Results 1 to 14 of 14

Thread: compensating Rx for Vertex difference

  1. #1
    OptiBoardaholic Randle Tibbs, ABOM's Avatar
    Join Date
    Dec 2012
    Location
    Alabaster, AL
    Occupation
    Other Eyecare-Related Field
    Posts
    211

    compensating Rx for Vertex difference

    Curious as to how many out there compensate Rx's when there is a difference from the refracted VD to the fitted VD

  2. #2
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    8,182
    Only in really high cases, like +/- 7 or 8.

    I refract at 14 (I think) and if you fit glasses properly you'll be OK.

    It's the weird combos like..."I want to wear my glasses---here!" and a -8.00 that will get my calculator going. Even so, how do you accurately measure frame vertex without a special device that no one will give me for free?

  3. #3
    OptiBoardaholic Randle Tibbs, ABOM's Avatar
    Join Date
    Dec 2012
    Location
    Alabaster, AL
    Occupation
    Other Eyecare-Related Field
    Posts
    211
    the patient i have is OD -12.00-1.75 OS -18.25-1.75 refracted at 12mm fitted glasses at 18mm measured with a distometer. weird i know, but it caused me to wonder how many opticians would actually compensate it.

  4. #4
    Master OptiBoarder
    Join Date
    Feb 2013
    Location
    PA
    Occupation
    Dispensing Optician
    Posts
    1,365
    most doctors won't tell you what the refracting vertex is on the rx, so you pretty much have to play a guessing game. I would say in most cases you're ok, but if you note the fitting is not "standard" and looks unusual, you're best to compensate for it. That rx that you had would be the type of Rx you'd want to. I'm with DrK... high Rx yes, but only if the fitting is really different.

  5. #5
    OptiBoard Apprentice
    Join Date
    Jan 2020
    Location
    Minneapolis
    Occupation
    Optical Laboratory Technician
    Posts
    19
    The problem is the wearing vertex is seldom known until lenses are made. Using a distometer on sample lenses will give you poor results. Or am I missing something?

  6. #6
    OptiBoard Professional
    Join Date
    Jul 2016
    Location
    California
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    130
    Measurements can be made by placing a piece of tape across the back of the frame and measuring from a closed eye lid to the tape. Then you add approximately 3mm for the thickness of the lid and add the vertex depth of the back curve which you can easily calculate. Glasses move on the patient face so trying to do this on moderate rx’s is time not well spent.
    In years gone by when there were no implants and eyeglass lenses were made above +10.00 for those post cataract patients this was a common practice.

  7. #7
    OptiBoard Apprentice
    Join Date
    Jan 2020
    Location
    Minneapolis
    Occupation
    Optical Laboratory Technician
    Posts
    19
    Lensman11, Thanks for that advice

  8. #8
    OptiBoardaholic Randle Tibbs, ABOM's Avatar
    Join Date
    Dec 2012
    Location
    Alabaster, AL
    Occupation
    Other Eyecare-Related Field
    Posts
    211
    Quote Originally Posted by Lensman11 View Post
    Measurements can be made by placing a piece of tape across the back of the frame and measuring from a closed eye lid to the tape. Then you add approximately 3mm for the thickness of the lid and add the vertex depth of the back curve which you can easily calculate. Glasses move on the patient face so trying to do this on moderate rx’s is time not well spent.
    In years gone by when there were no implants and eyeglass lenses were made above +10.00 for those post cataract patients this was a common practice.
    I was fitting cataract pts back in the 80's at an eye hospital where we were fitting 15 -18 pair per day and we would be given the RVD.

  9. #9
    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
    Join Date
    May 2000
    Location
    Seaford, NY USA
    Occupation
    Dispensing Optician
    Posts
    5,859
    Quote Originally Posted by Lensman11 View Post
    Measurements can be made by placing a piece of tape across the back of the frame and measuring from a closed eye lid to the tape. Then you add approximately 3mm for the thickness of the lid and add the vertex depth of the back curve which you can easily calculate. Glasses move on the patient face so trying to do this on moderate rx’s is time not well spent.
    In years gone by when there were no implants and eyeglass lenses were made above +10.00 for those post cataract patients this was a common practice.
    I think the allowance for lid thickness is typically 1mm.

