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

**eyesonu38** · 08-23-2005, 07:51 PM

I have been an Optician for over 20 years. Some of the newer Opticians in my office are taking mono pd's on Flat Top and single vision lenses. I have only taken mono pd's on progressive lenses. My argument was the Ft segs will be off and look bad. What do you do in your offices??

**chip anderson** · 08-23-2005, 07:58 PM

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

**ldyflsh** · 08-23-2005, 08:07 PM

I take mono pd's on ALL patients. I'm after the best visual correction for the patient. I also take the time to explain to my patients that because each eye is different, the measurements are taken to assure their best correction:)

**For-Life** · 08-23-2005, 08:37 PM

no one takes mono pds for single vision, bifocals (and in a lot of cases PALs). So if you do you might improve the vision and make it slightly crisper. The competitors will not do that.

As for the segs not matching, a seg being 2mm moved in on one side will not be noticed.

**Happylady** · 08-23-2005, 09:26 PM

I always take mono pd's on single vision and progressives. I generally don't on bifocals.

**JennyP** · 08-23-2005, 10:13 PM

Originally Posted by For-Life

no one takes mono pds for single vision

We do at LC, for polycarb.... our software won't let us do otherwise. :p
If you're using a pupilometer, why not?

**For-Life** · 08-23-2005, 10:28 PM

Originally Posted by JennyP

We do at LC, for polycarb.... our software won't let us do otherwise. :p
If you're using a pupilometer, why not?

Most I talk to just do not believe in it and people tend to get lazy and not take the extra step. Even if it asks you to do it monocularly a lot of people I talk to just divide the biocular by 2.

**CME4SPECS** · 08-23-2005, 10:46 PM

Why wouldn't you take a mono PD? If you are using a pupilometer, you have the mono measurements, why not use them? And you should take mono seg heights too. I had a man in this morning, he ordered FT 35, his Pd is 34/32 and 30/28 the seg height was 20 and 17. You bet that's the way I'm going to make his glasses! His old lenses were FT 28 made to binocular PD and seg height. He complained about seeing the line with his left eye but not the right, and that he had a larger field with his right eye. He knows that the segs are not going to be in the same spot in the frame, but, will line up properly with his eyes. He says he can understand since he had his face practically ripped off in an accident a few years ago.
He's going to be a happy camper when he gets his new glasses tomorrow!

**optoblog.com** · 08-24-2005, 01:16 AM

I think it's important to educate the optical client about why the lined bifocals will be "off center" (or whatever comforting terminology you use) so that they won't come back to the doctor and say, "They made my glasses wrong. See, one line is closer to the edge than the other!"

Someone please explain the necessity for taking monocular p.d.'s on a single vision Rx.

**Chris Ryser** · 08-24-2005, 05:12 AM

Actually a very simple explanation for every case.......................

If you rake a monocular PD and mount the lenses accordingly ........even slightly off center.............the patient will look exactly through the optical center and the segments placed at the exact spot. Tha applies for all types of lenses, with the exception when prismatic effects are required.

**optoblog.com** · 08-24-2005, 02:41 PM

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.

**coda** · 08-24-2005, 06:23 PM

Originally Posted by optoblog.com

Don't ask what you can do. DO what you can do. -My Paternal Grandpa

Hmmm, so does this mean you can't take mono pds because otherwise you'd be doing it? ;)

(no offense intended, it was just funny to see that tag line at the end of your post)

**mshimp** · 08-24-2005, 07:21 PM

For regular sv good old binocular pd works fine.If your using an aspheric sv use mono pds and pupil heights.for line fts and trifocals always use binocular pd for near decentration ,and for the distance (if you are an extreme perfectionist)use monocular pds. I would only do this with higher powers.Progressives always use mono pds and pupil heights.Since we're talking about moncular pds,do you ever experience errors using a pupilometer that you know is perfectly calibrated but indicates incorrect pds?

**Specs** · 08-24-2005, 08:19 PM

On SV lenses, taking/using mono PD's comes down to the power of the lens and the resultant prismatic effect by not doing it monocularly. Easier to just use the patients actual PD rather than figuring out the power in the 180 meridian. In bifocals it can matter as far as the prism issue, but also the eye should be centered on the seg at near focus to insure the widest near vision area.

