Height of glasses lenses affects head position

Discussion in 'Glasses' started by Reece, Jul 19, 2005.

  1. Reece

    Reece Guest

    I went from a taller pair of glasses lenses to a more stylish shorter pair
    of lenses about a year ago. It wasn't until I starting taking a class where
    posture was a part of the exercises that I noticed that these new glasses
    made me point my head down to see, because when I try to look down, I run
    out of lense to look through if I don't face my head down. Short lenses
    cause unnatural forcing of the head down, because it makes your head the
    pointer of where you are looking to a much greater extent than your eyes,
    since you have to point the lenses at what you are looking at. Larger
    lenses are not that way.

    When my head was facing forward at the horizon my old glasses allowed me to
    see 45.8 degrees below the horizon, whereas my new glasses only allow me to
    see 27.4 degrees below the horizon. So to capture the same visual field as
    with my old glasses, I have to tilt my head 18.4 degrees. So about 40% of
    my lower visual field is lost with my new glasses, unless I face my head
    down, relative to my old glasses. So I am going back to my old glasses,
    where the perscription is virtually the same, and will just wear my new
    glasses for public appearances.

    So keep this in mind when you look at styles of glasses. If your glasses
    makes you keep your head off balance, that throws your posture off balance.

    Reece
     
    Reece, Jul 19, 2005
    #1
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  2. Reece

    dumbstruck Guest

    Another thing that helps is if the frames tilt the lenses down a bit
    rather than the too common flat angle as if you were typically looking
    at the horizon or above. People commonly look slightly down to avoid
    tripping, and the eyebrow is a sunshade that makes it awkward to look
    up. A down tilted lense nestles in your face geometry to give a wider
    vertical range even with a lense of poor height. So with frame choices
    so biased by these flat angled beasts, I sometimes just bend the thing
    (tricky, and no good for titanium, plastic, or valuable frames).

    Also it can be so hard to get glasses with wide field of view. I
    wonder how many people are maimed or killed by drivers who have less
    peripheral vision with stylish frames. You need instant peripheral
    vision to check before changing lanes, and many have just given up
    turning their head (further) to back up and may mow down toddlers they
    can't see in the little rear view mirror.

    Again you can bend the frame to give a slight wraparound effect, like
    the "pilot" glasses of years past. Some may argue overdoing this will
    distort your forward vision, but for active outdoor activities much of
    your vision is to the side by one eye only. Current flat lenses
    distort such side vision, so I think a little canting is likely a wise
    tradeoff for some.
     
    dumbstruck, Jul 19, 2005
    #2
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  3. dumbstruck wrote:
    A down tilted lense nestles in your face geometry to give a wider
    I think you mean a lens that has an increased pantoscopic tilt, and with
    that I agree, although someone skilled in adjusting frames who has the
    proper tools can easily adjust this angle in almost any frame.
    Now I agree with the last part about having to turn your head farther
    with smaller frames, but it's probably good exercise, as in yoga. For
    the first part of the above paragraph, I totally disagree with this
    notion for the following reasons:

    Peripheral vision does not need to be in focus to do it's job: detect
    movement and moving objects early. Extreme peripheral vision has worse
    than 20/400 form or shape vision, so it doesn't matter how high your
    vision correction is, you don't need it for peripheral.

    Now if you accept that premise, the next logical conclusion is that
    smaller frames are better for peripheral vision than larger ones. Why,
    you ask incredulously? Because the arcuate scotoma produced by lens
    edge and frame eyewire is always larger in the larger frames, covering a
    larger area of your periphery, thereby more easily covering up a moving
    object over a larger area of your periphery.

    Since nobody else seems to have made this observation before me, I'm
    claiming to be first and hereby dubbing it the "Smaller Wires Allow More
    Periphery", which can be shortened to the SWAMP theory.

    w.stacy, o.d.
     
    William Stacy, Jul 19, 2005
    #3
  4. Reece

    Dr Judy Guest

    Actually, besides frame size your prescription will affect how you hold your
    head. With larger prescriptions (over 3-4 D), the lens periphery will
    contain noticable distortions and most glasses wearers will tilt their heads
    to maintain fixation through the centre of the lens and avoid the
    distortions, large frame or small.

