PD: Round up or Down on .5 pd when not available?

[emsees]

Greetings,

Well I think the subject says it all.. but in the case of a .5 PD
measurement, which is better to do when the place doesn't do .5 pd
gradients? Round up or down?

In my case, the PD measurement was given as:

PD Distance:33.5 Near: 30.0 63.5

And, if it matters, I'm nearsighted.

I'm _probably_ ordering from Zenni, and they don't seem to give the .
5's as options.

thanks.

[deborah]

I would round up, then explain more fully in the comments section. I
think that would take care of it.

[Ira Mitchell]

That seems like excellent advice.
-Ira

[Fred Di]

NOT so fast, if your Dr wrote down what you said

PD Distance:33.5 Near: 30.0 63.5

I have no idea what that means.

Is the Distance PD 33.5 for each eye, thus 67mm total
and the Near PD 30 x 2 or 60

Where did the 63.5 come from is that actually written on the script,
or did you just add them.

You would never add the distance and nearr PD's.

And your PD can't be 33.5 unless you are a very small child.

> > > thanks.- Hide quoted text -
>
> - Show quoted text -

[Chuck Knight]

I've helped a number of people with ordering from Zenni, and I always choose the closest value from the menu, and explain in the comments section during checkout.  I've seen weird 1/8 diopter corections, fractional mm on PD measurements, etc.

I do, though, agree with Fred.  Those PD numbers are gibberish, unless your doctor assumed you are perfectly symmetrical.  Which, almost noone is.  If he gave you a monocular PD, there should have been 2 sets of numbers.  OS near and OS far, then OD near and OD far.  (doctor talk for left and right eye)  If that's your binocular PD, then your head is abnormally tiny.  The average PD for an adult is somewhere in the neighborhood of 60mm.

You should call your doctor and get him/her to explain those PD numbers.  OR, you could pop into any optical dispensary and be measured.  Many on this list do it themselves, but I still prefer the use of a professional for such things.  The cost should be negligible, if they even charge you at all.

     -- Chuck Knight


.

[emsees]

Chuck Knight wrote:
> I've helped a number of people with ordering from Zenni, and I always choose
> the closest value from the menu,

So that was my question. Round up or down? Since .5 is equidistant
between two integers. (Obviously someone else already said round
up. . but that may not be consensus.)

> I do, though, agree with Fred. Those PD numbers are gibberish, unless your
> doctor assumed you are perfectly symmetrical. Which, almost noone is. If
> he gave you a monocular PD, there should have been 2 sets of numbers. OS
> near and OS far, then OD near and OD far. (doctor talk for left and right
> eye) If that's your binocular PD, then your head is abnormally tiny. The
> average PD for an adult is somewhere in the neighborhood of 60mm.

I got the numbers from America's Best (where i got my initial script.)
They _hadn't_ measured it initially. I had to go in and get them to
take it (which they did, only with one of those mechanical binocular
things.) I got the impression they were not too excited about
measuring and providing it, so I just went with what they wrote.

I couldn't get walmart to do it as suggested on the other posts.

I tried to do it myself with the ruler thing.. but then I realized
that the two different rulers I had were different from each other and
thus not reliable. Before I realized this, I thought my number was
something like 62, so I figured the 63.5 was close and thus probably
accurate.

thanks
--
EM

[Paul]

I don't think it matters too much if you round up or down.

And it seems like the optician at America's Best didn't give you
enough information. You might simply want to buy a good ruler and take
your own measurements, unless you can find somewhere else where
they'll measure it.

[Chuck Knight]

That's precisely my point.  They should be going off the information in your COMMENTS section, instead of what you enter on the form.  And, frankly, a 0.5mm error wouldn't be bad, anyway.  I would round up, myself, because those gadgets measure at what doctors refer to as "optical infinity" and that usually works out to around 20 feet.  I found that rounding my own value up, makes the glasses MUCH more comfortable.

But, seriously, those PD numbers that they gave you don't make a lot of sense.

If it was me, I'd just run to a WalMart (yes, I know) or some other dispensary, and show them your prescription.  Ask them your question...but word it carefully.

Look around the dispensary at various frames.  When the saleslady comes over to help, say something like this:

Oh, no thanks...I'm just looking around.  Yeah, I'm in the market for a new pair of glasses...just got a new prescription.  Wait a second!  Maybe you *could* help me.

(Reach in pocket or purse, and extract rx) 

My eye doctor just gave me this prescription, and this part jumped out at me...just doesn't look right.  (point at the number)  I looked it up on the internet, and PD tells how far apart my eyes are...right?  So, is this supposed to mean that my eyes are only 30mm apart?  That's only about this big...  (hold fingers just over an inch apart)

(you'll probably get an explanation of monocular and binocular PD values)

But, wouldn't it have to say which number was right, and which number was left?  Yeah, I don't see it either.

Say, do you have one of those binocular gizmos?  Could I just pay you to measure it for me, again?  It never hurts to confirm the number, right?

     -- Chuck Knight

[deborah]

Costco or Sam's optical will measure for you if you just ask them.
You don't have to belong to either of these stores to visit the
optical shop. When you go in, you just tell the person checking cards
that you are just in to visit the optical department, and they will
let you right in.

Also, most any optical shop in a store will do this measurement if you
ask them. Wal-Mart or Target or anywhere else will probably do it for
you.

Just say something like, "Would you please do me a favor? I need to
have my correct PD measurement. Would you measure me?" Mostly these
folks are happy to help if you ask nicely. Give it a try.

[Chuck Knight]

A thought -- is this your first pair of glasses?  If not, go to your previous dispensary and ask for a printout of your records.  The PD is part of your record...they may even give that part over the phone.

Your PD doesn't change, unless you're still growing, or something extraordinary is happening.

     -- Chuck Knight

[Ev]

My PD is 66 but it breaks down as 32.5 and 33.5, reading 30.5 and
31.5. Apparently one eye is a mm closer to my nose than the other -
who knew?. I always put the 66 in the PD space but in the notes
section I give the specific right and left numbers - As far as I can
tell, they've always done it correctly.

It was walmart that measured my PD this accurately when I had a pair
made there some years ago and they provided the numbers to me when I
phoned.

On Aug 23, 12:36 am, "Chuck Knight" <chuckkni...@gmail.com> wrote:
> A thought -- is this your first pair of glasses?  If not, go to your
> previous dispensary and ask for a printout of your records.  The PD is part
> of your record...they may even give that part over the phone.
>
> Your PD doesn't change, unless you're still growing, or something
> extraordinary is happening.
>
>      -- Chuck Knight
>

[The Big Bad]

It seems as if 39dollarglasses is the only place where you can order
a .5 PD directly on their drop down menus. Can that be right?

For the other sites, do they actually adjust the PD based on the
comments section? Ex., will selecting 63 PD then indicating that the
PD should actually be 63.5 work in practice?

[onlineIDoc]

its hard to grind these things even near the .5 mark anyway, you're
lucky when most progressives come in near the mm, so seeing the
process in reverse, I guess they round(up).