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Medical Forum / General / Vision / July 2005Height 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. 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. > 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! 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. > 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 [quoted text clipped - 3 lines] > 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 [quoted text clipped - 5 lines] > 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. > 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. > 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. > I think it is a step forward to reduce the excessive > heights, although this is frequently overdone. But the [quoted text clipped - 4 lines] > 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 >But wide frames aren't going to fit inside the crash >helmet you should be wearing when you go outside >right? > > I was about to suggest contact lenses, but your most astute observation trumped me completely... w.stacy, o.d. > But wide frames aren't going to fit inside the crash > helmet you should be wearing when you go outside > right? 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>. so my > axe to grind is these narrow glasses that put pedestrians (and sport > players, etc?) at such a disadvantage. As has been pointed out to you, smaller is better as far as extreme peripheral goes. Having thought a bit about your argument about moving your eyes toward the moving object in your periphery so you can see it more clearly WITHOUT MOVING YOUR HEAD, I experimented a bit with my big glasses and my small ones. Guess what I found. I cannot force my eyes far enough to fixate on the temporal rim of even my smallest pair. Unless you have superhuman versional abilities, you can't either, so your argument evaporates into thin air. Small frames are BETTER then big ones! w.stacy, o.d. > As has been pointed out to you, smaller is better as far as extreme > peripheral goes. Having thought a bit about your argument about moving [quoted text clipped - 7 lines] > > Small frames are BETTER then big ones! 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... > 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! 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. > 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 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 > 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 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. 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 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. > Let's go thru some numbers. Earlier you said > [quoted text clipped - 7 lines] > either side puts a pupil in the center of a 56 wide lense; not bad with > 28 left over either side. 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. > But shrinking the lense width to 48 gives just 20 left outboard of the > pupils in the lense, 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 > center of eyeball sphere which gives a tightening 45 degree field of > clear view. 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 > exponential-ish-ly pathological. Not exponential, not even... > 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. 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. > 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. 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. > 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. 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. > And with a wider PD, this angle shrinkage gets > > exponential-ish-ly pathological. > > Not exponential, not even... 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. > Your logic and your calculations are flawed. Any placement of the > lateral eywire beyond about 45 degrees from the primary position is [quoted text clipped - 4 lines] > plus 4 mm for weak lenses. Larger frames than that should be reserved > for sunglasses or for people with very wide heads. 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. >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. 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 > outward edges were absurdly thick - 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. > 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. 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. > 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 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. > 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. 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... > > 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 > > If I did it right I can see one word. That helps put me in the mood to 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... > 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. I came close in an earlier post to asking you if you were exotropic. The thought did cross my mind, and that would explain our differences there. > 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... OK so I can conced to you that exotropes may need somewhat larger frames to accommodate their anatomical "advantage". w.stacy, o.d. 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. Definitely a problem. I hate those memory metal frames for that reason. If they don't fit right out of the box, they may never fit. Their memory seems to be forever. I hadn't thought that that was the issue, but it may be the main one for you if the frame ends up splaying concave forward. Makes everything worse. sounds like this thread is finally unravelling. it's been fun. >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 [quoted text clipped - 5 lines] >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 [quoted text clipped - 10 lines] > > Reece >I went from a taller pair of glasses lenses to a more stylish shorter pair >of lenses about a year ago. Short lenses >cause unnatural forcing of the head down, All manner of things affect your posture: your (possibly crummy) computer chair; your decision to pimp out in your ride and tip the seat as far bas as it will possibly go while still allowing you to see through the steering wheel and over the dashboard. Your shoes affect your posture, so do your clothing choices and your food choices. When I wore contacts I watched where I put my feet, having learned as a young child that my toys could break my toes. That's a hard lesson when you're 7 years old with summer just coming on... +++++++++++++ Reply to the list as I do not publish an email address to USENET. This practice has cut my spam by more than 95%. Of course, I did have to abandon a perfectly good email account... Update: I just changed glasses for the first time in a year yesterday after I made my previous post and it has made a huge difference. Not having to point my head down to see the 40% that was lost for a year is incredibly freeing. I feel like I just got over an illness. In my Kung Fu class yesterday my basic stance was so much more comfortable because my head was in a natural position and I didn't have to point my head down to see things, like a punch coming in during drills. And just getting something out of the refrigerator now means just tilting my eyes down rather than pointing my head down. What a burden wearing those more stylish glasses were, but I didn't realize it until recently. I will still wear the stylish ones for public presentations until I get a more stylish larger pair or go to contacts. Reece >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 [quoted text clipped - 20 lines] > > Reece
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