Results 1 to 6 of 6

Thread: Mid Index and UV Resistance

  1. #1
    OptiBoard Novice
    Join Date
    Jul 2015
    Location
    Virginia
    Occupation
    Dispensing Optician
    Posts
    5

    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!

  2. #2
    Master OptiBoarder OptiBoard Silver Supporter
    Join Date
    Mar 2012
    Location
    Maryland
    Occupation
    Dispensing Optician
    Posts
    1,429
    Some do, Some don't, Use Trivex.

  3. #3
    OptiBoard Professional OptiBoard Silver Supporter RT's Avatar
    Join Date
    Feb 2001
    Location
    CT
    Occupation
    Lens Manufacturer
    Posts
    868
    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

  4. #4
    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
    Join Date
    Dec 2004
    Location
    At a position without dimension...
    Occupation
    Dispensing Optician
    Posts
    4,118

  5. #5
    sub specie aeternitas Pete Hanlin's Avatar
    Join Date
    May 2000
    Location
    Hickory Creek, TX
    Occupation
    Lens Manufacturer
    Posts
    4,914
    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
    Director Technical Marketing
    Essilor of America

  6. #6
    Master OptiBoarder OptiBoard Silver Supporter
    Join Date
    Mar 2012
    Location
    Maryland
    Occupation
    Dispensing Optician
    Posts
    1,429
    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

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Trivex vs Hi Index scratch resistance
    By sdgibbs in forum General Optics and Eyecare Discussion Forum
    Replies: 1
    Last Post: 02-14-2016, 11:20 AM
  2. Is Trivex Mid-Index?
    By harry888 in forum General Optics and Eyecare Discussion Forum
    Replies: 22
    Last Post: 02-09-2010, 12:41 PM
  3. Mid Index
    By chip anderson in forum General Optics and Eyecare Discussion Forum
    Replies: 5
    Last Post: 12-12-2008, 10:07 PM
  4. mid- and hi- index lenses
    By coda in forum General Optics and Eyecare Discussion Forum
    Replies: 4
    Last Post: 08-04-2004, 06:23 PM
  5. impact resistance of mid- and high-index plastic
    By yzf-r1 in forum Ophthalmic Optics
    Replies: 10
    Last Post: 05-11-2004, 06:26 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
OptiBoard is proudly sponsored by:
Younger Optics, Carl Zeiss Vision Inc., Vision Equipment, Optitech USA and The Optical Group