Should Mono or Binocular PD'd Be taken on Single Vision & Bifocal lenses??

[Trevor D]

Not to say that you don't, but make sure you mark the OC on their existing pair and proceed cautiously if there is a big difference. Sometimes doing the right thing will burn you because of a previous dispenser.

So in this case do you:

Go with your new (correct) measurement?

Use the same as their old pair anyway?

Take an average between the two?

:idea:

[Jedi]

So in this case do you:

Go with your new (correct) measurement?

Use the same as their old pair anyway?

Take an average between the two?

:idea:

It's funny that you ask, I started a thread along those lines a couple weeks ago, here

[sharon m./ aboc]

I disagree that it's not noticeable to have a binocular PD's on flat top lenses. I think a 2mm difference is quite noticeable in a flat-top after it is mounted in the frame. In the two optical shops I have worked in previously there wasn't even an option for moncular PD's in Flat Tops.....You had to take the total Pd an divide it by 2. I say binocular for all Flat Tops and mono for everything else, especially PAL's. I also take Ocular Centers for all Single Vision It's especially important on high cyl's.

[Jedi]

You in business to provide the best visual results or the best cosmetic results?

Sharon, I think Chip summed things up pretty well with this quote. If your client/office are more concerned with cosmetic what are they doing with FT's in the first place?

[coda]

Originally Posted by chip anderson
You in business to provide the best visual results or the best cosmetic results?

Sharon, I think Chip summed things up pretty well with this quote. If your client/office are more concerned with cosmetic what are they doing with FT's in the first place?

I should preface this by saying I'm not an optician nor am I involved with the dispensing of eyeglasses or vision correction of any type.

If the vision correction is perfect but the patient feels that the glasses make them so unattractive that they don't wear them then you've accomplished nothing. The more rational approach (and incidentally the middle ground) is to discuss with the patient the various liabilities of lens placement in the frame vis-a-vis cosmetic appearance and optical performance.

Incidentally, I'd bet you're actually in business primarily to make money; then secondarily to make your patients happy.

[Jedi]

Incidentally, I'd bet you're actually in business primarily to make money; then secondarily to make your patients happy.

That's why I would dispense a progressive if a clients main concern was cosmetics.
:D

Coda, you do bring up a rational way of dealing with these situations, but I would hope most opticians stress optics versus "looks". AR coatings, round segs, fused glass segments are all potential solutions for a clients with dissimilar segs that are concerned with cosmetics. They are virtually indetectable and maintain proper optical properties.

[sharon m./ aboc]

Coda and Jedi, I see what you both mean about flat-tops being so unattractive to begin with that if a person wears a flat top they can't possibly be concerned enough with aesthics to care if they are symetrical in the frames. I think A/R would help, but I'm still going to do the binocular PD on flat tops and I wouldn't dream of putting a die hard life- time flat top customer in a progressive. Thanks for your input any way....... .ENGINEER CODA: In response to your:" I'D BET YOU'RE IN BUISINESS PRIMARILY TO MAKE MONEY:SECONDARILY TO MAKE YOUR PATIENTS HAPPY." OUCH!!!!. Nothing could be further from the truth. I am an hourly employee at Costco. I don't work on a commission. I didn't really think you were a train engineer. (HA!) What exactly are the 3 O's you speak of?

[coda]

Coda and Jedi, I see what you both mean about flat-tops being so unattractive to begin with that if a person wears a flat top they can't possibly be concerned enough with aesthics to care if they are symetrical in the frames. I think A/R would help, but I'm still going to do the binocular PD on flat tops and I wouldn't dream of putting a die hard life- time flat top customer in a progressive. Thanks for your input any way....... .ENGINEER CODA: In response to your:" I'D BET YOU'RE IN BUISINESS PRIMARILY TO MAKE MONEY:SECONDARILY TO MAKE YOUR PATIENTS HAPPY." OUCH!!!!. Nothing could be further from the truth. I am an hourly employee at Costco. I don't work on a commission. I didn't really think you were a train engineer. (HA!) What exactly are the 3 O's you speak of?

