Results 1 to 5 of 5

Thread: Question about PD for intermediate glasses

  1. #1
    OptiBoard Novice
    Join Date
    Jun 2020
    Washington, DC
    Other Eyecare-Related Field

    Question about PD for intermediate glasses

    I'm not an eyecare professional, so I hope it's OK that I post here. I saw some posts by people who weren't eyecare professionals, but those were from some time ago, and I noticed when registering that you ask that only eyecare professionals register. But on the other hand, you have a subforum intended for professionals only, so I thought elsewhere in the forum might be OK for non-professionals.

    I have a question, as a patient, about pupillary distance for intermediate glasses (myopia, presbyopia).

    My optometrist doesn't record PD, and my last optician visit was long ago and they no longer have me on file. I'm ordering glasses online while quarantining, so am avoiding going in person to measure PD. I measured Dist PD myself using this method and found it to be 64mm.

    My question is: should I adjust Dist PD for these intermediate glasses?

    I read one source that says Dist PD is used for both distance and intermediate and Near PD is used for near. Conversely, the online store I'm ordering from advised me they use Near PD for intermediate.

    I know there's a formula (and tables, as well as a rule of thumb where you subtract 3mm from Dist PD) to calculate PD for a given working distance, from a measured Dist PD ("System for Ophthalmic Dispensing" 3rd Ed. p.32, image from Amazon preview):
    Click image for larger version. 

Name:	CROPPED - FireShot Capture 4159 - System for Ophthalmic Dispensing_ 9780750674805_ Medicine & He.jpg 
Views:	7 
Size:	25.9 KB 
ID:	14703
    I found that the Optiboard members, drk and HarryChiling, expressed it in this form:
    Near PD = [Distance PD mm * (10 * Reading Distance cm)] / [(10 * Reading Distance cm) + 27]
    NPD / WD = DPD / (WD + CTR)

    I sit between 19" and 32" from the screen, usually between 24" and 32", and less often at 19". My optometrist kindly provided new adjusted prescriptions (without PD) for 19" and 32" working distances (using my existing unadjusted prescription on file with ADD power):

       Sphere  Cylinder  Axis
    OD -5.50   -0.50     125
    OS -4.75   -0.75     055
    Notes: computer dist 19 inches away
       Sphere  Cylinder  Axis
    OD -6.00   -0.50     125
    OS -5.25   -0.75     055
    Notes: computer dist at 36 inches away
    Using the formula above for PD, I found my PD for 19" WD would be 60.6 mm, PD for 24" WD would be 61.3mm, PD for 32" WD would be 62.0mm (with Dist PD = 64mm).

    I'll probably use, and submit to the store, the SPH and prescription for 19" WD.

    But should I submit one of those PD's adjusted for intermediate working distances, or should I avoid adjusting the PD and submit a PD closer to the Dist PD, for versatility's sake?

    Although the SPH of the glasses will be optimized probably for a WD of 19", I'm hoping to use the glasses for multiple distances around the house during quarantine: perfect intermediate vision, OK near vision, OK (imperfect) distance vision (just around the house, no driving). I have a 35-yr-old pair of broken single-vision distance glasses which does all those things surprisingly well, while using Dist PD as its PD. So I wonder if it's possible to duplicate this with the new glasses, and if one of the ways to do so is to set Dist PD as the PD.

    The 35-yr-old glasses seem similar to what the new intermediate glasses would be (single-vision distance glasses with not-strong-enough distance prescription) and also are similar in the way I'd use them (for multiple distances around the house).

    I consider my presbyopia less forgiving, so want the SPH to accommodate the presbyopia. But the PD issue seems more forgiving: it strikes me that everyone's single-vision distance glasses uses Dist PD as PD, and everyone wears them for all distances from infinity to near with no PD issues. So maybe using Dist PD as PD is the more "natural" or better way, if the glasses are going to be used for multiple distances around the house like with my old glasses, which used Dist PD as PD? Or, is this incorrect?

