I just ran the numbers you gave, and approximate the edge thickness.
(Though I did have to assume a few values, like PD and bridge
dimension)
I couldn't get to a 6mm edge thickness, in any of the materials. The
thickest I could calculate was 5.3mm, and that assumes that your
pupils are unusually far apart.
Using your values, supplemented with a 19mm bridge, and a 63mm PD, I
get the following numbers:
CR39 (clear resin) = 4.8mm edge thickness
Polycarbonate 1.56 = 3.9mm
1.67 high index = 3.5mm
Lantal 1.9 = 3.0mm
Hopefully this helps you out.
-- Chuck Knight
On Tue, Oct 13, 2009 at 1:22 PM, Chuck Knight <[email protected]> wrote:
> Hi, I'm Chuck Knight. :-)
>
> The edge thickness calculator is a very handy tool. It'll estimate
> the thickness of the lens edges for you. So, let's start by
> discussing the high index options.
>
> High index lenses. You have such a mild prescription that I can't
> believe that they recommended "high index" lenses. The difference
> between poly (the standard at most of the online stores, having an
> index of around 1.56) and the high index materials usually results in
> a reduction in thickness of around 10% or so. As our friend, above,
> said...his Zenni glasses (poly, index 1.56) are quite thin.
>
> On a 6mm thick lens, a 10% difference represents just over 1/2mm. Is
> it worth the difference in price? Only you can decide. My
> fingernails are just about 1/2mm thick.
>
> Now...your other questions involved ruggedness and optical quality.
> Let's address them individually.
>
> Ruggedness. The most rugged glasses have a full frame. This supports
> and protects the lens, to the maximum amount possible. If ruggedness
> is your sole requirement, don't go rimless.
>
> But, having said that, many MANY people wear rimless on a regular
> basis, and have no problems. It's just that any glasses made such
> that the lens is a structural part, will be inherently less rugged.
>
> Optical quality. Each possible lens material, be it CR39,
> polycarbonate, trivex, or any of the others, has its own unique
> optical properties. The "clarity" of the lens is measured by
> something called an ABBE value. CR39 has the best optical qualities,
> but results in the thickest lenses. Trivex has the next best quality,
> and results in the thinnest lenses.
>
> Polycarbonate has the worst optical properties of the 3...but many of
> us wear them with no problems, whatsoever. Poly's properties also
> include toughness, so it's ideal for rimless glasses.
>
> I'll go out on a limb, here, and say that if you tried the default
> poly option on a cheap pair of glasses, just as a first attempt, that
> you would be delighted with the results. You can try online glasses
> for *literally* just a few dollars. Since Zenni was mentioned, their
> options begin at only $8. Coastal Contacts' options start at $6.95!
> No rimless at the $8 level, though.
>
> Since you have a kid, you might consider this an experiment...and keep
> the first pair as a backup. Once glasses no longer have to cost
> $400/pair, it's not unreasonable to have multiple pairs on hand!
>
> -- Chuck Knight
>
>
>
>
>
> On Tue, Oct 13, 2009 at 11:56 AM, powrwrap <[email protected]> wrote:
>>
>>> On Oct 12, 8:28 pm, "Rob O." <[email protected]> wrote:
>>> I'm about to venture in to this uncharted (for me) territory of
>>> purchasing eyeglasses online. I'm tempted to try a pair of rimless -
>>> which would also be a first for me - but a little nervous about the
>>> edge thickness of the lens.
>>>
>>> In my current glasses which came from a brick & mortar shop, the left
>>> lens (-2.50 spherical, -1.50 cylindrical, & 160 axis) is about 53mm
>>> wide & 27mm tall. At its outer-most edge, the lens is 6mm thick. I
>>> have no idea what the lens index is specifically, although I recall at
>>> the time of purchase, that I had to pay a bit extra and wait a couple
>>> of days for "High Index" lens.
>>>
>>> I'm comfortable with a comparable lens width (+/- a couple of mms) but
>>> I worry that in a rimless style, that's 6mm outer edge would look
>>> kinda bad. So, would stepping up to a more expensive 1.591 or 1.60
>>> High Index lens keep that outer edge thickness down a bit? And aside
>>> from the cost, is there a downside to using a higher index lens - do
>>> you forgo some material strength or scratch-resistance when you get
>>> into those higher index options? I read something that implied that
>>> higher index lens might be less optically-correct than standard index
>>> lens - any truth to that?
>>
>> Chuck Knight, a frequent poster here, uses this website to help
>> determine lens edge thickness:
>>
>> http://www.opticampus.com/tools/thickness.php
>>
>> My prescription is -1.50 spherical and I just measured the edge
>> thickness of my Zenni polycarbonate rimless lenses with a micrometer
>> and they are 2.5mm thick.
>>
>> I can't answer your questions regarding high index lenses, but I'm
>> sure someone will.
>>
>>> And finally & more generally, I'm a new Dad and my glasses are taking
>>> a bit more incidental abuse from my rough & tumble toddler. With that
>>> in mind, am I just crazy for even considering rimless? Would a hinge-
>>> less design be better or worse for enduring minor bumps?
>>
>> Rimless glasses are a bit more fragile than other style of frames, but
>> with care they can last a long time. I would think a full 180 degree
>> spring frame would be better than a hingeless design.
>>
>> Are these progressives? (Doesn't sound like it). If they are single
>> vision lenses you could give Zenni a try and probably get a nice
>> rimless design for less than $30. If they break you're not out a
>> bundle of money.
>> >>
>>
>
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