Patients allergic to polycarbonate?!

**OptiNovice86** · 12-01-2012, 07:28 PM

Hello my fellow Optii, I'm an LDOA in Ga and recently, I had a complain that she was not able see clear out here glasses. The Rx was modest, -.25 with some cyl on both eyes, single vision. I verified the RX, including pano tilt, vertex distance, and ocular height ;there was no error on my behalf. Her complaint was that there was a "blue haze" around the outer edges, but there was no polish on the lenses. One of my coworkers stated that; though few and far between, there are some patients who experience discomfort in a polycarbonate lense. This is the first time that I have ever heard such a complaint and theory to support it.

Feel free to elaborate......I'm just a little confused.

**Robert_S** · 12-01-2012, 08:00 PM

Chromatic aberration? That's exactly what it sounds like, which is not to say that it is. I think most people on this board would agree you probably shouldn't use polycarbonate anymore anyway.

It isn't an allergy, though.

**uncut** · 12-01-2012, 09:50 PM

I concur with your explanation, Robert_S. It is likely that the person is noticing the blue/violet end of the spectrum, especially at an angle through this RX. It is very common. Some people hate it, and others cope with it well. It is commonly felt that if the advantages of the device outweigh the disadvantages, satisfaction will be the result.

If this is the first time polycarbonate was used, and perhaps CR39 was used before, it will be a new phenomena. Pay attention to the Abbe number of the raw material used when dispensing, that will tell you the level of chromatic aberration that the material will create.

As an aside, when glass was commonly used, people used to notice the difference in visual qualities between their old glass lenses and new CR39s..............................

**OptiNovice86** · 12-02-2012, 06:24 AM

Actually, this was the first time this particular patient was fit with poly lenses. She has sworn CR39 for her previous three pair but, all of those frames were either full rimmed or Zyl. I felt the best the option was using the poly lense considering the frame was semi-rimless.

What about trivex? I typically only use trivex lenses when fitting compression drill mounts and conventional drill mounts...but would trivex be sufficient for a semi rimless frame? I'm going to assume the abbé value is going to be lower in a trivex lense correct?

Originally Posted by uncut

I concur with your explanation, Robert_S. It is likely that the person is noticing the blue/violet end of the spectrum, especially at an angle through this RX. It is very common. Some people hate it, and others cope with it well. It is commonly felt that if the advantages of the device outweigh the disadvantages, satisfaction will be the result.

If this is the first time polycarbonate was used, and perhaps CR39 was used before, it will be a new phenomena. Pay attention to the Abbe number of the raw material used when dispensing, that will tell you the level of chromatic aberration that the material will create.

As an aside, when glass was commonly used, people used to notice the difference in visual qualities between their old glass lenses and new CR39s..............................

**OptiNovice86** · 12-02-2012, 06:25 AM

Why shouldn't we be using poly?

Im still an apprentice, enlighten me....,

**Robert_S** · 12-02-2012, 06:35 AM

No, Trivex has the highest abbe of any material other than CR39 or glass. Basically, a poor optical material will refract the different components of light variably; that is to say, some colours will be allowed through faster than others. This is perceived as a blue or yellow hue particularly around the edges of objects in the periphery.

If you have the tools, surface a poly or 1.67 lens with around a 6 cyl and, looking through it, you will find this effect easily noticeable.

Reasons why Poly is poor:

low abbe value, hence high levels of chromatic aberration.
high chemical reactance; must not be exposed to solvents and will discolour over time as it reacts with particles in the air.
prone to starring at drill points unless treated carefully.

I personally don't use CR39 or 1.56 in supra frames either, because both will eventually chip. Also, the tension of the mount will create aberrations in materials with low tensile strength.

**Robert_S** · 12-02-2012, 06:38 AM

I don't say this to be critical, but you really shouldn't be dispensing unless you know the lens materials, lens designs and lens treatments (as well as how the Rx plays its part) absolutely thoroughly.

Although you will learn as you go along, it will be at the expense of your patients. Trust me, because I did the same thing.

