Trivex thickness

[oxmoon]

A lady is coming in this afternoon who has low visual acuity in one eye and currently wearing poly. I think trivex would be a good idea, but don't know if thickness would be an issue. Does trivex generally make up to a similar thickness as poly? I know there is a lens thickness calculator somewhere on this site, but can't seem to find it.

[optilady1]

I don't think trivex thickness becomes an issue until about -10 ish. What's the rx, that's the only way anyone here is going to be able to help.

[Uncle Fester]

A lady is coming in this afternoon who has low visual acuity in one eye and currently wearing poly. I think trivex would be a good idea, but don't know if thickness would be an issue. Does trivex generally make up to a similar thickness as poly? I know there is a lens thickness calculator somewhere on this site, but can't seem to find it.

Bookmark this site and explore it for phenomenal info!

http://www.opticampus.com/tools/thickness.php

I'm curious- why is a lab tech deciding material?
(Yours is not to question why-
Yours is but to grind and grind!)

The general rx would also be helpful.

[oxmoon]

I started in the lab but am not really a lab sort of person so they moved me to the "sales floor", where I do much better. Script for this lady is -3.25 with add of 1.50 in right eye, to be duplicated in left eye. No cylinder. Thanks for the link Uncle Fester. I have saved it.

[Uncle Fester]

What's your thinking to change to trivex?
If they're happy in poly why fix what isn't broken?
Now give me a minute to run for cover as the abbe patrol takes aim! :)

[fjpod]

What's your thinking to change to trivex?
If they're happy in poly why fix what isn't broken?
Now give me a minute to run for cover as the abbe patrol takes aim! :)

Heck, I agree with ya.

Trives is going to be a little thicker in -3.50. As someone else said use Opticampus.com and check it out.

[Robert Martellaro]

A lady is coming in this afternoon who has low visual acuity in one eye and currently wearing poly. I think trivex would be a good idea, but don't know if thickness would be an issue. Does trivex generally make up to a similar thickness as poly? I know there is a lens thickness calculator somewhere on this site, but can't seem to find it.

You can get a pretty good estimate by comparing the refractive index.

(1.53 - 1.00) / (1.586 - 1.00) = 0.904, or about 10% thinner than Trivex.

[RT]

(1.53 - 1.00) / (1.586 - 1.00) = 0.904, or about 10% thinner than Trivex.

That math only works if your lab surfaces both materials to the same CT. But many labs standard setup is to surface poly to 1.5mm CT, and Trivex to 1.3mm CT. They only surface poly to 1.0mm if you pay extra. So the poly lens might be starting 0.2mm thicker than Trivex to begin with. With those assumptions, I laid out a test job with one eye Poly and one eye Trivex. The poly lens is 0.1mm thinner at the thickest point, but 0.1 mm thicker at the thinnest point. And the poly lens weighs more. I choose a pretty square frame...I probably could have engineered the frame to make the Trivex lens thinner everywhere.

You get the point. In this case, you'd be hard pressed to say that they poly lens was thinner. It is definitely not 10% thinner. But it would be heavier (7 grams to 6 grams = 16% heavier). Although it might be easier if you could say "Higher index of refraction = thinner lens", that's not always the case. Some ultra high index products require 1.5mm CT, depending upon the lab and whether or not they have a cushion coat. That would make the end product thicker than a slightly lower index that can be surfaced to 1.0mm CT. Higher index does not always equal thinner lenses.

[Oedema]

That math only works if your lab surfaces both materials to the same CT. But many labs standard setup is to surface poly to 1.5mm CT, and Trivex to 1.3mm CT. They only surface poly to 1.0mm if you pay extra. So the poly lens might be starting 0.2mm thicker than Trivex to begin with. With those assumptions, I laid out a test job with one eye Poly and one eye Trivex. The poly lens is 0.1mm thinner at the thickest point, but 0.1 mm thicker at the thinnest point. And the poly lens weighs more. I choose a pretty square frame...I probably could have engineered the frame to make the Trivex lens thinner everywhere.

You get the point. In this case, you'd be hard pressed to say that they poly lens was thinner. It is definitely not 10% thinner. But it would be heavier (7 grams to 6 grams = 16% heavier). Although it might be easier if you could say "Higher index of refraction = thinner lens", that's not always the case. Some ultra high index products require 1.5mm CT, depending upon the lab and whether or not they have a cushion coat. That would make the end product thicker than a slightly lower index that can be surfaced to 1.0mm CT. Higher index does not always equal thinner lenses.

What that guy said You can only rely on higher index = thinner if you're talking equal CT, and often more important, a lower index might be alot lighter in weight. I thought trivex was available in CT=1mm? No?

[Speed]

So the poly lens might be starting 0.2mm thicker than Trivex to begin with.

Could you hold up your thumb and forefinger that close together and show us actually how much thicker that is? Also might say that trivex is always lighter.

[Uncle Fester]

That math only works if your lab surfaces both materials to the same CT. But many labs standard setup is to surface poly to 1.5mm CT, and Trivex to 1.3mm CT. They only surface poly to 1.0mm if you pay extra. So the poly lens might be starting 0.2mm thicker than Trivex to begin with. With those assumptions, I laid out a test job with one eye Poly and one eye Trivex. The poly lens is 0.1mm thinner at the thickest point, but 0.1 mm thicker at the thinnest point. And the poly lens weighs more. I choose a pretty square frame...I probably could have engineered the frame to make the Trivex lens thinner everywhere.

You get the point. In this case, you'd be hard pressed to say that they poly lens was thinner. It is definitely not 10% thinner. But it would be heavier (7 grams to 6 grams = 16% heavier). Although it might be easier if you could say "Higher index of refraction = thinner lens", that's not always the case. Some ultra high index products require 1.5mm CT, depending upon the lab and whether or not they have a cushion coat. That would make the end product thicker than a slightly lower index that can be surfaced to 1.0mm CT. Higher index does not always equal thinner lenses.

I can't remember from the jobs I've seen from a couple of different labs any time trivex was thinner than poly. In fact it was to the eye noticeably thicker. Are the labs being lazy on the CT's? Is trivex harder or more expensive to surface?

Any one else down in the trenches notice this? Full disclosure- I've only done in the dozens trivex.

[oxmoon]

It's a moot point. She listened to my explanation of why thrivex would be better for her, and said she wanted poly again, because she had never heard of trivex. I wanted to say, you just did hear of it - from me, but didn't.

[bigeyejim]

I wanted to say, you just did hear of it - from me, but didn't.

I'm writing that down.