help with frame sizing and rimless/drillmount questions

I have never worn glasses before and am having some trouble adapting.

I found the following quote:
"The rule of thumb is that the total width of the frame front all the
way across, including the endpieces, should be close to the thickness
of your head. This will allow for the optimum proportion of the frame
to the head, and for the best comfort."

(1.) Does this just imply the width across front of the forehead?
(2.) Does this rule of thumb seem like a good guide?

I'm 6' with a round face, so it is recommended I get narrow/rectangular
glasses and more round ones do look kindof silly on me.

My optician has a "replace one time" (60 day) policy if I decide to
switch frames and the deadline is fast approaching. I currently have
Ralph Lauren 1473, which is brown and has the measurement markings
50/18/130. (It also says 5/2 on the bridge?) Subjectively, I am told
by multiple people that they look good on me and do not look too small.

Right/left field of vision is ~30-45 degrees and the up/down is ~20-30
degrees. When looking straight ahead, vision is fine but I see an
outline of the frame that reminds me of looking through binoculars. At
night, the back of the frame catches lights is more distracting.

My posture and ergonomics aside, if I presently tilt my head to center
the bottom center of my 19" monitor as I type this then glance up, I
can see the top 1/3rd of my monitor above the top edge of the glasses.
I've tried to wear the glasses often, but the height of the vision
correction makes dining while talking to someone so weird that I always
want to take them off when eating.

The frames are adjusted so that they flare out slightly and the arms do
not put too much pressure on my temples.

(3.) Should I expect to adapt further? Is 45 days just not enough time
to tell?

(4.) Not many people seem to make larger frames but Silhouette does.
One of their frames goes as wide as 57 on one vender site with the
model "Titan Minimal Art". Is there any disadvantage if I just went
with the largest?

(5.) With "rimless" Silhouette, would I notice the "edge" less or more?
In other words, is the edge of the lens itself just as distracting as
a frame?

(6.) I'm having trouble finding height measurements for these on the
web. Is there a good resource?

(7.) For a given model, does lens height increase as you move to wider
frames?

(8.) With drillmount designs, would I be able to adjust the tilt just
as much as with a normal frame or not at all?

(9.) Some web sites say they require polycarbonate, which I understand
has more visual distortions. Other sites say polycarbonate or high
index but not standard plastic due to cracking. Are high index just as
good in rimless/drillmount?

(10.) If I would not be able to use standard plastic, what is the most
distortion-free high index that I could use with a drillmount? (My
perscription is not very strong so weight is less an issue but I am
easily bothered by visual distortions.)

(11.) With Silhouette specifically, I am looking at models 7508 and
7510 (links below). Would this be a good choice for me?
http://www.silhouette.com/en/products/highlights/classic_visions/models/00626/index.asp?id=6
http://www.silhouette.com/en/products/highlights/classic_visions/models/00626/index.asp?id=8

(12.) Finally, should I just stick with the ones I have now?

Thanks a lot. Partial answers welcomed.

 

The widest part of the head, which could be anywhere, depending on the
shape of the head, but usually is about at the ears.

All other things being unknown or not important, yes. The actual Rx
will bend this rule often.

45 days is more than enough. I'd never ask a person to "adapt" for more
than 1 week.

Depends on your Rx and your P.D. You should post those.

Yes, esp. if they are polished edges, they will really sparkle.

Now there's a hint about your Rx. Not enough info, tho'.

Yes, and by the same amount.

You might, but it would be better to let an expert do it.

I would never order polycarb, which are outmoded and trashy. If
rimless, get Trivex.

There are none in existence. Again, get Trivex.

Need the P.D. and Rx.

No. If you're not happy, get a remake in Trivex, as big as you want.


w.stacy, o.d.

 

Thank you very much for the reply. My responses are below.

You wouldn't even if the person had never worn glasses?

One odd thing about my perscription is that I had a strange distortion
in which things that should have been square or rectangular looked
slightly trapezoidal. I'm told this is due to differences in power and
it seems that I've adjusted to that ok. As you may expect, when I take
the glasses off I now notice the trapezoid in the opposite direction.
(In other words, with glasses I at first saw edges on the left of my
monitor as taller than the right side. Now that I've adapted somewhat,
it looks close to normal with the glasses on. However if I take them
off, the right side of the monitor now seems taller than the left
side.) No one seemed to have heard it described that way from any of
their patients at either clinic or store.

I also have had some difficulty telling when it is the reflectiveness
of the frame that bothers me, that it's small enough to always somewhat
be in my vision on all sides or if it's the slight (normal) distortion
toward the edge of the lenses. These are high-index 1.57 and they're
definitely better than the polycarbonates I had tried from another
place. They also have the "anti-glare" option.

