help with frame sizing and rimless/drillmount questions

Discussion in 'Glasses' started by Kelly, Sep 27, 2005.

  1. Kelly

    Kelly Guest

    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

    (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?

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

    Thanks a lot. Partial answers welcomed. :)
    Kelly, Sep 27, 2005
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  2. 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.
    William Stacy, Sep 27, 2005
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  3. Kelly

    Kelly Guest

    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
    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
    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

    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.
    Kelly, Sep 28, 2005
  4. 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.
    William Stacy, Sep 28, 2005
  5. Kelly

    Kelly Guest

    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
    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:

    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

    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
    Kelly, Sep 29, 2005
  6. 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.
    William Stacy, Sep 29, 2005
  7. Kelly

    Kelly Guest

    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...?)
    Kelly, Sep 29, 2005
  8. That was chromatic aberration more than prism distortion, but it is very
    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
    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...

    w.stacy, o.d.
    William Stacy, Sep 29, 2005
  9. Kelly

    Kelly Guest

    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?
    Kelly, Sep 30, 2005
  10. 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.
    William Stacy, Sep 30, 2005
  11. Kelly

    Quick Guest

    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, Sep 30, 2005
  12. 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:
    William Stacy, Oct 2, 2005
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