Thank you so much John, I am a current opticianry student from Canada. And COVID-19 really hit us as school are going online and closed physically. I found you videos are the best way for me to visualise and study for it besides my textbook. With that said I much appreciated on your effort to provide us educational video for free. You are really making a difference to the field. Cheers.
Using a lot of Play Doh, make a shape of a half football and make a slice through the steepest section and show cross section. Do that for for the different angles and show the different cross sections. I believe this will show things better.
Dear John can you please make a video about Axis measure. I heard that you take the angle from the left of both eyes. Also a video about the total correction with respect to Axis Angle✌
Can you please explain how axis are put into cylindrical lenses? And also how to be sure that an optician has put the right axis into the prescription glasses? Thanks :)
No, no online ordering of finished lenses from Laramy-K for the consumer. We are a wholesale optical lab not a retail store. We may have a customer near you where you could get our lenses. Email me through the OpticianWorks website.
Hello John Ihave prescription for my left eye as follow (OS: sphere, cylinder, axis) -7.25 -3.75 164 Does that mean that i have nyopia of -7.25 and -3.75 astigmatims or a combined myopia -7.25+(-3.75)=-11Diopters strength. My OD: +1,25 -2.50 157 Thank you for you help or to anyone who answers this question
Next to nothing I'm afraid. I can't imagine a cylinder lens being part of a camera lens but they may well be. Everything changes when dealing with bi-convex shapes and lenses in series and lenses in contact. I'm 100% sure you could find some engineer types on any internet photography group that would know. John
Hello Master Sensei..I am designing a frame for outdoor and looking to install rx lenses..will a frame curvature of 4.5 degrees work for rx trivex lense? Is there an ideal curvature for trivex rx lenses..please school me
Base curve is determined by the lens power not the frame. Matching lens base curve and frame base curve comes down to the edger. The better the edger the better the match. Check out the rest of the videos for more on base curve selection: mail.google.com/mail/u/0/#inbox
I have question about DpE If patient has vertical DPE what is the wearing issues may experience at the near visual point when wearing multifocal or progressive lens? Thanks in advance John.
OK Still not 100% sure what that means. If one eye is minus and the other is plus the add power (near visual point) still works the same. If the "prescription" calls for prism and the powers and directions are different then they should be there to balance vision or in other words eliminate any issues. There is slab-off, there is prism thinning, there is prism but nothing that I know of "different prismatic effect." Again, not sure but as I mention in several videos, "progressives aren't for everyone."
Sure stock single vision lenses with cylinder can be done in an hour. Cutoff is usually around 3 diopters of cylinder but finished uncut go out much higher.
Just to be annoying: with a cylinder, when you dice up your cross-sections into those “180 pieces”. You ought not describe those upper curved profiles as “spheres”. The 90 degree perpendicular cut, yes, is spherical (produces half circle cross-section [the further + 90 degree longitudinal cut would produce a rectangle (plano)]. But the upper curves of the cuts between those extremes are actually ellipsoidal, rather than spherical. elLIPSoidal, kinda like our beaks.
The video Understanding Cylinder wouldn't be a great one to help with understanding base curve. There are two or three others related to that - toric transposition. Sounds like you need OpticianWorks.com.
