 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Medical Forum / General / Vision / November 2005Prism correction
I've posted a few times on here about how I'm currently doing vision therapy. I'm having some sort of eye teaming/convergence problem, and the doc identified that my eyes relax slightly outward. I don't know all the correct terminology to use. I have a fairly mild Rx, almost all astigmatism in the 180ish axis (I hope I'm saying that right) around -1.00. When she first came up with my diagnosis, I asked when prism correction is appropriate, and she said that for me it wouldn't work. I didn't really understand the explanation, something like that my eyes would just adapt to the prism and I'd have the same problem over again. In going through this VT stuff though, one of the things I'm doing is looking at these tranaglyph things with red/green glasses. They basically seem to be making it so I need to go fairly well cross eyes to converge the red and green images, as though I were looking at something very close to my face. I suppose the red/green thing is important because it makes it really obvious if one eye gives up. Now to the point. I've noticed that after looking at some of these really close things for a few minutes my vision is much more blurry. It takes several minutes to get back to normal. Here's my theory: the fact that my eyes tend outward is physiological. I developed my astigmatism when I started doing a lot of close computer work (this is true), because I maintained this close convergence for long periods of time and it physically affected the shape of my eyeballs (pulling my eyes together far from their desired/relaxed state). Looking even closer with these 3D cards temporarily makes the astigmatism even worse. Is this reasonable? If this is the case, would it make sense to get some glasses with prism correction for close work to take some of the strain off? It seems that after some time of using them, I might be able to remove the astigmatism correction if my eyes can go back to their "pre close work" state. I'd much rather have glasses to wear while reading, and then not wear any for normal daily activities. Am I making this all up? TIA > It seems > that after some time of using them, I might be able to remove the [quoted text clipped - 3 lines] > > Am I making this all up? TIA Only the part about close work causing astigmatism. Would your ears grow more convoluted if you listen too close to the speakers? -MT > > and then not wear any for normal daily activities. > > [quoted text clipped - 4 lines] > > -MT Are you joking? I don't think it's at all unreasonable to consider that one's eyes could be affected by straining to cross them far away from their relaxed state. A better analogy might be, would your arms get longer if you started hanging lead weights from your hands all the time. I'm not saying I know my theory to be true, but it deserves more consideration, or a more reasoned explanation of why it is wrong. Plus, I came across a journal article indicating that symphony musicians tend to develop astigmatism in the axis corresponding to the way they cock their heads to read the music. I'll dig it up if you like. And if I'm wrong, I'd like to find out why my vision becomes blurry after my eyes are "crossed" for a few minutes during vision therapy. Thanks. > I don't think it's at all unreasonable to consider >that one's eyes could be affected by straining to cross them far away >from their relaxed state. Temporary muscle spasming, yes, structural change, no. > A better analogy might be, would your arms >get longer if you started hanging lead weights from your hands all the >time. > > Great analogy. They might feel like they're getting longer, but you'll never be an orangutan. >I'm not saying I know my theory to be true, but it deserves more >consideration, or a more reasoned explanation of why it is wrong. [quoted text clipped - 3 lines] >like. > Bogus idea, popular eons ago. My sis is a pro violinist and her astigmatism hasn't changed significantly since she was a little girl. >And if I'm wrong, I'd like to find out why my vision becomes blurry >after my eyes are "crossed" for a few minutes during vision therapy. > > Muscle tonus. Totally understandable and expected. w.stacy, o.d. > > I don't think it's at all unreasonable to consider > > that one's eyes could be affected by straining to cross them far > > away from their relaxed state. > > Temporary muscle spasming, yes, structural change, no. Here's a link to the article. Are you saying it's garbage? I contacted the author a while back and he still stands by it and is at least reaosnably well, if not highly, respected in the field as far as I can tell: http://www.babousa.org/Symphony.htm Besides, I simply find it very hard to believe that my eyes randomly got worse in the course of a year or two after starting ~8 hour per day computer work (after being 20/20 for 24 years). Anything's possible, it just seems unlikely and I'm not hearing any other explanations. Does anyone have data that correlates the number and severity of prescriptions with the amount of reading and close work a person does? I work in an environment where everyone reads and uses computers constantly, and 2/3 of us wear glasses. Maybe other people just don't care about blurry vision, I don't know. > > A better analogy might be, would your arms > > get longer if you started hanging lead weights from your hands all > > the time. > > > Great analogy. They might feel like they're getting longer, but > you'll never be an orangutan. Who knows. I bet if you stretched yourself on a rack 8 hours a day, you'd be a few inches taller after a year. I also think you'd settle back after a while if you stopped. > > And if I'm wrong, I'd like to find out why my vision becomes blurry > > after my eyes are "crossed" for a few minutes during vision therapy. > > > Muscle tonus. Totally understandable and expected. > w.stacy, o.d. I'm sorry, what does this mean? > Here's a link to the article. Are you saying it's garbage? I > contacted the author a while back and he still stands by it and is at > least reaosnably well, if not highly, respected in the field as far as > I can tell: > > http://www.babousa.org/Symphony.htm He may be a prolific