Optician Training: What Is Toric Transposition and How Is It Done? with 9 Examples

What Is Toric Transposition and How Is It Done?: We introduce you the concept using the nominal lens formula and work through nine examples with the relationship between front base curves - toric back curves and cross back curves. If you liked this video, please let us know in the comments and subscribe to our channel. Thanks!

The optical cross is the graphical representation of the two primary or principal powers on a lens. Toric transposition is the graphical representation of the powers (or curves) on the front surface of the lens and the back surface of the lens. DL = D1 + D2 or FL = F1 + F2. For optician training or ABO NOCE study, this lesson is based on an exercise sheet that a member asked for help reviewing. The lesson covers the concept of toric transposition and then goes on to work nine individual step-by-step problems.

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This video lesson is sponsored by Laramy-K Optical

Laramy-K Optical is a digital uncut and coating lab unlike any other. The only exclusively uncut lab in the country; we provide our customers with independent, high-end alternatives to corporate brands. Through craftsmanship, technology, and independent, innovative vendors like Younger, IOT, A&R, and Quantum Innovations we offer our customers the Integrity portfolio of freeform lenses and coatings. Made in the USA, the Integrity brand is not a generic house-brand, but is the absolute best available, designed to give the wearer that “wow!” experience.

In addition to the digital line, we still offer conventional surfacing, including glass. Maintaining traditional equipment gives our customers vastly more flexibility in their dispensing, particularly when it comes to more difficult prescriptions.

[LaramyKOptical]

Hey - John here. Just to be clear: These 9 examples came from a question sheet that was sent to me by a member. She asked me to work them out for her so I did. Someday I'll do another one and use examples that are a little more realistic. Some of the numbers on the sheet were a little, well, odd. Thanks for understanding.

[bhuvana]

The prescription +2.00 DS/+2.00 DC x 135 is made as a lens with a -4.00 D toric base curve.Disregarding lens thickness, what is the power of the front surface

[DaveViner]

Awesome! Nice and clear explanation, thank you!

[DATARPRASAD]

thanks for all the videos, I am interested in how to produce aspheric lens, their materials if any and process

[fgzy]

Hi John. Can you explain why transposition doesn't change the optical power of the final product? I'm trying to understand how that's possible, given that a spherical power is the same on all meridians. For example, if a prescription is written as +1.50 / -2.00 x 90 and you transcribe it to -0.50 / +2.00 x 180, then the power on all meridians becomes -.50 which is an entirely different type of lens (concave with negative power) instead of convex.

[sparsotam]

Thank you for the videos. Just wondering when transposing into toric form and we are given the SPH Curve, how do we know when to do simple transposition first. I am unsure when should the given cyl be positive and when should it be negative.

[tariqshahtalib]

Sir after changing additional number prescription to near vision prescription can we transpose that prescription if transposition should apply??

[nona]

Hi thank you for your explaning very well though I have aqu!
Last step in putting the cyl outcome we put it the sign - bacause it's cyl or according to substrate the more num and less numm?
Thank you

[vic-arenal]

I think the one at the right is the back curve, while the left is the cross curve.

[nurgulsantiago]

There is some video on YouTube. They change the BC axis 90 degree apposite, why?

[eyesightsonalighosh]

If you generate power in this way 🙄 i think u will lose your lens in case of bifocals and progressive lenses as those transpositions wrong 😢