the patient than the astigmatism itself
10)if your patient sees 6/6-6/12 use the cross cylinder to refine the cylinder power and axis for those wearing sharp glasses before
Lets work out some examples
*An 18 year female has cyclorefraction of
-3.0x90 OU and needs best possible vision what will you prescribe?
1)i will under correct cylinder and there are 2 ways
-change cylinder by 1.0 D at a time
-give 50% of the cylinder
2)in this example it is acceptable to give -1.0/-1.5 C (according to patient personality and style of life)
3)if you give -1.0 Cx90, the remaining 2.0 cyl have a spherical eq of -1.0, so her prescription for best vision
-1.0/-1.0x90 or -0.5/-1.5x90 if you use the 50% rule
* a 40 yr male never worn glasses with refraction +1.0/+2.0/180
1)we will not prescribe cylinder or max 0.5
2)SE is +2.0 then apply rules of hypermetropia
*a 5 yr old with ref
+2.0/+3.0x180 OD
+1.0/+4.0x180 OS
1)fully correct the cylinder
2)OD now +2.0 S, he may not be able to relax accommodation so you can give -1.0
Presc -1.0/+3.0x180
If u prefer minus C transpose
+2.0/-3.0x90
3)OS -2.0/+4.0x180
Transpose
+2.0/-4.0x90
Yasa Alwaaly,
Dr Einahri's article is excellent and I would encourage opticians to read it. But, we don't cover prescribing since opticians don't really do that. Writing the actual prescription is currently the job only of ODs and MDs.
Don't be shy on asking for other topics - I'm glad to do them if they fall under day-to-day opticianry.
John
Mr John
Im glad you always respond to my comments , I will always ask for your help thank you.
by the way im not optician im an Iraqi optometrist we study a small mix of optics and optometry in 4 years of college
Mr John
Do you know any formula to solve bi-oblique astigmatism
sorry , you are right
That is OK and (seriously) thank you for following up. If I had just posted that I would have been worried - very worried since math isn't exactly my strong point. But I'd say that one is about as vetted a video as you can get. To be honest I've got a few people in the wings just dying for me to screw up so they can pounce all over it. Lucky for me I have Keith the genius checking my work. ;-
42
You are wrong! A cylinder lens has no power at oblique meridians since there is no image perpendicular to those respective meridians. The only power on a cylinder lens is the power of the cross-curve. You forget the definition of power.
Hi Dennis! Thanks for your comment. This video might help: th-cam.com/video/r1bVUYsohqc/w-d-xo.html
@@LaramyKOptical No, it doesn’t help... it just perpetuates a misconception.
@@dsteffler54 how would you clear it up?
@@keithbenjamin6056 By telling you not to use the equation in question because it gives invalid results for oblique meridians on a single cylinder lens. Of particular concern is its misuse to calculate decentration in Prentice’s Rule. The result you are calculating actually represents an “imaginary power”, not one associated with an image. Recall the definition of lens power.
@@dsteffler54 I see your point. But, that equation has been used forever to determine "power" explicitly for use in Prentice's Rule. I am not aware of another application of it (for whatever that's worth). Are you suggesting that prism is only induced perpendicular to the axis of the cylinder? Or would you suggest some other method?
Very confusing video.