    If simply using Dist PD (64mm) for the PD isn't advised, I could split the difference and use 63mm (optimal for 67" WD) or 62mm (optimal for 32" WD). To me, using 61mm (a full 3mm less than the Dist PD) for the PD seems extreme if I hope to use the glasses at multiple distances, and because my old glasses which worked at multiple distances used Dist PD. But I might be understanding this wrong.

    I understand if the glasses truly are meant to be single-purpose, for only a 19" working distance, then there's no reason not to set PD for that distance. But my old glasses seem to suggest the new glasses can work at multiple distances, and if the eye can tolerate (or if the eye is used to?) the glasses' PD being set to Dist PD even when the eye is looking at near or intermediate objects, is it more natural or better to set Dist PD as PD? Or not?

    Definitely welcome people's advice or opinions on this.

    I should say that computer distance is still the first priority, so if PD needs to be set to computer distance for computer distance to work well, I'll do it, but I got an impression from my old glasses that PD doesn't need to be set to the specific distance.

    I read that ANSI tolerance for PD in single vision glasses is 2.5mm, but don't know if I understand this correctly and also read some people consider 2mm to be significant.

    Thank so much.
    Last edited by Jmcyang; 06-17-2020 at 05:59 AM.

  2. #2
    Master OptiBoarder
    Join Date
    Jun 2012
    Mitten State
    Ophthalmic Technician
    This entire forum is for eyecare professionals only. Sorry.

  3. #3
    Master OptiBoarder AngeHamm's Avatar
    Join Date
    Apr 2010
    Richmond, VA
    Optical Retail
    You should talk with an optician.
    I'm Andrew Hamm and I approve this message.

  4. #4
    What's up? drk's Avatar
    Join Date
    Mar 2004
    You're clearly quite intelligent and honest. But you have to understand that a responsible forum isn't going to allow you to strike up a pro-bono client/professional relationship. It'd likewise be unprofessional for you to log on to an M.D. forum and ask what dosage of meds that you should buy on the internet.

    Just because the internet allows you access to professional dicussions, professionals are still bound by ethics to not give bad or wrong advice, and good opticianry cannot be conducted online.

    So, being an intelligent person, you should see what is trying to be preserved here: good, responsible, optical care. That's what this website is dedicated to; specifically, sharing information and knowledge amongst colleagues. This is not a self-help forum, nor a forum to help you to do your own opticianry.

    No hard feelings, and I'm sure you appreciate the candor.
    Last edited by drk; 06-17-2020 at 09:49 AM.

  5. #5
    Forever Liz's Dad Steve Machol's Avatar
    Join Date
    Apr 2000
    Back in AZ
    Other Eyecare-Related Field
    As per the forum rules you agreed to when you registered:

    "This forum is for Eyecare Professionals. Consumers are not allowed to post on the Board, although they can read posts and search topics."

    All the professional Opticians on this site would love to help you solve your problems or answer your questions about your eye care and eye wear need! But vision and visual solutions can have thousands of correct as well as incorrect answers.

    OptiBoard Administrator
    OptiBoard has been proudly serving the Eyecare Community since 1995.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Intermediate formula question
    By CatwithGlasses in forum General Optics and Eyecare Discussion Forum
    Replies: 26
    Last Post: 11-23-2015, 03:12 PM
  2. Intermediate Question
    By PartTimer in forum Progressive Lens Discussion Forum
    Replies: 14
    Last Post: 07-10-2012, 09:46 PM
  3. intermediate pal (access) or short corridor with intermediate at top
    By tolpuppy in forum Progressive Lens Discussion Forum
    Replies: 7
    Last Post: 08-27-2010, 12:41 PM
  4. Shamir Intermediate Channel Question
    By john-atlanta in forum Progressive Lens Discussion Forum
    Replies: 9
    Last Post: 07-26-2009, 10:58 PM
  5. Question on glasses
    By lassa in forum General Optics and Eyecare Discussion Forum
    Replies: 6
    Last Post: 05-13-2005, 03:59 PM

Tags for this Thread


Posting Permissions

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