writer, but I think he is pretty far out of the mainstream of thinking in the field, or at least he was when the article was written 18 years ago. > Besides, I simply find it very hard to believe that my eyes randomly > got worse in the course of a year or two after starting ~8 hour per day > computer work (after being 20/20 for 24 years). Anything's possible, > it just seems unlikely and I'm not hearing any other explanations. I don't disagree that extended computer use has precipitated an increase in myopia. I've obvserved it over the years. I think you were referring to short term stresses doing the same thing, which is what I challenged. > Does anyone have data that correlates the number and severity of > prescriptions with the amount of reading and close work a person does? > I work in an environment where everyone reads and uses computers > constantly, and 2/3 of us wear glasses. Maybe other people just don't > care about blurry vision, I don't know. There are loads of data on this. Everyone knows that myopia is largely an effect of excessive close environment of the post-industrial age. The devil is in our inability to prevent it. > Who knows. I bet if you stretched yourself on a rack 8 hours a day, > you'd be a few inches taller after a year. I also think you'd settle > back after a while if you stopped. No argument there. >>Muscle tonus. Totally understandable and expected. >>w.stacy, o.d. > > I'm sorry, what does this mean? Human skeletal muscle, when continuously stimulated, tends to retain a semi contracted state for a period after such stimulation. w.stacy, o.d. > I don't disagree that extended computer use has precipitated an > increase in myopia. I've obvserved it over the years. I think you > were referring to short term stresses doing the same thing, which is > what I challenged. You're the expert. It just seemed more than reasonable to me that perhaps straining to cross the eyes over the long term might actually pull on the eyeball in one dimension causing elongation and astigmatism. The anatomy of the eye would say whether this is even possible, and which dimension the astig would be in if it were possible. I'm a total lay person, so if you say the data and/or anatomy doesn't support this, I believe you. Is there data on the astigmatism impacts of extreme close work? I say "extreme" because my theory was that if I'm starting with eyes that want to tend more outward than normal, "normal" close work might affect my visual system in the same way as repairing watches (or whatever) would for the average person. It just seemed more than reasonable to me that > perhaps straining to cross the eyes over the long term might actually > pull on the eyeball in one dimension causing elongation and > astigmatism. If you look at the anatomy of the extraocular muscles, you'll find they exert primarily a tangential pull on the eye, which causes it to turn, not to elongate. The anatomy of the eye would say whether this is even > possible, and which dimension the astig would be in if it were > possible. I'm a total lay person, so if you say the data and/or > anatomy doesn't support this, I believe you. The anatomy speaks for itself. That is not to say that what you are suggesting is "impossible", and I do believe that small forces over long periods of time can and do influence the shape of the eye. > Is there data on the astigmatism impacts of extreme close work? I say > "extreme" because my theory was that if I'm starting with eyes that > want to tend more outward than normal, "normal" close work might affect > my visual system in the same way as repairing watches (or whatever) > would for the average person. In over 30 years of practice and monitoring thousands of eyes developing over time, I've seen little change in most peoples' astigmatism. I've seen large changes in myopia, but relatively little in astigmatism (except for eyes that are injured or diseased, or those that have been subjected to long term contact lens wear). w.stacy, o.d. > > > Muscle tonus. Totally understandable and expected. > > > w.stacy, o.d. [quoted text clipped - 3 lines] > Human skeletal muscle, when continuously stimulated, tends to retain > a semi contracted state for a period after such stimulation. Help me to understand. The muscles you are considering here are the ones that "point" the eyes, right? These are the ones under stress while I'm converging them for the tranaglyph. If those muscles were having trouble, how would that make my vision blurry? Isn't that determined by different muscles, the ones that do the actual focusing? > while I'm converging them for the tranaglyph. If those muscles were > having trouble, how would that make my vision blurry? Isn't that > determined by different muscles, the ones that do the actual focusing? You're right about that.. the outside (pointing) muscles are hugely different from the ring-shaped inside muscles that you use to focus. But they are hardwired together so that you can't converge without accommodating, and vice versa. You use the same effort to produce both effects, in a predictable ratio. -MT > I'm not saying I know my theory to be true, but it deserves more > consideration, or a more reasoned explanation of why it is wrong. Normally astigmatism changes very slowly. On average it increases gradually throughout life, though it does accellerate for some and may dramatically decline for others. The axis (orientation) of astigmatism in each eye is almost always symmetrical left-and-right. This might support your argument. But when it does change, it tends to increase or decrease along the same axis it has from birth through adulthood - axis numbers seldom cross the 90/180 meridians from year to year. More importantly, the same muscle forces that produce astigmatism oriented vertically couldn't likely create horizontal astigmatism in others. Not without major anatomical differences which don't exist. Astigmatism varies among ethnic groups - among 2500 kids in US schools, Hispanics were found to have about twice the prevalence compared to African Americans. Asians were similar to Hispanics, and whites somewhere in the middle. > Plus, I came across a journal article indicating that symphony > musicians tend to develop astigmatism in the axis corresponding to