Thanks for posting this link. I'm going to use this a lot.

On May 4, 9:28 pm, Chuck Knight <[email protected]> wrote:
> Your sphere isn't particularly strong...your astigmatism isn't too bad.  All
> in all, a very "ordinary" prescription, judging by what we deal with on this
> list.
>
> So, let's deal with your other question...lens thickness.  Index is a term
> referring to the refractive index of the lens material...higher numbers make
> for thinner lenses.  The difference is most noticeable in thick/strong
> lenses.  BUT, the difference on a relatively normal prescription isn't that
> enormous.  Usually it's a difference of around 10-20%.  On a lens that's an
> inch thick, it's enormously noticeable...  Yours aren't that strong.
>
> There's a lens thickness calculator that we usually refer people to, so they
> can see the differences in their *own* prescription, themselves.  Let me
> find that URL in the list 
> archives...http://www.opticampus.com/tools/thickness.php
>
> Also, be aware that most of the online places use "medium index" lens
> materials, like polycarbonate, by default...it's not considered an upgrade,
> where we shop.
>
> So, shop around.  At these online prices, you can *have some fun* with your
> frames.  Some of the places sell them for $7 or $8 a pair!  Historically, I
> always chose modest wire rimmed frames, until I finally chose some bold
> plastic ones.  Why?  because I'd never had plastic, before.
>
> Turns out, that they look good on me!  I've never received so many
> compliments on any other "accessory."
>
>      -- Chuck Knight
>
> P.S.  BE SURE to get an accurate PD measurement.  It's the key to success
> with online glasses, and the one part of the prescription that your doctor
> *may* give you trouble with.  We've many discussions about this, and even a
> few sample "scripts" of how to handle a difficult doctor, or where else to
> go to get it measured.
>
>
>
> On Mon, May 4, 2009 at 12:13 PM, PghGuy <[email protected]> wrote:
>
> > I'm doing research for purchasing glasses online.  I last got glasses
> > eight years ago (I know, too long) and am only now becoming familiar
> > with the options for lenses and frames that are available.  I also
> > don't know how much this prescription differs from my last one since I
> > went to a different optometrist and don't have the last prescription
> > with me.  Given my prescription, would lens upgrades such as
> > polycarbonate or high index be a good idea to reduce the thickness or
> > would it be okay to go with the lowest plastic offered?  At the moment
> > I have polycarbonate lenses and they are adequately thin.  I read that
> > high index is recommended for a prescription of -5.00 or higher but
> > mine isn't quite that high.  I'll be getting metal frames with lenses
> > perhaps 46-48mm in width and probably under 38mm in height.
>
> > OD--Sphere:  -3.50; Cylinder:  -0.75; Axis:  136
> > OS--Sphere:  -3.00: Cylinder:  -1.25; Axis:  074
>
> > Would you consider this a "strong" or "abnormal" prescription in any
> > way?
>
> > Any advice would be appreciated.  Thanks a lot!- Hide quoted text -
>
> - Show quoted text -

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