Actually, I don't think flat tops are unattractive, I was really just trying to point out that the placement of the lens in the frame needs to address both cosmetic and optical performance. I like flat tops though I'm still a few years away from needing them (I hope). The 'primarily to make money' wasn't a dig, who among us would go to work every day (or at least our current jobs) if we didn't need the money?

The three O's are: Opticians, Ophthalmologists and Optometrists (in no particular order).

There are a lot of days when I think I'd rather be a train engineer. See the country, be hundreds or even thousands of miles away from your boss, deal with a very, very limited numbers of coworkers. What could be better? :D

Oh, and Jedi, I hope you're right. When I go to get glasses I want the person behind the counter looking out for my vision over my appearance; but then I'm a nerd and we don't care about how we look, right? :D :D

[Rockstargazer]

In the old days before pupillometers, there were PD rulers. PD rulers don't take a mono pd, BUT, a good optician would (I did) observe the patients face, especially how the eyes were placed in the head. Was one eye further away from the nose than the other? Was one eye higher or lower (personal choice) than the other? The next step would be to check the patients pd in their current glasses. Hmm If the pd measured different in the glasses than what your measurement was, what do you do? Anyone ever take a vertex measurement?

My point is this- the human visual system is remarkably relilient but very unique to the individual and a "one size fits all" approach to measuring PD's or seg heights is not going to work every time. Carpenters have a motto: "Measure twice, cut once." Wouldn't you and/or your boss rather a thorough job is done before the glasses are made? Hate those redo's..........

Just my two cents worth.

[QDO1]

I specify mono PD's, heights, frontal angle, bow, LTB, TW and BVD. Obvoiusly I adjust the heights to compensate for the frontal angle, and the RX for BVD, FA and bow. If you can do a job better, then thats the way to do it

By the way, youwill be surprised how many patients mention they have never been measured up like that before

It is good practice to do this for all dispenses, in that way when a really awkward one comes your way, you find taking the measurments second nature, and your patient will feel confident in you

On the other side of the coin.. i was asked by a OMP (UK for Eye Doctor) to dispense his own lenses, with a script of R-4.00 - 1.00 @ 47.5. He asked me to glaze -4.00DS. I queried this, and was informed "Cyls Distort!" so I asked him if he prefered the best sphere of -4.50... "Nope -4.00 please" god help us all

[QDO1]

I'm unconvinced. I maintain that monocular PDs are unessecary for SV glasses since even if the optical centers do not match up with the pupil centers, all you have is a mild yolked prism. No big deal. No diminished clarity. No discomfort. No need to break out the Essilor freebie pupillometer.

Some food for thought

The optical performance of a lens reduces as you move away from the optical of the lens. This is true for most of the optical abberations, and the higher the prescription, the worse the error:

Off axis lenses exhibit:

Increased power errors (e.g. oblique astigmatism)
Increased chromattic abberation (TCA)
Increased spherical aberration

Encreased effect from curvature of field

More coma


This can be demonstrated by doing some contrast sensitivity tests

Yes we can be sensible and brush over the above if it is insignificant to the patient, but overall we can not just pretend the laws of optics dont exist

I was taught the effective useful area on a lens (as a rule of thumb) in CM is 10/RX. in a patient of +10.00D the useful area of the lens is a 1 CM circle. On that basis it doesnt take too much to extrapolate that the useful temporal area is reduced by about 20% if the centres are offset 1mm in.

It becomes really interesting to use the same phlosophy, and map a patient's binocular zone of useful vision with oblique astigmatism, (draw an elipse to show the right eyes useful zone of vision on top of the elipse for the left eye), all of a sudden we find the area can become really small with a moderate RX. Thats why the young ones measure everything