Re: Polycarbonate versus High Index Plastic (1.67) lens help!

On Mon, 10 Sep 2007 06:43:49 GMT, "L. Ron Waddle" <penguincathedral@xxxxxxxxx>
wrote:

KC wrote:
Hi all,

I just picked up a new pair of glasses from Lenscrafters. They
recommended Polycarbonate because it was apparently shatterproof etc
etc. My prescription is -5 and -5.25, so I think that's fairly high.
The frames are a lot smaller, almost a 40% smaller than my old (13 yr
old) frames. Here are some of the problems I'm seeing:

Hi, your prescription is almost identical to mine. I have worn
polycarbonate for years because of the durability issue -- I ride
motorcycles and cannot accept a material for my glasses that may shatter
in the event of an accident. I do not have any of the issues that you
discuss and doubt that high-index plastic will make any difference.

I am not an eye doctor so thus cannot tell you why you're having
problems, just that it's not inherent in the polycarbonate material with
your prescription strength.

I've seen quite a bit of variability in sensitivity to chroma between eyeglass
wearers, some of it related to adaptation, some to the quality and positioning
of the optics. It sounds like your lenses were well made and positioned
properly.

However, there is a clear link (see Mo Jalie and Daniel Torgersen) between TCA
and off-axis blur, and is a function of the induced prism from the eccentric
gaze and the Abbe value of the lens. Except for some of the super Hi-index glass
lenses, Polycarbonate has the lowest Abbe value of all the Hi-index lenses
available, and as a result, performs poorly in this area when the lens power is
above about four diopters.

Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
Wauwatosa Wi.
~~~~~~~~~~~~~~~~~~
"Science is a way of trying not to fool yourself."
- Richard Feynman
.

Relevant Pages

  • Re: Polycarbonate versus High Index Plastic (1.67) lens help!
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