I have a young customer who is a -6.00 OU. He is wearing poly without AR and sees a rainbow effect in his lenses. I'm sure poly is playing a role in this. I personally think his Rx I'd too high for Trivex. Is the recommendation 1.67 with AR ? Should mention it's a spectera job
All high indices are essentially the same when it comes to chromatic aberration. He'll get used to it.
Tell him to lay off the iowaska, and remake in 1.60 w/AR!
Relax and have a homebrew!
+1 to 1.60 in this Rx. Going from poly to 1.67 with these symptoms would be liking banging you head on the table a second time. JMHOOriginally Posted by Fezz
Anything is better than Poly, though not necessarily by very much.
I would say that Trivex would work fine for the Rx in the correct frame. While it is thicker than poly due to the lower index, it's not noticably so until around -10.00 (depending on whose website you look at) and it will be lighter weight.
Other than that, I agree that 1.60 is the way to go. A/R is always good, no matter what material.
Oh, and I'm getting in ahead of Chip in saying that contacts will completely solve the problem.
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.
+1 although I would sub a Sapphire and Tonic for the Homebrew.
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A rainbow effect could be Newton rings. As there is no AR it could be some partial delamination of the hardcoat on the poly which contains some air that shows up in this color effect. Check it out.
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This effect is called birefringence and can happen in any high index material, but especially Poly, 1.67 and 1.74. Its not caused by the material alone, but by an ABBE value mismatch (over a certain %) between the hard coat and the base material. If you remember when Essilor launched 1.74 it looked terrible because 1.74 hard coat is enormously expensive and many labs were throwing 1.67 hard coat on. Essilor solved the problem by bringing much of their 1.74 production back to Texas (and now Mexico) to guarantee 1.74 gets the right coating.
There are poly's with ABBE matched hard coats, but you have to look harder. Resolutions, Zeiss and Vision Warehouse are the ones I know of (Zeiss licences from Resolutions) and there are 2 more I have seen, but can't remember the name. They will cost a little more though, so most places use the cheap poly.
Birefringence is more noticeable on flatter base curves or without AR.
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