Some background: I had originally gone to a buy-one-get-one-free place
but got discouraged when they didn't get the PD correct AND didn't
catch it when I had them check it. After, I went to a reputable
opthamologist who really seemed to know his stuff and he had an awesome
team. When he sent me to his glasses shop down the street, he never
works there of course and I only talk to the optomitrists. They are
experienced with normal people but they don't inspire confidence with
the unusual cases as I seem to be in almost every regard.

Sorry. I did not have it on me yesterday and was getting nervous about
the mentioned deadline so I hoped my questions were general enough to
not require it. Here are the numbers:
OD: -1.50 +1.25 X 160
OS: -1.25 +1.00 X 50
PD = 69.5
* The base curve is not provided, please use the base curve from the
previous pair of glasses. If this is a new perscription, please use
the optical laboratory's recommended base curve.

They measured the PD with the Empire Strikes Back binoculars looking
thing so it should be more accurate than the guess and dot with a
marker method that the buy-1-get-1-free place did. I made them
photocopy my perscription and wrote down the PD after they measured it.
Seemed like I was breaking protocol there.

So light perscription, lots of astigmatism, right? What does that mean
for me for frames?

With the assistance of a compliant coworker, our best estimate of my
head size temple to temple (flat, not bent) is between 6 and 6.25in
(152.4-158.75mm). My current glasses are 50/18 which would mean 118mm
across, right? That's a difference of ~1.5". If I measure the where
the arm is extended to where the lens begins, this seems close enough
to .75" per side. Does that all sound right to you? I have a very
round face but my lineage is German and Native American, so my head
isn't as huge as giant basketball players or anything.

If I'm on the right track, do you have any idea how to estimate what
the height would be of those Silhouette lenses so I could estimate how
much more vertical I might get from them? Sorry if this seems
obsessive but the larger model would be a special order and I only get
one shot at it. (And they will probably already be annoyed with me.)

I was tempted to see what I could do with a marks-a-lot.

I may not have worded that question very clearly. I meant to say that
I could not find the height measurements for different Silhoette frames
on their web site or on other vendors' sites.

Ok, that's a start. It'd be nice to be able to keep the "aspect ratio"
so I got a rectangular look for my round face but still got more lens
height.

I meant to ask if the drillmount designs could be tilted (by anyone).
I would definitely let them do it, but since the tilt helped some with
this pair I expect I'll want that ability.

I can't remember the brands. Which index number is Trivex? I'm so
picky I'd probably get glass if they let me. (I had some awesome Maui
Jim polarized sunglasses.... very wide and tall too. Crystal clear.)

I'm sorry if I'm using the terms incorrectly. My understanding was
that there was polycarbonate (worst for distortion), plastic (least
distortion) and varying degrees of high-index that are similar to
plastic but more durable and can be made thinner. Can you fill in the
gap?

Ok. How about now?

I know I'm a little anxious about new things and this is a bigger deal
for me than it should be. I'm trying to monitor myself and make sure
these are genuine issues so that I'm not just being a pest of a
customer.

Thank you very much for your help with this.

In response to the other poster's suggestion: the glasses slide only a
little from the highest closest position throughout the day and the
framing concerns I have still exist even after I have just pushed them
to the closest point. It does help a little, of course, if they've had
time to get nudged a little but not enough to really make a difference.
The nose fit seems right.

 

Not with full time wear. Maybe occasional wear, the less the longer
they might take, but full time wear? 1 week MAX (I'm not in the habit
of torturing my patients). Actually, my routine advice is to come back
if they're not adapted over the weekend.

Very common, especially if the astigmatism Rx is slightly off axis, or
stronger than necessary. Can be normal, but if bothersome, my modus is
to recheck axis and reduce cylinder.

Frame awareness also shouldn't take more than a few days of full time
wear to get over. Part time wear, and you may NEVER get over it. Same is
true of chromatic aberration.

....

No. Light prescription with light oblique astigmatism. P.D. is really
not a factor if they are single vision.

Try it. If you like it, you can have it professionally done if it
doesn't come out perfectly.

If you're talking a drilled rimless (no eyewire, just a bridge and
temples), you can have them size the lenses to anything you want. You
want larger, tell them larger. With your Rx, no problem, but demand
Trivex material (IMO). First have an O.D. carefully recheck that
astigmatism Rx.

I think you're talking about the "B" measurement, the maximal vertical
dimension in mm, avail. in the big FRAMES book. Again, if rimless, you
can upsize, and every mm additional horizontal ("A") measurement, you'll
get a mm vertical as well.

no problem.

You can't get glass rimless any more. Trivex is around 1.53 and has
great ABBE value.