**Jedi** · 08-24-2005, 09:18 PM

It's just easier to take mono PD's for everything. Every computer system I've used asks for mono PD's. If you worried about the cosmetic appeal of a FT, (boy, that's an oxymoron :D) make sure they are AR coated, and just tell them they will be dissimilar.

**drk** · 08-25-2005, 09:20 AM

What Jedi said!

**William Walker** · 08-26-2005, 09:34 AM

(I don't want this to sound arguementative)
It's amazing to me that there are professionals, those who would want to expand their scope of knowledge by investing their time into services like the optiboard, and be the same people who neglect simple details like mono pds. I see it said here by some that it's unnecessary for single vision lenses. How about the gentleman in a more recent post with a -18.00?, or patients with even moderare Rxs that have very dissimiliar mono PDs? I believe it's necessary. I also take mono heighths on single vision when an rx gets to be above about a +/- 4.00, or when their eye sits a decent amount away from the geometric center of the frame. Why? Because it is necessary to me. Why is that? Because I want to provide the best eyecare/eyewear possible. It means taking those extra few steps (that don't usually take more than 30 seconds) that others, in their ignorance, sidestep.
Sorry, I don't mean to rant, but it's a pet peev.

**mshimp** · 08-26-2005, 07:03 PM

Sounds like you are a good optician.You know what you are talking about.Why are you working for Costco?

**optoblog.com** · 08-26-2005, 10:15 PM

I've seen the light! I buy the argument that you should do the same thing for every patient. In the end that usually saves time vs. figuring out when you should or shouldn't do something. I especially agree about the higher powered lenses.

Originally Posted by mshimp

. . .do you ever experience errors using a pupilometer that you know is perfectly calibrated but indicates incorrect pds?

That's just it. I don't trust the optical lab freebie pupillometer to be perfectly calibrated. I won't use it.

**rbaker** · 08-26-2005, 10:21 PM

The gold standard for measuring interpupillary distance is not the pupillometer, its confrontation corneal reflection and a metric scale.

**Jedi** · 08-27-2005, 06:10 PM

Originally Posted by William Walker

I also take mono heighths on single vision when an rx gets to be above about a +/- 4.00, or when their eye sits a decent amount away from the geometric center of the frame.

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.

**Happylady** · 08-27-2005, 08:04 PM

I always take monocular pds with a pupillometer. If their eyes are very different I always double check with by shinning a penlight into their eyes and marking the corneal reflex with a marker on the demo lens.

If I am still not sure I measure each eye with a pd stick. I learned on a pd stick and am good with one. I think some young opticians don't even know how to use one to take a pd! I also will check what the pds were on their old glasses if I get an unusual pd.

I always double check myself on high rx's and progressives even if the eyes have similar pds.

**Pete Hanlin** · 08-27-2005, 08:47 PM

I know what a single vision lens is, but what on earth is a bifocal- do people still wear these antiquated lenses? :p Just kidding, sort of...

I'm not going to jump on the "how dare you take binocular pds" bandwagon, but in practice I would probably go ahead and supply monos for sv and bf wearers. The disappointing thing is the number of binocular pds being sent in with PAL orders (about 30% of orders each time I check orders coming into the average laboratory.

**Happylady** · 08-27-2005, 09:51 PM

Originally Posted by Pete Hanlin

I know what a single vision lens is, but what on earth is a bifocal- do people still wear these antiquated lenses? :p Just kidding, sort of...

I'm not going to jump on the "how dare you take binocular pds" bandwagon, but in practice I would probably go ahead and supply monos for sv and bf wearers. The disappointing thing is the number of binocular pds being sent in with PAL orders (about 30% of orders each time I check orders coming into the average laboratory.

Could it be that some of those 30% are people that have the same pds in both eyes so that they don't order with mono pds? For example if both eyes are 30.5 they might just order a pd of 61.

**Jedi** · 08-27-2005, 10:19 PM

Originally Posted by Happylady

Could it be that some of those 30% are people that have the same pds in both eyes so that they don't order with mono pds? For example if both eyes are 30.5 they might just order a pd of 61.

Or they forgot to take them period and thought, "he looked like a 32/32".;)