    Dr Judy
     
    Dr Judy, Jul 20, 2005
    #4
  5. Reece

    dumbstruck Guest

    Now I agree with the last part about having to turn your head farther
    With age it can get much harder to turn your head. Take a ride with a
    typical caddy driver in FL trying to park or change lanes - scary.
    They will concede loss of ability to find what goes on to side and
    behind. Made worse by the current styles of narrow glasses, esp
    limited for those with wide faces.
    Theory, theory, but let's talk about practical life. If that patch of
    fuzz in your periphery is a vehicle you need to know it's speed and
    direction. After looking carefully then committing to changing a lane
    or crossing the street, you may be menaced from either direction in an
    instant by a speeder. No longer any time to rubberneck, now I find
    myself completely vulnerable with the narrow frames, whereas the old
    wraparound types would let me lock on to a clear image 90 degrees to
    either side with only a tiny quick movement. For a wide face, it seems
    90% of current frames give this problem.

    P.S. Another hidden source of maiming and death that is needless result
    of style probably has no remedy for the vision customer. The rearview
    mirrors of cars are becoming no longer adjustable for their location,
    just their tilt. For a tall driver this is directly in the way, and
    you may as well paint the central quarter of the windshield black from
    top to bottom!
     
    dumbstruck, Jul 20, 2005
    #5
  6. dumbstruck wrote:
    let's talk about practical life. If that patch of
    You can't tell any more about its speed and direction if it's in focus
    rather than out of focus when relying on your peripheral vision. There
    is no difference.

    After looking carefully then committing to changing a lane
    It is NOT the "problem" of a small frame. As I pointed out in my other
    post, larger frames just move the blind area caused by lens edge and
    frame eyewire farther back and make it LARGER, thus obscuring a larger
    object. But then if you really believe you'll see better with a larger
    frame, they are still widely available, up to huge sizes.
    You could remove it completely and rely totally on your side mirrors,
    like all the truckers have to do, or replace it with a smaller mirror
    placed wherever you like. But then you are exaggerating the size of the
    mirror. It's really less than 5% of the area of the windshield, not 25%.

    w.stacy, o.d.
     
    William Stacy, Jul 21, 2005
    #6
  7. Reece

    dumbstruck Guest

    I'm not talking about LEAVING it in peripheral; naturally you turn
    almost 45 degrees to either see your potential assassin thru your wide
    frames, or just a patch of ambigous fuzz just outside your narrow
    frames. It's not a theoretical debate but something I live every other
    day or so, when circumstances lead me to switch to narrow frames to
    walk thru some crosswalks. It is undoubtedly a magnitude or so more
    dangerous, with you having to scan 180 degrees at once to see if
    drivers will run the walk light or are just playing chicken. With
    narrow frames you can no longer keep all in sharp view in split
    seconds required. Maybe the 180 case is less critical for drivers.
    Not concerned with that blindspot which is small enough (with thin
    lenses and frame) to be erased by slight movements of the head or
    scene. I don't see hardly any wide frames avail where I shop, except
    for freak versions with enormous height. While these may be avail in
    some areas, many may be restricted to a little HMO shop for instance.
    Not on rentals or shared cars. Side mirrors have bad blind spots which
    is why truckers tend to have them stuck way out. Mirror look hard to
    substitute, but maybe I have to look more into this. What a tall
    person actually has to do is rotate the mirror clockwise about 30
    degrees or whatever it takes to lift the close edge up out of view
    (except when the road dips).
    The mirror can be almost a foot wide; that would make your windshield
    20 feet wide! Oh, you didn't accept the notion that it effectively
    blocks 100% top to bottom. And the mirror is turned to you; look at
    the angular percentage from left windshield edge to about an equal
    angle to the right, where almost all action happens - that would be
    more than a quarter obscured.