Not very well. Just google search on "table of abbe" values or
something. The higher the ABBE number, the better, and vice-versa.

Maybe someone else will look the frames up for you, preferably someone
who has you there personally...

w.stacy, o.d.

 

It definitely took a little longer for me to adapt to the "trapezoid."
I take them off when eating, sleeping and talking with people face to
face but keep them on otherwise. Most of my time is in front of a
computer and they are always on then.

Is there a more common word to describe that effect? I'm really
surprised that it is very common yet no one seemed to understand what I
meant when I described it.

I originally saw an optometrist next door to a buy-1-get-1-free place.
This was the first time I had my vision checked in many years. This
was a very quick process and my eyes were not dilated. He wrote the
perscription and I went next door to shop for frames. The trapezoidal
problem bothered me immediately when I began looking at monitors,
paper, or anything else that was normally square or rectangular and
close up. I went back to the store to talk to the optician and he made
some adjustments that didn't seem to do much, then checked the optical
center and said it was fine. I then went back to the optometrist and
he spent more time with me. He checked the glasses and immediately
said the optical center was off. He then sat with me and constructed
some makeshift goggle glasses using an errector set looking collection
of lenses in a drawer. This time he found my eyes to be very slightly
worse than originally found. However, he said that if I was having
trouble adapting that I could still try a slightly weaker perscription.
When I looked through the makeshift glasses, however, the trapezoidal
effect was just as bad but the letters were not quite as crisp. He
wrote this very slightly weaker perscription for me but I was not
really content.

On a recommendation, I then saw an opthamologist who had an entire team
of really sharp people working in a sort of assembly line. One person
would dilate my eyes, another would show me slides. The part the
doctor did himself involved shining bright lights into my pupils, which
I assume was to look for signs of disease and to talk with me a little
about my complaints of dry, itchy eyes which I really did have but
bringing it up caused the visit to fall under my insurance coverage.
The slides test was more thorough at this place but the perscription
was very similar to the stronger perscription that the optometrist had
measured on my return visit to him. I tried to explain the trapezoidal
effect to my doctor but as I said, no one really seemed to be able to
relate to my description. He asked to see my glasses and also found
the optical center to be off. He also said the glasses were not nearly
large enough for the size and shape of my face.

He then recommended that I visit a "real" optical shop, which he just
so happened to own one of. He said, "Even there, you will only find a
handful of frames that will be right for your size and shape but
they'll be able to help you with that better there." This makes me
think that the doctor and his opticians were not really on the same
page about sizing. The optician showed me several frames that were
mostly 18-20/49-50. As you know, these are fairly common sizes and not
really much larger at all than the previous frame that the doctor had
condemned. The doctor said it was important to get my pupils near the
center of the lens and admittedly, these frames do achieve that more.
If I get wider lenses than this for a wider frame, that will be
probably be less true.

I believe the perscription is accurate in that this perscription yields
the sharpest text/best focus. If it could be off in some other way,
I'm not sure what to look for.

This is very contrary to what the opticians at the shop had to say.
They said, "Some people never get used to it and always hate wearing
glasses." As you can imagine, this was a somewhat frustrating response
for me. When I described how I felt, they said that if it was the
frames that bothered me they could do the exchange once as long as it
was within 60 days as that's what their agreement with the lab is. (I
suddenly felt more foolish for going to the doctor's shop when I found
out they were outsourcing the lens making anyway.) They said that if
it was just peripherally looking through the edge of the lens that some
distortion there is normal and that a larger lens would only make that
worse.

The opthamologist had emphasized the importance of optical center.
Does this mean the same thing? Do you think he was wrong to say this
with my perscription?

The Silhouettes I'm looking at are drill-mounted. They only have
titanium flexible temples and a bridge.

I remember the optician saying they could do different styles of the
Silhoettes in other sizes but that I would not be able to purchase the
matching tint clip if it wasn't a size they offered. I didn't realize
she must have meant that they could actually make them to any size.

If I do get larger frames lenses that give me more peripheral on the
left and right outside, my eyes will be closer to the inside edge of
the lens than the outside edge of lens. With my perscription, will the
distortion resulting from not looking through the center of the lens be
noticable? Am I misunderstanding the manufacturing process? Is *this*
the point of the "optical center"?

I found this chart: http://www.krspecs.com/abbe.html

In that chart, the Sola 1.53 actually has a higher abbe value than
Trivex (47 compared with 43). I doubt I will have a choice in this
anyway, though. I'm sure they will only offer one brand at a given
index value. I will ask, though. If this Sola is available, is there
any reason not to take it over the Trivex?

Also, I can't help but notice that the Trivex has a specific gravity of
1.11, which is much lighter than any of the others. How is it that
Trivex is thicker than the others but still lighter? ("Space
technology?")

