CR-39 vs. Polycarbonate

[drk]

lol, So touchy doc. How ominous. Remember: I've read your previous posts, on optiboard. **cue menacing music**

Don't try to disqualify me by telling me to stick to "spinning dials". I take that as a big time insult. You know a small sliver of what I know about vision care. Don't act like an @$$ and show some respect.

[drk]

Anyone ever played with an uncoated poly lens? Scratches instantly with nearly anything touching the lens.

What is an uncoated poly lens? Is that something in a lab?

[NAICITPO]

https://www.2020mag.com/article/does...atients-vision

This idea that polycarbonate is crap... most people will never have an issue in polycarbonate nor will they be able to tell the difference between trivex and polycarbonate. When you get above 4 diopters we can start having a conversation about abbe.

[AngeHamm]

I have been told by multiple lens reps that AR adheres better to the substrate of poly than CR39 or Hi Index, and that AR coatings will be marginally more​ scratch resistant on poly, not less. Am I mistaken?

[Elvis Is Alive]

What is an uncoated poly lens? Is that something in a lab?

Back many years ago before the age of digital surfacing, you would have to back surface semi-finished (front side) progressives. Poly had to go thru a backside hardcoat process. i believe we used UV curing for that in a special poly hard coat machine. If you took a lens out before the backside hard coat was applied, you could really get a sense of how soft poly really is.

I think that is correct. Lab experts can chime in.

[jefe]

Poly is not an upgrade from cr39.

CR39 is chemically inert. Poly will be junked if exposed to chemicals(alcohol, acetone, etc.), it doesn't tint well, optics are worse, CR39 will have much better long term AR performance over poly. Poly always has problems with AR coatings. Anytime someone brings me an old lens with peeling coatings, it is always poly. CR39 is a great material. Trivex is wonderful. Those 2 will cover 75% of your jobs if not more. 1.60 for the rest. and occasionally 1.67. Poly should be stricken from the optical record.

I wholeheartedly agree with the above.

[jefe]

I have been told by multiple lens reps that poly adheres better to the substrate of poly than CR39 or Hi Index, and that AR coatings will be marginally more​ scratch resistant on poly, not less. Am I mistaken?

My guess is you meant to say "...AR adheres better to poly than CR-39 or high index..." And if that's what you meant to say, I disagree with that.

[jefe]

https://www.2020mag.com/article/does...atients-vision

This idea that polycarbonate is crap... most people will never have an issue in polycarbonate nor will they be able to tell the difference between trivex and polycarbonate. When you get above 4 diopters we can start having a conversation about abbe.

If there's a material non-adapt, it's usually poly.

[jefe]

CR-39, Trivex, MR-8, MR-10:

poly: not so good

[Barry Santini]

C'mon people.

Polycarbonate's optics are great except for extreme powers.

There's very little usefulness for 1.6. It's a me-too product.

I hate to say it, but if you don't like polycarbonate youdon't know what you're talking about. You're just a hater and you're not experienced or scientific.

Whew! Pretty harsh words there drk!

It is interesting to note that Germany, Austria and the UK do not agree with you at all.

there is clear room for discussion on this point.

[NAICITPO]

CR-39, Trivex, MR-8, MR-10:

poly: not so good

MR-10 same abbe as poly. Do you notice a lot of 1.67 aversion? How can one be AWFUL and the other with the same Abbe be good?

Whew! Pretty harsh words there drk!

It is interesting to note that Germany, Austria and the UK do not agree with you at all.

there is clear room for discussion on this point.

I'm here for a discussion.

It seems there's a dogmatic dislike of poly with not much to back it up.

"The optics with poly are bad"

Really? How many issues of aversion do you see? I've worked in predominately polycarbonate practices and I just don't see them very often. Part of that is under 2 diopters of power according to Dick Whitney you will not have issues:

"Certainly for powers below 2 Diopters, lateral color will not be noticeable to the wearer. For those powers at 4 Diopters and above, if lateral color is a concern and yet impact considerations are important, materials like Trivex, with an Abbe of 45, is also an option."

If low Abbe value causes lateral color errors why do you not see them often with MR-10? I think it is fair to say that we use 1.67 with higher Rxs and yet we don't see aversion.

Are there other reasons besides abbe that you would say poly has poor optics?

[Uilleann]

Poly hating was sooooo 1994! LOL

The proof is in the pudding. I challenge ANYONE under say a +/-3.00 to try to visually discern lens material by optics alone in a truly blind test. Millions upon millions of people all over the planet successfully wear poly lenses with no issues whatsoever. The amount of "better" over those powers is completely subjective as well.

Objectively, Abbe values do not agree with visible CA in low and moderate ophthalmic lenses, properly fit. Science just isn't on your side there. It's been proven again and again, both on and off the boards here. If you prefer to fit other materials because...reasons - cool! Do that. But continuing to utterly trash a material for non existent visual aberrations below human perceptual limits comes of as not only smug, but unprofessional, and frankly silly in the extreme.

[NAICITPO]

https://www.optiboard.com/forums/sho...=polycarbonate

Uilleann it seems like people have been saying the same thing for quite awhile...

[AndyOptom]

Having dispensed thousands of poly lenses, from stock to premium free form designs, I have not noticed significantly more complaints than I get with any other lens material.

I believe it's because I am up front with patients, with respect to the trade off between scratch resistance and impact resistance, etc.

And for those saying poly chips and cracks, etc, I daresay any material is fallible in that respect. For patients whose concern is shatter/impact resistance, I often request the poly lenses be ground slightly thicker, to the relief of one patient who had a splinter ricochet during woodworking and embed itself in the poly lens instead of his eye.

