Polycarbonate vs. Trivex (NEW THREAD - edited by Moderator)

[Billy Brock]

Pete has always stood by his motto: choose the best product for the job for each individual situation...... I appreciate all the help he has given me personally to help process my poly Rx's ...... thanks and the poly orders do seem to be doing somewhat better by utilizing the technical info you have so kindly posted ............. thanks also to Chris Ryser for sending me the chemical poly polish. I'm with Pete on trying to choose the absolute best material based on optics, mounting selection & Rx.


There is a special factor in my personal opinion only that DOES justify any additional fee for Trivex material: in over 26 months of active use I have never replaced one single lens due to material failure of any sort ....................... it sure makes me happy to stand in line at the bank to deposit $ $ $ instead of sitting in the banker's office begging for a loan to cover lost expenses due to lens material failures.

"IF" the patient receives better visiual accuity ,in my opinion that's just a bonus...................................... as far as "easier" drilling goes, depends on how you define "easier" ? ? ? ................................. my personal definition includes: I don't have to be careful, I don't have to chamfer edges, I don't have to use nylon washers to cushion , I don't have to worry about any chemical compatibility, I don't have to use chemicals to retard splitting, crazing & cracking, I don't have to worry during the mounting and pre-alignment phase....................... that being said , Trives IS easier (in my situation) to work with because I'm confident it will not be returned for a material failure redo.................. bottom line, my choice for Trivex in drill mounts rests with the "ease" of processing and no failures ........ as always this is only my personal observation & opinions based on my extended use of PPG products.

hope everyone had a nice holiday season ...... looking forward to 2004 with all you Optiboarders


B

[Laurie]

Hello Everyone,

Maybe I skimmed through this thread too quickly, but I did not notice anyone talking about the ABBE VALUE of TRIVEX...MUCH better than polycarb!

Of the five specular aberrations, clients will subjectively complain the most about chromatic aberration. Of the aberrations, we can adjust for 4 of them through lens design...the 5th (chromatic aberration), cannot be adjusted for...it is inherent in the material. The best we can do is choose lens materials with the lowest amount of chromatism, which is indicated by a high abbe value.

A high abbe value indicates low amounts of chromatic aberration (chromatism).

Trivex is better both optically and practically (processing).

Pete, you know I love you like a brother...but are you still singing the praises of polycarb over high index, and now, trivex?

Must I report you to Clifford Brooks and Moe Jalie?

smooch,

; )

Laurie

[For-Life]

I want to address the abbe debate. I saw previously that someone wrote that they wore ploy and they got tunnel vision.

Over the last few years I have worn 1.67, 1.6, CR - 39, Trivex (Phoenix), and Poly (Essilors Airwear aspheric and non-aspheric). I am currently -5.50 OU.

I have not had difference in my vision in either of these products. Now not having any astigmatism, the aspheric or non-aspheric lens will not really have an effect. But I have had no colour deviations, nor any vision problems. We have used the Airwear Aspheric lens on a lot of our customers ranging up to 11 diopters, and the 1.67 (which has the same abbe value) up to about 13 diopters. We have not had any vision problems, and if anything have had more success. Actually recently I had someone in who had glass lenses and he had an RX of (it is not the exact value, but of by maybe only a quarter diopter or 10 degrees)

-7.00 -7.00 x 090
-6.00 -7.25 x 090

He developed a cist on his nose from the weight of the glass, so we put him into the Airwear Aspheric. He said it was the best vision that he has ever had in his life (he did not have a prescription change from his last pair). So I honestly believe that the Essilor Airwear Aspheric (we always do it with Crizal) is one of the best materials on the market, even though it has an abbe value of 32.

The only problem is the cracking in 4-points. But I am going to try edgit and poly edge polish.

[For-Life]

I saw that the survey bumped this post so I will give you an update. I have been using Edgit on my poly rimlesses and I have not had one crack since.

[Tjcjdc9462]

Trivex tints very well. You can do gradients and sun tints just like CR39.

[dadoody]

The optician told me they think polycarbonate is better for my 3 piece mount rimless glasses. They say it is softer and gives better than Trivex, so they say it won't crack.

[Tjcjdc9462]

That is absolutely incorrect. The only reason they are telling you that is because they don't sell trivex and they don't won't to lose a sell. Take it from someone with 15 years experience who sells approximately 10 pairs of Silhouettes a week alone, you will regret your purchase if you get poly. My advice is to keep shopping.

[For-Life]

We do a lot of poly in a rimless. You just have to use a good product to seal in the cracks. If you use that then you will have no problems.

[blackbirdy4444]

I said I would post the info on Friday, and I am still trying to get more specific data on the impact resistance of Trivex. Unfortunately, I don't have some of the really cool instruments that R&D gets to use here in my office, or...

;)

I think the poll is rather interesting, however. Even after all the discussion, people are voting for option number one. Only three have voted for the correct answer (#2), and one of them was me, so...

Concerning Chip's question on eyes lost to various lens materials, I have always thought that anyone over the age of 18 should be able to choose whatever s/he wants for their lens material and design (including 1.8 index at 1.5mm if they so desire- given a thorough education concerning the material's tendancy to break). Of course, I am a proud card carrying member of the Republican Party's Conservative Branch (R.C.P.B.). Sorry Steve, that was too good of a description to pass up! Plus, its fitting- since I received my new voter's registration card just last week... just in time to vote for the President's younger brother!