the > way they cock their heads to read the music. I'll dig it up if you > like. Tuba players don't start at age 2. In fact tuba players don't usually start with tuba. Even if the study used good methods, I'm inclined to think it's a statistical fluke, fun to read but the implications are largely out-of-touch with what really happens. > And if I'm wrong, I'd like to find out why my vision becomes blurry > after my eyes are "crossed" for a few minutes during vision therapy. There are really only two mechanisms. One is called "lens lock" where the crystalline lens deforms enough that it can take a minute or two to relax completely. The other is "spasm of accommodation", artificial accommodation "trained" by sustained effort. Sustained vergence effort would be enough to stimulate either or both of these effects. -MT > > And if I'm wrong, I'd like to find out why my vision becomes blurry > > after my eyes are "crossed" for a few minutes during vision therapy. [quoted text clipped - 11 lines] > > -MT Thanks for the reply. I may not be understanding what you are saying, but the thing I don't understand is that when I'm doing this VT stuff, my eyes, individually, are focussing at normal reading distance. The thing that's different is that they are much more than normally "crossed". When The exercise is done, things are blurry at that same distance. So it appears related to the strain of the eyes crossing, not the fact that the eyes have been focussed at a certain distance for a long time. I'm still fairly young; my eyes go between close and distance quickly. And the VT exercise is only for a few minutes anyway, nothing like reading a book for hours and then trying to look far away (which I don't really have trouble with anyway). > from their relaxed state. A better analogy might be, would your arms > get longer if you started hanging lead weights from your hands all the > time. I'm retired now. I recommend it highly, although the pay isn't great. :-) I try to walk three hours a day. I often do more. This is very good for my health. Of course, I have to realize that all this walking is going to shorten my legs. Isn't it? Wait a minute! Doesn't exercise make things *bigger*? Shouldn't my legs actually get longer because of my walking? I am anxiously waiting all of your expert opinions about whether my legs are going to get shorter or longer because of all my walking. After all, should I stock up on longer or shorter pants? :-)  SignatureDan Abel dabel@sonic.net Petaluma, California, USA > > from their relaxed state. A better analogy might be, would your > > arms get longer if you started hanging lead weights from your hands [quoted text clipped - 16 lines] > > :-) Wow, I'm pretty disappointed in this group. Is it really inconceivable to the point of absurdity that if you use your eyes in ways that strain and pull them that they might change shape slightly? As I said, it may not actually be true, but you need to either do better than this or just keep quiet about it. What do you expect from a usenet group? Everyone to listen to your arguement and agree?? There is plenty of research showing astigmatism developing according to the direction of eye movement, but it relates more to the lid pressure than anything else, not eye muscles. Secondly, the problem you have is convergence insufficiency, not exophoria. In CI, you ability to converge is impaired. The vision therapy you are doing is to train your system to be able to converge with ease. Prism correction will not achieve anything as the underlying issue is an inhibitory centre in your brain and this inhibitory pathway must be overridden in order to get you working comfortably for close work. grant > What do you expect from a usenet group? Everyone to listen to your > arguement and agree?? Absolutely not. I just hoped that I would not be mocked when I feel that my "theory" is at least conceivable. An explanation of why I'm wrong (for example, is the anatomy of the eye such that straining to cross the eyes could temporarily flex the eyes and change their shape, or not?), or a statement that research has proved otherwise, would suffice. Better yet, a plausible explanation (besides pure randomness) of the symptoms I'm seeing, like my vision getting worse when I started doing more close work, would be great. > There is plenty of research showing astigmatism developing according > to the direction of eye movement, but it relates more to the lid > pressure than anything else, not eye muscles. Okay. Interesting how previous replies would indicate that I'm a moron for even considering that how the eyes are used could affect astigmatism at all. Something about peoples' ears not changing shape from listening too hard. > Secondly, the problem you have is convergence insufficiency, not > exophoria. In CI, you ability to converge is impaired. The vision Help me understand the difference. I think the diagnosis was made based on my explanation of symptoms and the movement of each of my eyes when covered. Possibly also based on my verbal indication of when it became difficult for me to maintain convergence/divergence with prism lenses (I'm assuming, she didn't tell me what was actually happening all the time). How are the symptoms different between brain related convergence problems and physiological issues (exophoria?). > therapy you are doing is to train your system to be able to converge > with ease. Prism correction will not achieve anything as the > underlying issue is an inhibitory centre in your brain and this > inhibitory pathway must be overridden in order to get you working > comfortably for close work. If the natural resting state of my eyes is slightly outward, is prism appropriate? If not, when is it? > > I try to walk three hours a day. I often do more. This is very good > > for my health. Of course, I have to realize that all this walking is [quoted text clipped - 14 lines] > not actually be true, but you need to either do better than this or > just keep quiet about it. I was just trying to make a point, that just because something *seems* like it ought to work a certain way, that doesn't mean that it actually works that way. SignatureDan Abel dabel@sonic.net Petaluma, California, USA |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.