    I'm not making this up - it just takes moments to have a near accident
    in these cases where you don't take action on the mirror. You can't
    see folks pulling in front of you from the right hand side, or even
    cars ahead either coming or going, given wanders and dips in the road.
    I hope folks will listen to what I'm trying to say rather than picking
    literal nits since I don't have time to bulletproof these posts for
    every possible shade of interpretation.
     
    dumbstruck, Jul 21, 2005
    #7
  8. dumbstruck wrote:

    OK in that case, I'd agree you have a *slight* advantage to a large
    frame over a small one, but it's slight because a large frame usually
    means about 56 mm eyesize vs a 48 or 50 mm eyesize, only 6 or 8 mm total
    difference, which means only 3 or 4 mm of additional temporal lens
    width. This may seem to be a lot of lens area, but it really means that
    a 4 mm additional head turn would accomplish the same thing. Now some
    people have such restricted neck flexibility as to make even a 4 mm
    movement tough, but not many. Hence your complaint is rarely heard, and
    I've fit thousands of large and thousands of small frames. By far most
    people would never go back to the big old styles because of the less
    weight, the better peripheral vision I spoke of earlier (which becomes
    even better with higher power lenses), and the better cosmetic effect.

    w.stacy, o.d.
     
    William Stacy, Jul 21, 2005
    #8
  9. Reece

    dumbstruck Guest

    Not talking lense area but max extent beyond a (wide) pd. Wide bridges
    a help. Narrow frames may box in wide set eyes so they have hardly any
    outward view at all, esp if frames slid a bit down the nose in heat of
    use. A small extension of frame width can mean a huge percent increase
    in angular view.
    Neck flexibility needn't be an issue. Cross a street in my
    neighborhood. Even with a walklight you will be simultaneously
    approached by both sides by speeding SUVs. Some show signs of seeing
    the stoplight, but many rely on a last minute panic stop. A fair
    proportion just blow thru the light due to inattention or DUI (yes
    there are many accidents). You have to track these latter two and
    prepare to dive out of their way with quick glances to either side with
    no time for significant neck rotation, since turning one way slows down
    your response to action on the other side. And can be annoying in
    other situations...
    I think it is a step forward to reduce the excessive heights, although
    this is frequently overdone. But the width, at least for wide pupilary
    distance (64+?) has gotten so narrow it is ridiculous. I think a lot
    of folks just don't care if they are an accident waiting to happen;
    just wanna look good yakking into their cell phone and willing to pull
    the occasional tricycle wreckage out of their bumper at the end of a
    day.
     
    dumbstruck, Jul 21, 2005
    #9
  10. Reece

    Quick Guest

    But wide frames aren't going to fit inside the crash
    helmet you should be wearing when you go outside
    right?

    -Quick
     
    Quick, Jul 21, 2005
    #10
  11. I was about to suggest contact lenses, but your most astute observation
    trumped me completely...

    w.stacy, o.d.
     
    William Stacy, Jul 21, 2005
    #11
  12. Reece

    dumbstruck Guest

    But wide frames aren't going to fit inside the crash
    Don't get me started on how those full face, tinted visor helmets
    restrict vision <g>! I actually have tended toward the most minimal
    helmets when required. But my long, safe participation in probably the
    most dangerous of airsports may have made me safety-fussy, as many
    aquaintences have been maimed or killed in it over the years.

    And before yesterday I might have admitted being obsessive in seeking
    the rare diving goggles that don't block side vision. But see this
    account of a diver yesterday being impaled by a barracuda, leaving him
    on a respirator with possibly a destroyed liver. Based on the friends
    description of the fish taking a sharp turn before striking, I could
    guess that problem was not enough warning due to TOO NARROW GOGGLE
    FRAMES <g> http://starbulletin.com/2005/07/23/news/index3.html

    I guess you have to suspect that a sole pleader on such an issue being
    either a crank with poor judgement... or someone with heightened
    perceptiveness or experience. In this case I gradually became aware
    that the closest intersection I use from here has frequent T-bone
    crashes, I can even hear them every few days from where I am typing -
    sometimes a squealling near miss, but often with a wump and ambulances
    doing the cleanup.

    Since I've lost a family member due to t-bone elsewhere, I took a
    closer look. The incredible thing is that about 10% of folks blew thru
    the red light (the middle, not near yellow or green) if no car or
    person is visibly crossing the other way. I had almost been run over
    crossing from time to time, and now realized it wasn't my fault. There
    were various reasons that the drivers didn't tend to see this as a
    controlled intersection, or even an intersection at all. Another
    intersection I use often also had these quirks in spades.

    Some of us wacko safety nuts have helped a lot with lengthy efforts. A
    building overlooking crash-central campaigned for redundant stoplights
    there. I campaigned for repainting the 90% faded crosswalks, and
    hooked up with a legislator who showed there was some dirty business
    leading the city to buy instantly fading paint. Best help was just the
    luck of upgrading to LED stoplights which gets more attention.