Really though, what have we come to in this country? Perhaps we should keep people from buying Corvettes (they are capable of acheiving very unsafe speeds). Maybe we should require auto dealers to adhere to a "Duty to Warn" if their client doesn't purchase a Volvo (which is, after all, the safest car out there).

Perhaps John can look up some figures on just how many lenses are returned for shattering in the UK (since they allow the use of materials and designs the FDA has outlawed here in the states)?

Is ninety nine percent of the whole poly/trivex/whatever push just to protect ourselves from lawyers, or to protect the public?
I sure hope not! Polycarbonate stands as a terrific material even without the fact that it is the most impact resistant material currently used for ophthalmic lenses. Its light weight, high index, UV blocking properties, and ease of manufacture makes it a very attractive product.

Polycarbonate is the only ophthalmic product out there (other than Poly Methyl Methacrylate, which Chip is familiar with from his PMMA contact lens days) that is a thermoplastic resin. This means a manufacturer can take it in solid form, heat it up, press it into a shape, let it cool and BAM- you have a lens (whole process takes about five minutes, and you can chop up the material left over at the end of the process and sell it to other manufacturers who use lower grade polycarbonate for re-use).

All other materials are thermoset:
Allyl Diglycol Carbonate becomes CR-39... it must be activated (which makes the material start to heat up) and "sets" or "cures" into its cast shape. Once it has been locked into its final form, it will never melt again (it will ignite if sufficiently heated, but it will never be molded again), and anything left over at the end of the process is simply wasted. Also, it takes a considerable amount of time to properly cure the material if you want to end up with a quality product.

Methacrylate becomes your mid-index materials and is generally a UV curable product (you cast it and plop it under a UV lamp and it hardens). Once its set, that's it for this material too. The advantage of this material is that UV curing doesn't usually take as long as some other forms of curing.

Styrene and Thiourethane become your higher index materials and producing them involves toxic by-products that are basically unacceptable given the the EPA (Environmental Protection Agency) in this country. That is why most of your higher index materials come from abroad (mostly Japan). This is a cured product as well, and the curing can be very tricky.

Again, sorry for the length... however, the point is (I'm trying to find a way to win Steve over to Polycarbonate, and he is a proud card-carrying member of the Green Party), if you like efficiency and a relatively "green" product, Polycarbonate is for you! Given proper processing, poly is a financial, optical, manufacturing, environmental, and retail dream!!! Cue the poly theme song "Poly's great, poly's good, its used in lenses and in hoods" to the tune of the Barney song...
Thus concludes this installment of "Poly- A better way of life!"
;)

Clearly your handle on the various manufacturing technologies of monomers etc is great. However, you fail to mention the fact that the fabulous way in which poly is made directly results in a great deal of internal stress that creates yet another reason that human beings do not see well out of it. Low ABBE, heightened amounts of internal stress, poor coating capabilities....

No offense here, but Essilor's main reason to promote poly as heavily as they do is because it costs them the least. They charge more for it than other superior materials and purposely mis-market it. The FDA gives Trivex and Poly the SAME impact rating of >60x that of CR39. That is the highest it goes. Essilor owns and manufactures more poly than anyone, therefore they promote it. Not because it is good for the masses.

Drilling a poly is a huge mistake. It is not a matter of ''IF" it will crack, it is a matter of "When".

I am currently working for HOYA and have helped numerous private practitioners transition away from this horrible material. The Triangle (so to speak) of perfect lens balance good ophthalmic optics, light/thin, and impact resistance. This makes Trivex and its derivatives the best possible lens material to put MOST people in. In higher power ranges, patients deserve to be put into a 1.67. Poly has in many respects become the 'poor man's' high index because we can buy it cheap and surface it to a 1.0. Would you like to comment on how good an idea that is? Why don't you mount ANY 1.0 poly in a full metal frame and then watch it flex with the last turn of a screw driver. And then we wonder why people don't see well.

In the past, there were times that availability made it tough to take a person out of poly, but those times are gone.

Your explanation of poly and its manufacturing characteristics is really cool, and clearly well informed. I don't really feel it is fair though when your remark that poly is "a better way of life". People don't see well out of it!!!! They now have an alternative that is just as safe. I don't understand why you would market an outdated technology at full price! Would you pay full price for a ten year old car?

[Judy Canty]

Ummm...5 year old thread and counting.

[chip anderson]

Why do we even rate or care what the tensile strenght of lenses are? No one is going to pull them apart. Has nothing to do with impact resistance. Has nothing to do with scratch resistance. Has very little if anything to do with distortion in manufacture or mounting.

Chip

[HarryChiling]

I know this is an old thread, but I have to ask. When poly is compared to trivex in impact resistance, is the base curve an power taken into consideration?

Reason I ask is, the flatter a curve gets the less impat resistant the lens becomes no matter what the material. Since poly has a higher index that trivex the poly lens would aslo have a flatter base for the same power as a similar trivex lens would. Has this been factored in or are we looking at a standard base across all materials?

BTW, I choose wrong.:hammer:

[DragonLensmanWV]

I know this is an old thread, but I have to ask. When poly is compared to trivex in impact resistance, is the base curve an power taken into consideration?

Reason I ask is, the flatter a curve gets the less impat resistant the lens becomes no matter what the material. Since poly has a higher index that trivex the poly lens would aslo have a flatter base for the same power as a similar trivex lens would. Has this been factored in or are we looking at a standard base across all materials?

BTW, I choose wrong.:hammer:

In choosing wrong, you chose wisely.:D

[hcjilson]

I haven't checked with Pete lately...but now that Essilor has released Definity in Trivex, perhaps he has upgraded his opinion of the product.