Results 1 to 3 of 3

Thread: Progressive Lenes and the Lensometer

  1. #1
    OptiBoard Novice
    Join Date
    Jul 2015
    Location
    Florida
    Occupation
    Dispensing Optician
    Posts
    1

    Progressive Lenses and the Lensometer

    Hopefully someone can educate me on this issue.
    When I neutralize some progressive lenses through the distance reference point the mires are quite often fuzzy (usually plus powers). If I insert a 3^ axillary prism the mires tend to become clear. We use mostly Hoya products, but this occurs with others as well.

    Thanks and please forgive my lack of knowledge.
    Last edited by William LDO; 07-15-2015 at 04:45 PM. Reason: spelling

  2. #2
    Master OptiBoarder MakeOptics's Avatar
    Join Date
    Aug 2011
    Location
    none
    Occupation
    Other Eyecare-Related Field
    Posts
    1,327
    Quote Originally Posted by William LDO View Post
    Hopefully someone can educate me on this issue.
    When I neutralize some progressive lenses through the distance reference point the mires are quite often fuzzy (usually plus powers). If I insert a 3^ axillary prism the mires tend to become clear. We use mostly Hoya products, but this occurs with others as well.

    Thanks and please forgive my lack of knowledge.
    Chromatic Aberration, you effectively neutralize it when you place your prism in the lensmeter. If the lens has no prism thinning the the optical center is ground at the prism reference point, if your progressive is on average 4mm above this point at fit and the distance reference point is another 3mm to 4mm above that point, then you are a total of 7mm to 8mm off axis and will experience some prism. If prism thinning is included again using some assumptions lets say a 2.00 add, the amount of prism thinning is going to be roughly 2/3 or 1.33^D and the orientation is going to be base down, on a plus lens you are going to be 7mm to 8mm off axis and add that additional 1.33^D you would compound the issue.
    http://www.opticians.cc

    Creator of the industries 1st HTML5 Browser based tracer software.
    Creator of the industries 1st Mac tracer software.
    Creator of the industries 1st Linux tracer software.

  3. #3
    Master OptiBoarder optical24/7's Avatar
    Join Date
    May 2006
    Location
    Down on the Farm
    Occupation
    Dispensing Optician
    Posts
    5,627
    Quote Originally Posted by MakeOptics View Post
    Chromatic Aberration, you effectively neutralize it when you place your prism in the lensmeter. If the lens has no prism thinning the the optical center is ground at the prism reference point, if your progressive is on average 4mm above this point at fit and the distance reference point is another 3mm to 4mm above that point, then you are a total of 7mm to 8mm off axis and will experience some prism. If prism thinning is included again using some assumptions lets say a 2.00 add, the amount of prism thinning is going to be roughly 2/3 or 1.33^D and the orientation is going to be base down, on a plus lens you are going to be 7mm to 8mm off axis and add that additional 1.33^D you would compound the issue.
    MO, specifically, isn't is LCA's (prism and abbe) that you are referring to?

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Shooting Lenes....HELP!
    By CaOpticalGoddess in forum General Optics and Eyecare Discussion Forum
    Replies: 28
    Last Post: 04-23-2008, 06:54 AM
  2. simi finished lenes..........
    By eyesonyou in forum Optical Marketplace
    Replies: 0
    Last Post: 01-03-2007, 03:46 PM
  3. transition type lenes
    By markssunwear in forum Optical Marketplace
    Replies: 0
    Last Post: 11-01-2006, 10:16 AM
  4. Optical lenes...
    By markssunwear in forum General Optics and Eyecare Discussion Forum
    Replies: 2
    Last Post: 07-24-2006, 11:07 PM

Tags for this Thread

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
  •