As for chromatic aberration, I wouldn't fit poly for patients who are extremely particular about their vision, or whose lens fittings dictate otherwise (long vertex distance, etc).

Granted, I live and work in Asia, which is much less regulated and/or litigious than the West, so your mileage may vary.

[Uilleann]

No one has ever been sued in the US for using poly lenses.

[AngeHamm]

My guess is you meant to say "...AR adheres better to poly than CR-39 or high index..." And if that's what you meant to say, I disagree with that.

I did mean to say that, thanks. I had a VP from Carl Zeiss tell me that and I've been repeating it as gospel because this woman really knew her stuff back in the day. With all due respect, I'm less interested in anecdotal disagreement than I am in seeing studies showing some evidence.

[AngeHamm]

If there's a material non-adapt, it's usually poly.

True. But i've seen it happen exactly three times in the last fifteen years, so that's not going to impact my material choice much.

[Uncle Fester]

A New Years day discussion from OptiBoarders who, like me, find themselves sometimes posting on holiday's!

This one is from 2006:

"Don't blame all poly-- look at the hard coating"

"What chemical issue you are having with Poly? What is happening to a poly lens? You may actually be complaining about the grade of hard coating used and the processing after surfacing. I know there are a number of excellent AR coated poly finished lenses that will stand up great.

Depending on the lab and the treatments used for semi-finished is where you may have experienced the problem.

As for Abbe value. This is my number one heard complaint from opticians and the hardest one to prove. My opinion is many problems get blamed on Abbe value that have nothing to due with chromatic vision issues. As a matter of fact I have yet to see any optical retail establishment with equipment capable of testing a lens for an abbe value problem.

How do you determine a customer has a lens with an abbe value problem?

I think you see more problems related to hard coating that have incorrectly been identified as a lens abbe value as the problem. Opticians are trained about abbe value to my knowledge there is little factual training for opticians on hard coating and AR, much less what poor or degrading hard coat can do to the optics and performance of a lens.

I am not saying that there are no real abbe value issue it is just they are a very small part of the problems encountered with lenses not performing as desired."

AWTECH's post number 34 is worth a read as well.

https://www.optiboard.com/forums/sho...ght=Poly+dirty

When I first joined OB I remember a post from someone saying the industry was very close to discontinuing its use in the 80's (?) because of its problems in manufacturing. A dominant lab in California was fed up with problems and ready to not use it in there labs. The manufacturers literally cleaned up their act after that threat. Not the least of which was because of how profitable a railroad tanker of the cold liquid was. At least that's my memory.

[Elvis Is Alive]

Personally, I notice chromatic aberations with Poly, 1.67 and higher indexes and have since i was a kid.

Example: Looking at the edge of a white paper while looking off-center I see the color shift. Do I find it annoying? A little, enough that I choose not to wear those materials.

For reference, I am a -3.25 sph at distance OU.

It is obvious as well checking power on a lensometer. Glass, CR39, Trivex all have very sharp target lines where poly is clearly more fuzzy.

[Kwill212]

Don't try to disqualify me by telling me to stick to "spinning dials". I take that as a big time insult.

That was the point.


You know a small sliver of what I know about vision care. Don't act like an @$$ and show some respect.[/QUOTE]

You lost all of my respect about 6 months ago and it isn't going to change.

[Steve Machol]

Could we please cool it with the personal attacks? There's enough conflict in the world already. Thanks!

[Kwill212]

No problem Steve.

[Michael22]

I will also say I have only ever seen one poly non-adapt, and a whole heck of a lot of people put in poly that have never come back and complained. Most of them show up asking for it actually.

[chamilun]

had a pt last week with 4 pairs of glasses. the only ones he could wear were from 2017. so he had 2017, 2019, 2021 and 2022.

guess what the difference was?

trivex. the 2017 glasses were trivex.

have had a handful of patients over the years who had issues with polycarbonate. but its a small %. I dont rx NVO in poly for this reason.

but as mentioned, there are different grades of polycarbonate lenses. different center thickness. all that.

and as a sidenote, my eyes hate polycarbonate material. -5.50/-5.00. 1.67 is just fine tho for whatever reason

[dima]

I don't even mention safety because to me it's a red herring. The last thing I've seen in my 35 years is an eye injury from a lens of any kind.

I don't know about you, but I don't get coating failures on polycarbonate lenses, ever. At least, not enough to make a difference.

Plus, how long are you expecting these lenses to last, anyway? Five years? If you're looking to make some classic Rx sunglasses that last for a decade, OK, we can talk, but most people (and especially with VCPs and the quality of frames, anymore, and with the downmarkety-turn-and-turn-and-turn el cheapo glasses so you have a blue pair and a purple pair) a pair of glasses is going to last 3 yrs, max.

I think the trick is not to build the ultimate glasses that last forever, but to make a nice 2-3 year pair and get a new pair. That seems to be the trend.

Keep the cost to get into glasses low. This applies to:
1. new wearers' first pairs, because they're not bought into the whole "I really DO need glasses" mentality, yet.
2. kids because they grow so quickly and progress
3. old folks = cataracts and penury
4. any presbyope that wants computer glasses and SVNO designs. They like multiples.

The people that truly appreciate quality glasses are
1. Ametropes since a young age. They know glasses, by now. They know the impact on their lives.
2. High ametropes.
3. Advanced presbyopes. Multifocal designs are critical.
4. I would say Rx sunglass wearers, because they're a "positive" purchase instead of a "negative" purchase. ("You only sell two things: good feelings (sunglasses) and solutions to problems (dress Rx)". Good feelings trump problem-solving every time.)

Ok, we all know that we Need also cheap product, we can sell polycarbonate but only I do not consider It a top plus material anymore