**fjpod** · 12-02-2012, 07:39 AM

With all due respect to those that don't like the properties of poly...it is widely used and accepted. All materials have their downside. Trivex may be better in certain in certain mountings, in certain prescriptions, but it is not better in all cases. Poly has it's place.

leading others to believe otherwise, is...not being honest with yourself.

**Craig** · 12-02-2012, 08:34 AM

Originally Posted by fjpod

With all due respect to those that don't like the properties of poly...it is widely used and accepted. All materials have their downside. Trivex may be better in certain in certain mountings, in certain prescriptions, but it is not better in all cases. Poly has it's place.

leading others to believe otherwise, is...not being honest with yourself.

We use 90% trivex and 10% higher index, why would you use poly over trivex if both are available? We use some poly polarized ft's over a digital trivex polarized sometimes, but that is the only reason if money is not the issue.
Other than stock, we pay the same for trivex as poly anyway so why not use it as much as possible. We also edge all work ourself on a new ME-1200 set up for trivex so it processes like butter!

We do not take insurance so we do not have to deal with that upwell issue, we charge the same to all and they get 100% digital with ar.

**uncut** · 12-02-2012, 08:40 AM

Originally Posted by OptiNovice86

Why shouldn't we be using poly?

Im still an apprentice, enlighten me....,

Since I might have my non-dispensing-weekend-braincell-burning hat on..........I might be off on my answer.

Ahhhhhhh.....grasshopper!
The higher index lenses become surface reflectant, therefore warranting the extra expenditure towards a quality anti-reflection coating. Unfortunately, economics now will come into play.
Present your patient with options, and your logic to this point.........................
I would suggest that this patient may guide you, and might be willing to put up with the "blue horizon".

When assisting a patient in choosing a lens type, many factors come into play. Weight of lens, cosmetic thickness, surface reflectance, Abbe value, economics.

Each material will have it's advantages and disadvantages.....

**fjpod** · 12-02-2012, 09:06 AM

Originally Posted by Craig

We use 90% trivex and 10% higher index, why would you use poly over trivex if both are available? We use some poly polarized ft's over a digital trivex polarized sometimes, but that is the only reason if money is not the issue.
Other than stock, we pay the same for trivex as poly anyway so why not use it as much as possible. We also edge all work ourself on a new ME-1200 set up for trivex so it processes like butter!

We do not take insurance so we do not have to deal with that upwell issue, we charge the same to all and they get 100% digital with ar.

1. Trivex is thicker than poly.
2. Some people care about cost.

**rdcoach5** · 12-02-2012, 11:02 AM

Not all poly is equal and not all surfacing is equal The reseason cr-39 used to be hard for some glass wearers to adapt to was that the labs didn't know how to deal with it when it first came out.Also the quality of cr-39 was probably increased over time. With digital surfacing I now think cr-39 is optically better than glass that is not digitally surfaced. The same applies to poly so the question for OptiNovice is to ask his lab what brand of poly and how was it surfaced? Any digitally surfaced lens is far superior to the old grind, fine and polish method.

**Robert Martellaro** · 12-02-2012, 07:24 PM

Originally Posted by OptiNovice86

Hello my fellow Optii, I'm an LDOA in Ga and recently, I had a complain that she was not able see clear out here glasses. The Rx was modest, -.25 with some cyl on both eyes, single vision. I verified the RX, including pano tilt, vertex distance, and ocular height ;there was no error on my behalf. Her complaint was that there was a "blue haze" around the outer edges, but there was no polish on the lenses. One of my coworkers stated that; though few and far between, there are some patients who experience discomfort in a polycarbonate lense. This is the first time that I have ever heard such a complaint and theory to support it.

Feel free to elaborate......I'm just a little confused.

Rare. P/v (Prism/Abbe) = Lateral Chromatic Aberration. Low levels of prism (induced or prescribed) results in low levels LCA. Nonetheless, I've had one case where the client saw a faint red line along the horizon in daylight with Poly and low levels of LCA. Trivex reduced, but did not eliminate it. I've read of other cases- best guess is it's due to interaction with the eye's chromatic aberration.

**OptiNovice86** · 12-02-2012, 08:39 PM

I appreciate that Robert. I would like to consider myself pretty knowledgeable of lense materials and do quite well with dispensing. I have just never heard of something like this before

**OptiNovice86** · 12-02-2012, 08:40 PM

Thank you!

**OptiNovice86** · 12-02-2012, 08:43 PM

I really appreciate the answer! As you know, I am just an apprentice but in no way means that I don't know some of things. I usually fit patients into hi index lenses, normally 1.67. I like 1.74, I wear it myself but as you stated, economics do play a pivotal part in what a patient will choose.

**OptiNovice86** · 12-02-2012, 08:44 PM

Thank you, I will definitely contact my lab and ask that question. I do know that 'lifestyle' poly is crap!

**OptiNovice86** · 12-02-2012, 08:45 PM

Thanks Robert for the insight. I sincerely appreciate the honest answer. As you know, some of our fellow opticians aren't necessarily the most patient and understanding of people when dealing with a young grasshopper such as myself.

**Browman** · 12-02-2012, 10:55 PM

Originally Posted by OptiNovice86

Thanks Robert for the insight. I sincerely appreciate the honest answer. As you know, some of our fellow opticians aren't necessarily the most patient and understanding of people when dealing with a young grasshopper such as myself.

As long as we're discussing other lens materials:

We're supposed to push poly by "informing" the patient that, in the event of a car crash, CR-39 will explode on impact with the airbag, go into the patient's eyes, and permanently blind them. I know that anecdote does not equal data, but I've at least seen CR-39 get run over by a vehicle going at a high speed, and while the lens didn't hold up, it also didn't turn into dozens of death shards. I'm also skeptical that if the material is that dangerous that there wouldn't be more "scare advertising" against OTC plano suns that have CR-39 lenses vs. OTC PCs. As I result I shy away from this particular tactic and simply lay out the various other benefits of PC vs. CR (UV, etc). Any input from anyone?

**Wes** · 12-02-2012, 11:30 PM

Browman, don't go there. It's cheap and sleazy used car salesman tactics that you never want to have associated with your reputation. Tell them as much true information as they want. Many patients enjoy a continuing education and actually enjoy showing off how much more they understand to their friends. Treat them like your favorite grandma and you'll have appropriate, ethical sales and loyal customers that will follow you.

Ps.
You should probably take that down before someone quotes you.

**rdcoach5** · 12-03-2012, 08:39 AM

Originally Posted by Wes

Browman, don't go there. It's cheap an sleazy used car salesman tactics that you never want to have associated with your reputation. Tell them as much true information as they want. Many patients enjoy a continuing education and actually enjoy showing off how much more they understand to their friends. Treat them like your favorite grandma and you'll have appropriate, ethical sales and loyal customers that will follow you.

Ps.
You should probably take that down before someone quotes you.

Wes, what exactly was wrong with Browman's post ? We get bombarded all the time at continuing ed courses about "Duty to Warn" meaning if we don't at least offer poly to our customers and they get an injury to their eyes, they can sue.

**Wes** · 12-03-2012, 09:19 AM

I think that far exceeds "duty to warn" and goes into "make incredible exaggerations to scare your patients into spending more money".

**Robert Martellaro** · 12-03-2012, 09:49 AM

Originally Posted by OptiNovice86

Thank you!

You're Welcome.

Originally Posted by OptiNovice86

I appreciate that Robert. I would like to consider myself pretty knowledgeable of lense materials and do quite well with dispensing. I have just never heard of something like this before

I saw this question in J. Sheedy's old newsletter about 10 years ago (there was usually at least one ophthalmic optics question per newsletter), but this question never received an answer. To the best of my knowledge, it remains somewhat of a mystery. You might try your question over at the Ophthalmic Optics forum; Darryll Meister reads that routinely and might have some further insight.

**Browman** · 12-03-2012, 10:16 AM

Originally Posted by Robert Martellaro

Browman, don't go there. It's cheap and sleazy used car salesman tactics that you never want to have associated with your reputation.

I know it's sounds sleazy, which is why I have a problem with it; what I'm asking is, should my patients be concerned about CR-39 vs. car crashes/airbags, or is this something that the higher-ups have developed for just such used-car-sales purposes? If there's a real, actual danger, I'd like to know.