I doubt this effects me. My perscription is so light that weight
probably isn't a factor and the Sola 1.53 is only slightly heavier at
1.21. It's just curious.

I have looked at the Silhouettes (and every other frame they carry that
is in a somewhat larger size) in the store. What I'm asking here is
only the mechanics, not the aesthetics.

Am I understanding correctly:
*The edge of a drill-mount will be less noticeable than a plastic or
metal reflective frame.
* A drill-mount can be made in any size. The shape of the lens will be
the same at any size as both dimensions are increased at the same rate.
* If I measure the width of my head from temple to temple, this number
should approximately match: eye size * 2 + bridge.

Thanks again for your replies. It is very satisfying to begin to
understand this. The topic was foreign to me and I'm never content to
treat something I'm spending a lot of time and money with as a black
box.

 

Trapezoid effect is perfect, but not everyone seems to have paid
attention in elementary geometry.
Shape distortion would be another way, but I like trapezoid better due
to the specificity.

(snipped a lot of dr/shop comparing...)

Usually it is, but if they are single vision, your powers in the
meridians that count (180 degree, horizontal), are almost zero, so
unless they accidentally grind in some prism, the location of the
optical centers is pretty trivial.

That's true. Your clips would be a loss.

In your Rx, it's really not a problem, the amount of induced prism being
near zero. The higher the power, the more significant displacement of
the optical centers become. Put another way, if you consider a zero
power lens, the optical center is not defined; that is, you could
"decenter it" all the way to china and it wouldn't induce ANY prism.

For drill mounts you want the strength of Trivex which is orders of
magnitude better in that dept. The abbe difference is not significant.

Lower specific gravity, and yes, a result of resin research.

Maybe. Since it's flat-beveled and often polished, it can often be MORE
noticeable. This can be minimized with a variety of edge treatments.

True, within reason.

Not quite. Add in the size of the endpieces, which usually stick out a
bit from the outsides of the lenses.

w.stacy, o.d.

 

P.D. is really not a factor if they are single vision.

The first glasses I had were polycarbonate and there definitely was
some prism distortion. Maybe this is why he said it, but he could have
as easily suggested another lens material.

That makes sense to me--I only thought the high cylindrical and axis
numbers might make the optical center more important.

I'll hope they can do Trivex, then. If not, is the Sola 1.53 not the
best alternative? Next down the list would be Hoya 1.56, which I think
may be what I have now in the existing frame.

I was afraid of something like that. One web site vendor offered and
edge treatment. If the shop I've purchased from doesn't, is this
something I can do myself?

The endpieces are usually adjustable, aren't they? The frame I have
now does not put too much pressure on the sides of my head, the ends
are just angled outward slightly.

A couple other things I thought to ask:
Is there a significant quality difference between brands of AR coating?
They had a couple of options there but they didn't offer much opinion
on them.

I don't need any other coating for this type of lens, right? (It should
already be scratch resistant and UV blocking enough...?)

 

That was chromatic aberration more than prism distortion, but it is very
similar.

It's a bit complex, but since you're persisting, here it is: the power
of the lens varies smoothly from meridian to meridian around the
lens,from the sphere power AT the axis of the astigmatism to the
algebraic sum of sphere and cylinder powers AT the opposite meridian (90
degrees away from the axis). That's why I say your powers are near zero
at the 180 meridians (the horizontal). The closer the power to zero at
180, the less important the OCs become, since prism power equals power
(at 180) times the decentration in cm, with the resultant being in prism
diopters.

No problem except for the drilling part. Anything but TRIVEX is prone to
breakage at the drill points, (or "starring" in the case of polycarb).

Make sure you get the best avail. for the material you choose. In the
case of Hoya Trivex, it's Super High Vision AR coat. And make sure it
has a redo warranty if it scratches...

Right.

w.stacy, o.d.

 

Thanks for the explanations. Was the edge treatment on the
drill-mounts something I can do myself if it's not something the shop
I've purchased from can offer?

 

Sure, you can "paint" them, if you're fairly careful. There are special
felt tip pens used in the profession for this, but you have to be very
careful to do it right, get it uniform, and try to keep it off the
polished/molded surfaces. Good luck.

w.stacy, o.d.

 

What about lightly sanding with super fine grit sand
paper to dull the surface? I would expect it to be easier
to get uniform than "painting" with less chance of a
whoopsie into unwanted areas.

-Quick

 

Maybe, but why not let the lab do it? Unless you got lots of free time
and/or just like to tinker, the price is probably worth it. And if
there's a whoopsie, they pay for it. But sanding, sure why not?

w.stacy, o.d.

Quick wrote: