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.
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?
Last edited by AngeHamm; 10-18-2023 at 09:00 AM.
I'm Andrew Hamm and I approve this message.
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.
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?
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?
Last edited by NAICITPO; 10-17-2023 at 06:14 PM.
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.
https://www.optiboard.com/forums/sho...=polycarbonate
Uilleann it seems like people have been saying the same thing for quite awhile...
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.
No one has ever been sued in the US for using poly lenses.
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.
I'm Andrew Hamm and I approve this message.
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.
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.
Could we please cool it with the personal attacks? There's enough conflict in the world already. Thanks!
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No problem Steve.
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.
Last edited by Michael22; 10-18-2023 at 11:54 AM.
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
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