Prism thinning

[shubhendu]

Ok..thanks

[Lensman11]

You are mixing apples and oranges. Prism thinning has nothing to do with prentice’s rule. The goal is to make the thickness on the top and bottom of the lens equal so the overall lens can be thinner. The higher the fitting height the more prism you need, the higher the add power the more prism you need the longer the radius to the longest corner in either lower quadrant the more prism you need.

[shubhendu]

Good Morning Sir(s) thanks both of u for this valuable feedback.i m trying to find out the mathematics solution for this prism value.can I apply the Prentice rule for this.?

[lensmanmd]

Dear sir(s),I have some problem to understand the below prescription:
Re- +4.5/-2.5*155 & dcntr -2.90 in//4.90 up
Le-+4.75/-3.25*20 & dcntr-3.40 in//4.90 up
BE ADD-2.00
BE 2.37 ∆ @270
I,m not able to understand how 2.37 ∆ prism comes.

This indicates prism thinning. Avg drop is 4, but I am not understanding why the BD^ is so exaggerated. Max ^ with a +2 add should be around 1.2^, even less with a "5" up fit.

[Lensman11]

The 2.37 @ 270 seems to indicate the prism thinning. This value is usually not part of the Rx as the value should change based on the frame selection, lens design and fitting height. In addition anything over 2 diop of prism is reduced to 2 as that is the point past which the prism starts to bother some people.

[shubhendu]

Dear sir(s),I have some problem to understand the below prescription:
Re- +4.5/-2.5*155 & dcntr -2.90 in//4.90 up
Le-+4.75/-3.25*20 & dcntr-3.40 in//4.90 up
BE ADD-2.00
BE 2.37 ∆ @270
I,m not able to understand how 2.37 ∆ prism comes.

[Darryl Meister]

I have an article on prism-thinning available online: Prism-Thinning Progressive Lenses. It might provide some useful pointers for you.

[CME4SPECS]

That is why I am asking these questions. I want to give my Drs. the best possible product that I can. I believe that the lab I work for has been in the dark ages and I want to use the technology that is out there to make a better product. I want my dispensers to have a quality product that is comparable to or better than anything else they can get.
Also another question is; Is there any other type of lenses in which you would use prism thinning?

The dark ages is an understatement! Executives also need prism thinning. I have my lab relocate the oc on trifocals as well.

[Rheaopt]

That is why I am asking these questions. I want to give my Drs. the best possible product that I can. I believe that the lab I work for has been in the dark ages and I want to use the technology that is out there to make a better product. I want my dispensers to have a quality product that is comparable to or better than anything else they can get.
Also another question is; Is there any other type of lenses in which you would use prism thinning?

[QDO1]

I understand the concept of prism thinning, but we have never used this at our lab. This was in part to our former lab manager.
I am thinking about starting to do thinning, but would like to know does it make that much difference? Does it make verification any more difficult? I have computer software that will figure it, but is there certain times that you shouldn't use it? Are there any draw backs in general to starting to do prism thinning?
Sorry for so many questions.

Thanks
Steve

As a dispenser this post worries me. Most lens designs specify how prisim thinning should be applied. Prism Thinning has all sorts of implications ot the characteristics and performance of the lenses. I would hope that as a dispenser If I ordered a "XYZ" lens, that each lab would make it to the specifications laid down by the designer. Furthermore, I hope all labs would surface the same thing

How on earth are dispensers supposed to make technical judgments between lenses, if the surfacing is different between different labs for the same product

[Rheaopt]

I understand the concept of prism thinning, but we have never used this at our lab. This was in part to our former lab manager.
I am thinking about starting to do thinning, but would like to know does it make that much difference? Does it make verification any more difficult? I have computer software that will figure it, but is there certain times that you shouldn't use it? Are there any draw backs in general to starting to do prism thinning?
Sorry for so many questions.

Thanks
Steve