    But still is dangerous due to escalation of meth-DUI and so on, so my
    axe to grind is these narrow glasses that put pedestrians (and sport
    players, etc?) at such a disadvantage. Wish I could take my own advice
    and just trash them, but they're now my expendable pair used for
    certain cases where they may be lost or damaged (not driving). Anyway,
    now any consumer that has tremendous tolerance for tedious reading is
    duly warned that pitfalls exist in those apparently friendly optics
    shops selling evil but stylish tiny specs <g>.
     
    dumbstruck, Jul 23, 2005
    #12
  13. Reece

    dumbstruck Guest

    Even several re-reads of your posts leave me baffled why you say that.

    Just stand still in the corner of a square room, keeping your head
    looking parallel to one wall. Then move just your eyes to seek the
    opposite corner of the room at 45 degrees. With my smaller frames this
    is just barely within the zone of clarity, which is a disaster! I'm
    not concerned about the slight occlusion of view by the eyerim,
    although I know that a high cyl that fattens the outer edge of wide
    lenses can be esp nasty.

    Larger, and pilot type glasses go maybe 60 degrees (esp when canted
    out) to either side before ended by the eyerim. I can't focus on the
    eyerim because it's too close, but I can easily rotate eyes in long
    distance focus up to that angle. This represents an angle beyond head
    rotation where you can see (imagine criticality of this for close
    formation flying, for instance). Or looking ahead this means small
    glasses give me about 90 degree cone of vision without turning head,
    and others 120.

    One caveat is that small frames can give wide vision if set closer to
    the eyes (or if canted). Maybe my experience is warped by the very
    fact of most frames nowdays being apparently sized for elves, so they
    don't nestle into the eyesockets as intended for a large person whose
    nose fills up bridge space. I guess I'll try to mash the fit around
    nose and cant them a bit.

    Seems to me we used to pick a style, then we would pick large, medium,
    or small subtype. Now manufacturers seem to all try to target the
    youth or female market that does the most repurchases, and leave only a
    few freak styles for the big galoots. Well, thanks for your valiant
    attempts as usual to clear the issue up, although we can't seem to get
    on the same wavelength...
     
    dumbstruck, Jul 28, 2005
    #13
  14. dumbstruck wrote:

    Zone of clarity? What is that? If you do the above, your line of
    sight will not be able to even REACH the eyewire edge, unless you have
    superhuman versional ability or are some kind of iguana. I never said
    the ridiculous notion that you could FOCUS on the eyewire. I said you
    could not fixate on it, which means direct your maculas toward it.
    Obviously it would be out of focus.

    w.stacy, o.d.
     
    William Stacy, Jul 28, 2005
    #14
  15. Reece

    dumbstruck Guest

    Zone of clarity? What is that? If you do the above, your line of
    How on earth can we disagree on this? I am no iguana in being able to
    rotate eyes 45 degrees to side and more, and neither is this women
    pictured looking well more than that angle in
    http://www.istockphoto.com/file_closeup/people/men_and_women/326032_girl_looking_aside.php?id=326032

    Almost no modern glasses frame can support the angle she is looking.
    Reminds me of the sight of my mayor on TV. I think he is like me in
    having unusually wide PD, but he wears the most ridiculous little
    glasses with a frame hardly wider than his PD. Just talking straight
    into the camara you almost lose eye contact with slight head movement
    since he has such a narrow horizontal angle where the eye can intercept
    light thru a lense rather than plain air.

    Let's go thru some numbers. Earlier you said
    Let's say you have a PD of 64 with 18 of that taken up by eyeframe
    bridge, giving 56 remaining over lense area. So half of that 56 on
    either side puts a pupil in the center of a 56 wide lense; not bad with
    28 left over either side. You could figure the angle of outward view
    by some trig (cotangent table?) if you divide that 28 by the distance
    of lense from the center of rotation of the eyeball (deep center of
    sphere).

    But shrinking the lense width to 48 gives just 20 left outboard of the
    pupils in the lense, and I'm guessing a typical lense is about 20 from
    center of eyeball sphere which gives a tightening 45 degree field of
    clear view. And with a wider PD, this angle shrinkage gets
    exponential-ish-ly pathological.

    So back to the original overall point. Yes, short glasses height can
    be limiting to field of view (requiring you to tip head). You can make
    the same point for narrow glasses frame width, but there is a hidden
    dysfunctional twist. For wide PD folks, who are less and less
    accomodated nowdays, the narrow frames just give you an imploding field
    of view that isn't noticed by most. This should matter to everyone,
    since for instance we all share the road.
     
    dumbstruck, Jul 29, 2005
    #15
  16. dumbstruck wrote:

    I am no iguana in being able to
    There is an optical illusion at work there due to the asian epicanthus,
    but sure, young people tend to have larger versional ranges. 45 degrees
    is close to the maximum possible.

    No, with that p.d., the pupil will be decentered 5 mm inward from the
    geometrical center of the lens, leaving 33 mm of lens temporally and 23
    mm nasally.
    No, using the same p.d. and bridge size, you have the pupil still
    decentered inward, but now by just 1 mm, leaving 25 mm outboard and 23
    mm inboard.

    and I'm guessing a typical lense is about 20 from
    The smallest frame I personally have is a 42 mm eye with a 24 bridge,
    and it actually gives me pretty close to 45 degrees temporally and
    nasally, or a total 90 degree field of view. My p.d. is 64.

    And with a wider PD, this angle shrinkage gets
    Not exponential, not even...
    Your logic and your calculations are flawed. Any placement of the
    lateral eywire beyond about 45 degrees from the primary position is
    wasteful, looks bad, and is harmful to peripheral vision without
    offering any offsetting advantage to central vision. The ideal frame
    size is one where the eye size plus the bridge size equals the distance
    P.D. plus 0 for very strong lenses, plus 2 mm for moderate power lenses,
    plus 4 mm for weak lenses. Larger frames than that should be reserved
    for sunglasses or for people with very wide heads.

    w.stacy, o.d.
     
    William Stacy, Jul 29, 2005
    #16
  17. Reece

    dumbstruck Guest

    And add to that the angle of clarity allowed by the cone distribution
    in the eyeball. One chart on the internet suggests you still have some
    semblence of cones at 10-15 degrees, which agrees with the experiment I
    described where 45+15=60 degrees seems the limit I can see effectively
    to the side. I can even take off my glasses and angle them for 70-80
    degrees with passibly sharp vision. Regardless of theoretical
    calculations, I experience and rely on around 60 degree sideview and
    find it hard to believe that is physically unusual.
    Not sure what you refer to, but maybe a happy result of the light being
    offset by hitting a flat plane of glass at an angle and bending as it
    enters then unbending as it leaves. Kind of like why people spearing
    fish at an angle have to aim at a different angle (angles rather than
    offset since no unbending). Well, that is nifty, but probably gets
    largely cancelled out by the thickness of the lense and frame rim.
    The whole reason of saying -ish- and similar caveats earlier is to
    underline I am not making a pedantic quantitative description. It was
    just my qualitative description was being misunderstood, so I loosely
    move towards more words, terminology, and numbers simply to jog us out
    of what may have been an original honest misunderstanding. I am
    certainly not basing myself on thin air calculations to then decide the
    sky is falling; I concretely experience my sky falling and
    qualitatively relate this to how others sky must be falling.
    My personal experience absolutely refutes this, and I can't believe I'm
    so unusual. Maybe your calculations don't account for the fact that
    usefully wide frames are canted outward in a sort of pigeon toed
    fashion. Somewhere packed away I have about the widest lenses I've
    ever seen - not high, but just about like wraparound sunglasses. The
    concavity was centered relatively close to the bridge where the lense
    was thin. The top and bottom of lenses got modestly thick, but the
    outward edges were absurdly thick - maybe unusable in the fashion you
    describe if they weren't canted outward.

    When I switched to pilot style glasses, which are extremely optimized
    for side and downward vision by today's standards, that was still a
    concrete loss to me. The opticion solved it by increasing the toe-out.
    This isn't some imaginary help since I use that last edge of the lense
    and feel the loss where it ends.

    Used to have to back out of a narrow garage where folks speeded by in
    both directions just a couple feet outside the door. I knew the
    extreme danger of this even before the adjacent stall experienced a
    violent collision (partly due to "fronting" out, which was gave worse
    cone of view to the slightly closer traffic from left). Solution was
    to turn around to let your lense cover beyond the 180 degree view; that
    is let the eyerim settle at a painful 200 or so degrees with the entire
    exit area clearly seen through the lense. So I am very used to using
    the bitter edge of the eyerim and regretting it's constraints.
     
    dumbstruck, Jul 29, 2005
    #17
  18. When you say "see effectively" do you mean clearly, with precision, or
    do you mean see anything useful, or what? As I demonstrated in previous
    posts, your area of precise vision is limited to about 5 degrees.

    To demonstrate again, while staring at the 'x' below, how many words can
    you make out. Should be none, unless you are cheating. Now remove your
    glasses and look back at the x. The amount of useful information your
    brain has is about the same with and without your glasses on, right?




    x





    Now while you are looking at that x, put your glasses on and off and
    notice your peripheral vision. Should be about 180 degrees unless you
    have serious eye disease, and the extreme periphery should be somewhat
    better WITHOUT the glasses than with them. This is because the lens
    edge is blocking part of your vision and the acuity in the periphery is
    not sensitive to blur. It IS sensitive to blocking by lens edge.

    The top and bottom of lenses got modestly thick, but the
    An obvious result of too large a frame. Just like I have said, over and
    over again. And now you have that thick wedge of lens blocking just as
    absurdly large a crescent of your peripheral vision! The defense rests!

    w.stacy, o.d.
     
    William Stacy, Jul 29, 2005
    #18
  19. Reece

    dumbstruck Guest

    I meant pretty darn good, but not perfect. By chance, I did that
    experiment in a blue room with blue reference points. Some casual
    reading suggested blue cones are much more widely spread out than the
    other color cones, so maybe more than 5 degrees works for blue.
    If I did it right I can see one word. That helps put me in the mood to
    review some concessions that probably slightly undercut my case:

    1) Each experiment suggests I may have a tiny edge in iguana or
    extra-enabled capabilities. I fought this conclusion all the way, but
    it could account for my sensitivity to constraints that aren't such an
    issue to others.
    2) My new frames must be grossly misfitted, because they are looser
    dimensions than the above, yet give such narrow view of field that I
    feel like one of those dogs wearing a plastic cone over it's head to
    prevent it from chewing itself. Don't understand it but probably the
    memory metal has it sticking too far out from my face. How embarrasing
    if that was the root of my problem.

    3) Think I was assuming too many others shared same narrow vision
    problem due to confusing irises with pupil openings. Was going to post
    some pictures of folks looking near the edge of their glasses at a
    fairly shallow angle, but now realize it was only their irises that
    appeared near the border whereas the little pupil had lots more room.

    4) That little zig zag that light takes intercepting even a planar
    lense sounds like a lucky benefit with no drawback, if I understand it
    correctly. There must be a name for that. There was some unhinged
    kook on this forum always claiming having to wear glasses is a
    blessing rather than a curse; maybe he should be taken more seriously
    <grin>.

    So I think I have a case, but it may be less urgent than I thought.
    But I still feel brimming with forsight re my comment that I use these
    narrow frames for expendable situations. Just hours ago some vagrant
    stole my glasses and other stuff while I went swimming. Hundreds of
    other times this would have been a painful loss, but now I'm almost
    sorry to have tracked down the guy and retrived the stuff from him...
     
    dumbstruck, Jul 30, 2005
    #19
  20. Reece

    dumbstruck Guest

    To demonstrate again, while staring at the 'x' below, how many words can
    Bet you thought seeing one was a guaranteed sign of cheating, but I
    think an old binocular issue is making more mischief. One eye at a
    time works ok; I see none, or more like 2 half words. Both eyes and
    probably a dominant one sees the same but a lazy eye picks up something
    elsewhere. Could explain a yearning to support wide angle vision if
    eyes can diverge Gene Wilder style.

    Eye doc diagnosed this after I made monthly visits with crazy
    prescription variations - lazy eye apparently can defocus under stress
    as well as mispoint. Now I can jump out of these rare skewed episodes
    by closing the good eye for a while. Must remember to do this if
    needed before any eye test...
     
    dumbstruck, Jul 30, 2005
    #20
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