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Thread: Mid Index and UV Resistance

  1. #1
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    Mid Index and UV Resistance

    I keep finding conflicting information on mid index 1.56 lenses. Do they need UV coating or do they absorb some UV without additional treatment?

    Thanks for any info!

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    Master OptiBoarder OptiBoard Gold Supporter
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    Some do, Some don't, Use Trivex.

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    OptiBoard Professional RT's Avatar
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    As Tallboy indicated, "1.56" is merely an index of refraction and does not uniquely identify a particular lens material nor any other property other than index of refraction. There are several different types of chemistry involved with lenses whose index of refraction rounds to 1.56. You'd need to know what lens your lab is providing in order to understand the specs related to UV, impact resistance, Abbe value, etc.

    The urethane based 1.56 material used in BluTech lenses, for example, is extremely impact resistant whereas the thermoset material used in older 1.56 index products has much lower impact resistance.
    RT

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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  5. #5
    sub specie aeternitatis Pete Hanlin's Avatar
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    As RT pointed out, it somewhat depends on the 1.56 monomer being used. (Side note, I often see CR-39 used to describe 1.50 plastic lenses, but in fact there are many different monomers used for 1.50 lenses, CR-39 is just one of them.)

    It seems like 1.56 has always found something to keep itself around and relevant. Long ago, (if I recall correctly) there was a Transitions generation that came out in 1.56 quite a bit earlier than in any other material, because for some reason a property of 1.56 allows for better photochromic activation.

    Later- and more relevant to this thread- 1.56 saw a boost in popularity with laboratories because it can be UV cured (which opens all kinds of possibilities for in-lab casting). Most lens materials are either thermoset or thermocure, so a material that can be cured with a UV light is pretty handy. The UV cured 1.56 blocks UV light naturally (after all, it's the absorption of the UV that cause it to solidify in the first place, and it continues to do so afterwards).

    Personally, I'd rather use a 1.60 lens over 1.56- but yes, 1.56 does block UV.
    Pete Hanlin, ABOM
    Vice President Professional Services
    Essilor of America

    http://linkedin.com/in/pete-hanlin-72a3a74

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    Yeah pete I use 1.60 and trivex interchangeably, same charge to my customers. They both will usually get the job done, once in a while there is a reason to use one over the other imho.

    Post more often hombre

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