    B

  10. #10
    OptiBoardaholic Randle Tibbs, ABOM's Avatar
    Join Date
    Dec 2012
    Location
    Alabaster, AL
    Occupation
    Other Eyecare-Related Field
    Posts
    211
    +1

  11. #11
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    5,124
    Quote Originally Posted by Randle Tibbs, ABOM View Post
    the patient i have is OD -12.00-1.75 OS -18.25-1.75 refracted at 12mm fitted glasses at 18mm measured with a distometer. weird i know, but it caused me to wonder how many opticians would actually compensate it.
    Hard to understand how the refractor head can sit that much closer than the frame. Might be a good idea to refract over the old Rx to see what's what.

    Best regards,

    Robert Martellaro
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    Science is a way of trying not to fool yourself. - Richard P. Feynman

    It is easier to fool a man, than to convince a man he has been fooled. -Mark Twain

  12. #12
    Master OptiBoarder OptiBoard Silver Supporter
    Join Date
    Jul 2002
    Location
    Vancouver, BC CANADA
    Occupation
    Dispensing Optician
    Posts
    1,119
    Quote Originally Posted by Randle Tibbs, ABOM View Post
    the patient i have is OD -12.00-1.75 OS -18.25-1.75 refracted at 12mm fitted glasses at 18mm measured with a distometer. weird i know, but it caused me to wonder how many opticians would actually compensate it.
    The wheel calculator that comes with a distometer would show a 6mm compensated Rx increase for OD of about -1.00 at -12.00 and over -2.00 increase in OS for -18.00, so yes... a qualified optician must compensate for a 6mm VD change in this high Rx.
    And this patient didn't wake up with a -12.00 and -18.00 RX, so consider using his old glasses for a vertex distance measurement and add 1mm for thickness of eyelid. Every optical should have a distometer.

  13. #13
    Master OptiBoarder OptiBoard Silver Supporter
    Join Date
    Feb 2016
    Location
    usa
    Occupation
    Dispensing Optician
    Posts
    625
    Quote Originally Posted by tmorse View Post
    The wheel calculator that comes with a distometer would show a 6mm compensated Rx increase for OD of about -1.00 at -12.00 and over -2.00 increase in OS for -18.00, so yes... a qualified optician must compensate for a 6mm VD change in this high Rx.
    And this patient didn't wake up with a -12.00 and -18.00 RX, so consider using his old glasses for a vertex distance measurement and add 1mm for thickness of eyelid. Every optical should have a distometer.
    Agreed. I don't know how anyone could have a chance of making successful glasses for this Rx without doing this.

  14. #14
    OptiBoardaholic Randle Tibbs, ABOM's Avatar
    Join Date
    Dec 2012
    Location
    Alabaster, AL
    Occupation
    Other Eyecare-Related Field
    Posts
    211
    i agree with all that has been said. Mainly, I was just curious to how many opticians still remember how to and why to calculate the effective power and when to do so. Also, you'd be surprised how many do not know what a distometer is or how to use the compensating wheel or that you also need to calculate for the cyl as well.
    really wasn't expecting this much response, but glad to see it.
    thank you all.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Vertex vs. Fitting
    By Judy Canty in forum Ophthalmic Optics
    Replies: 7
    Last Post: 04-06-2011, 06:13 PM
  2. compensating prism using dissimilar segs
    By mtillman in forum Ophthalmic Optics
    Replies: 8
    Last Post: 04-09-2008, 08:31 PM
  3. Looking for Marco or Topcon Lensmeter with Prism Compensating Device
    By snowmonster in forum Optical Marketplace
    Replies: 2
    Last Post: 03-30-2007, 12:41 PM
  4. Vertex Compensation!
    By RNPSRJ in forum General Optics and Eyecare Discussion Forum
    Replies: 4
    Last Post: 03-23-2007, 04:25 PM
  5. Compensating for vertex distance
    By Neophyte Optician in forum Ophthalmic Optics
    Replies: 2
    Last Post: 05-20-2005, 03:31 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
  •  
OptiBoard is proudly sponsored by:
Younger Optics and Vision Equipment