I can't get a straight answer.
Are Trivex and Mid index the same? Or is Trivex one type of Mid-Index?
Harry
I can't get a straight answer.
Are Trivex and Mid index the same? Or is Trivex one type of Mid-Index?
Harry
Trivex and Mid-Index are not the same, because 1.56 is considered a mid-index lens. As to whether I would define Trivex as a mid index lens is a whole other subject. If you consider Polycarbonate to be in a separate index class then the plastic class (1.50, 1.56...1.74) then I don't understand how you can consider Trivex to be in the plastic series.
Here's my take on it. cr-39 1.49 glass 1.523 and trivex 1.53 are all what I would consider standard indexes. Ormex 1.56 and poly 1.59 are mid indexes. 1.60 and over are hi index. Just a lab guys perspective.
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
Why would you consider 1.59 a mid index and 1.60 Hi index?
Have to make the cutoff somewhere. I could list numerous superfluous reasons from "I just don't like poly" to "because no literature I've ever seen calls it hi index, while the lit does call 1.60 hi index". Bottom line is, to differentiate polycarbonate from the other hi index acrylic/polyeurethane plastics, I choose not to consider it hi index. Also, I don't like to get patients confused thinking it's a hi index material because frankly, it stinks for high rx. Ever look at a high add poly progressive with prism thinning through a manual vertometer? You can see the chromatic aberration. Also with prism jobs. 1.67 is almost as bad. Basically, the patient base thinks of it as not as quality as hi index because it has had a distinction in the market for so long. I think its not as quality as hi index because its not. unless you want to shoot it with birdshot to prove the pellets wont go through. But you can do that to trivex too.
What we hear is plastic, poly, hi index. Yeah, plastic isnt plastic, its a resin. Yeah poly is so near to hi index that it may as well be. Yeah, hi index is plastic. Confused yet?
In a perfect world, or my own shop, whichever comes first, the only lens materials sold would be cr-39, glass, trivex, 1.60 and 1.70.
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
Anything between a base index (CR-39 or crown glass) and 1.60 should be considered a mid-index lens (1.60 - 1.67 are hi index, >1.70 ultra hi-index). Otherwise it just get's too complicated. Four categories - base, mid, high, ultra-high.
+1
I guess I consider Trivex mid index. To me mid index is from 1.53 to 1.57. High index is 1.59 and up.
Harry what is the point? Why do you need to know if is a mid index or not?
Is it for insurance reasons? Let us know.
by index, yes it is. it has some advantages over other mid index lenses though. Weight, impact resistance, etc.
a civic is a car, but not all cars are civics.
I've had optical lab individuals use the terms "midindex" and "trivex" interchangeably.
Like when I order "high index" from a lab, do I get 1.6, 1.66, or 1.70?
Harry
Originally Posted by mshimp
Cr-39 and crown glass have always been my "standard" index. Anything above that was Mid-Index until you got to poly, which I've always sort of referred to as a seperate beast(although we all know it is a higher index material). Anything above Poly(1.59) has my regognition as a "High Index" lens. So, what is Trivex? It's mid-index. And a Darn good Mid-Index it is!! I love the smell of Trivex in the morning! :)
Chris Beard
The State of Jefferson !
I'm a Medford man – Medford, Oregon. Up in Medford, we take our time making up our minds."
Because it doesn't smell like 1.67 or 1.74?
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
Its like buying a soft drink at a fast food establishment. Their large is however many ounces they say it is. Their medium is the number of ounces they say it is and their small is the size they determine.
These sizes may or may not have any relation to sizes at another fast food chain.
So in my opinion they can be what ever you decide you want to call them. If you use different labs they may call certain items mid index while another calls them high index.
Thayt was my point, I call them what I think they are, and differentiate them the way I want my patients to. I do see the logic in calling Trivex mid index, as I consider it a good sub for polycraponate.
Super hi index? Yes, thats a good point too.
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
Maybe they should refer to the 1.90 as Mondo Index?:D
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
In the Vision Council monthly shipment reports that lens manufacturers supply the information, the breakdown descriptions were once listed...
less than 1.525 RI standard index
1.525 to 1.575 RI mid index
1.575 to 1.625 RI high index
greater than 1.625 ultra high index
poly is treated as its own animal and has its own section.
For the last year or so, the headings list only the RI ranges plus poly, but the values are not tagged as standard, mid, high etc...
Jim
Jim Schafer
Retired From PPG Industries/
Transitions Optical, Inc.
When you win, say nothing. When you lose, say even less.
Paul Brown
I like super-DUPER-hi index better.
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
Jim,
I am curious as to why polycarbonate would have its own section? What is the reasoning behind that?
Thanks!
Duh, Fezz.
It's because they're Featherwates.
Stupid question.
yes, a type of mid-index.
Last edited by KStraker; 02-16-2010 at 08:14 AM.
Hi Fezz,Jim,
I am curious as to why polycarbonate would have its own section? What is the reasoning behind that?
Thanks!
My guess is that back in the day, the Polycarbonate Council lobbied for it to track shipments. That is only a guess though.
The categories designated with refractive index ranges also are tagged Hard Resin....poly of course is not hard resin so that is another difference.
have a great day,
Jim
Jim Schafer
Retired From PPG Industries/
Transitions Optical, Inc.
When you win, say nothing. When you lose, say even less.
Paul Brown
CR-39 -> 1.498
Mid-Index Plastic -> 1.53 to 1.56
Trivex -> 1.53
Poly -> 1.58
1.60
1.66
1.67
1.70
1.71
1.74
(anything with a number for a name is high-index, although I've seen anything 1.70 and above referred to as "utra high-index" or "hyper-index")
Trivex and Poly get "special" catagories because they are processed differently in the lab than "plastic" even though Trivex IS in the Mid-Index range (and technically they are all "plastic" as opposed to glass).
You shouldn't just order a "high-index" lens from your lab, you should specify which one you want (1.60, 1.67, etc). If they aren't calling and asking which one you want, I'd say that's a problem.
Mid-Index and Trivex should NOT be used interchangably because they have different material properties.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
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