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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