Results 1 to 11 of 11

Thread: Prism thinning

  1. #1
    OptiBoard Apprentice
    Join Date
    Nov 2005
    Location
    Cape Girardeau, Missouri
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    49

    Prism thinning

    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

  2. #2
    Bad address email on file QDO1's Avatar
    Join Date
    Sep 2005
    Location
    UK
    Occupation
    Dispensing Optician
    Posts
    1,961
    Quote Originally Posted by 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
    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

  3. #3
    OptiBoard Apprentice
    Join Date
    Nov 2005
    Location
    Cape Girardeau, Missouri
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    49
    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?

  4. #4
    Master OptiBoarder
    Join Date
    Jun 2000
    Location
    California
    Occupation
    Dispensing Optician
    Posts
    2,814
    Quote Originally Posted by 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?
    The dark ages is an understatement! Executives also need prism thinning. I have my lab relocate the oc on trifocals as well.

  5. #5
    Master OptiBoarder Darryl Meister's Avatar
    Join Date
    May 2000
    Location
    Kansas City, Kansas, United States
    Occupation
    Lens Manufacturer
    Posts
    3,700
    I have an article on prism-thinning available online: Prism-Thinning Progressive Lenses. It might provide some useful pointers for you.
    Darryl J. Meister, ABOM

  6. #6
    OptiBoard Apprentice
    Join Date
    Oct 2020
    Location
    India
    Occupation
    Optical Laboratory Technician
    Posts
    24
    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.

  7. #7
    OptiWizard
    Join Date
    Jul 2016
    Location
    California
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    392
    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.

  8. #8
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
    Join Date
    Oct 2016
    Location
    Maryland
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    1,198
    Quote Originally Posted by shubhendu View Post
    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.
    I bend light. That is what I do.

  9. #9
    OptiBoard Apprentice
    Join Date
    Oct 2020
    Location
    India
    Occupation
    Optical Laboratory Technician
    Posts
    24
    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.?

  10. #10
    OptiWizard
    Join Date
    Jul 2016
    Location
    California
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    392
    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.

  11. #11
    OptiBoard Apprentice
    Join Date
    Oct 2020
    Location
    India
    Occupation
    Optical Laboratory Technician
    Posts
    24
    Ok..thanks

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Fitting PALs with prescribed prism
    By Joann Raytar in forum Ophthalmic Optics
    Replies: 6
    Last Post: 10-28-2006, 01:00 PM
  2. Prism Thinning?
    By bser in forum General Optics and Eyecare Discussion Forum
    Replies: 7
    Last Post: 11-30-2005, 07:43 AM
  3. Prism Thinning problems
    By Rafael in forum General Optics and Eyecare Discussion Forum
    Replies: 3
    Last Post: 09-02-2005, 11:04 PM
  4. Matching Prism Thinning
    By RREADER in forum General Optics and Eyecare Discussion Forum
    Replies: 8
    Last Post: 11-18-2001, 10:00 AM
  5. Equithin/ Prism Thinning
    By Mikol in forum Ophthalmic Optics
    Replies: 9
    Last Post: 07-10-2001, 02:34 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •