Height of glasses lenses affects head position

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

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 wrote:
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).

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.

>
> 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.

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.

"Reece" <(E-Mail Removed)> wrote in message
news:CPbDe.997$(E-Mail Removed). ..
>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.

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

>
> 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
>
>

> 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.

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.

> 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.

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 wrote:
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.

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
> 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.

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.

>
> 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!

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 wrote:
> dumbstruck wrote:
> 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.
>
> 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.

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.

> 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.

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.

> > 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!
>
> 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

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).

> 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%.

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 wrote:


> 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.

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 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

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.

> 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

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'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.

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 wrote:
> William Stacy wrote:
>
> 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.

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

-Quick