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Medical Forum / General / Vision / August 2006bad perscription and big frames
I just got a new pair of perscription sunglasses. I purchased the Ray Ban Wayfarers, which are a quite large plastic frame. I noticed when I put them on that everything was a little distorted, especially on the sides. I felt taller and had weird depth perception, almost a "fisheye" effect. Is this a natural thing to happen with a really bad perscription/astigmatism and large lenses? I can see find when I look straight, everything just looks a little off on the sides. It isn't such a big deal, but is there anyway to remedy this or should I just adjust to it? Thanks for everyones' help, Alex Dear Alex, You might be over-prescribed for astigmatism. Perhaps you could ask them to reduce the amount of astigmatism, consistent with passing the 20/20 to 20/30 line. Best, Otis > I just got a new pair of perscription sunglasses. I purchased the Ray > Ban Wayfarers, which are a quite large plastic frame. I noticed when I [quoted text clipped - 10 lines] > Thanks for everyones' help, > Alex I don't think that is it. I have glasses (smaller frame) with the same perscription and those feel fine. Regards, Alex > Dear Alex, > [quoted text clipped - 21 lines] > > Thanks for everyones' help, > > Alex >I don't think that is it. I have glasses (smaller frame) with the same > perscription and those feel fine. Then "bad perscription" might not be the best subject line. Larger lenses will seem to have more barrel distortion just because they have a larger diameter. Barrel distortion increases with distance off the eye, and thickness, and base curve, and index of refraction. Changing any of these will alter the barrel distortion you've learned to expect in the old glasses. Most of the time the new distortion becomes less noticeable in the first few wearings. If it doesn't, begin by adjusting the frame to try for a closer fit, before changing frames. -MT >I don't think that is it. I have glasses (smaller frame) with the same > perscription and those feel fine. [quoted text clipped - 25 lines] >> > Thanks for everyones' help, >> > Alex I think that's probably it Mike. Is it also possible that the optician "fit" the lens wrong. I remember she put a little machine up to my face and looked through it, I assume to take measurements. Could the focal point be off. I notice that when i hold the glasses higher on my face, so my eyes look through the bottom, I get less distortion. > >I don't think that is it. I have glasses (smaller frame) with the same > > perscription and those feel fine. [quoted text clipped - 47 lines] > >> > Thanks for everyones' help, > >> > Alex >I think that's probably it Mike. You're describing barrel distortion pretty well. Especially if your astigmatism is "against-the-rule." > Is it also possible that the optician "fit" the lens wrong. I remember > she put a little machine up to my face and looked through it, I assume > to take measurements. Could the focal point be off. She wasn't measuring focal point. She was measuring the distance between your eyes, so the lens centers could be placed horizontally in the frame. Normally, vertical measurements aren't done with single-vision lenses, because labs use the geometric center to determine placement up-and-down. > I notice that > when i hold the glasses higher on my face, so my eyes look through the > bottom, I get less distortion. Geometric distortions like barrel are different as you go further from the center. If the optical centers are placed too low, I'd complain. -MT >>I don't think that is it. I have glasses (smaller frame) with the same >> perscription and those feel fine. > >Then "bad perscription" might not be the best subject line. LOL.. I'm guessing some people in the states say it "perscription".. we see it often and it is so funny. Ann >Larger lenses will seem to have more barrel distortion just because they >have a larger diameter. [quoted text clipped - 42 lines] >>> > Thanks for everyones' help, >>> > Alex I think you mean "high" prescription, not "bad" which would indicate "wrong" Rx. Anyway, a large wrap around frame requires you to look at an angle different from the normal perpindicular angle, which changes your "effective" Rx. Some labs can correct for that (and some docs can too), but certainly not all are even aware of this problem. The Rx needs to be adjusted for the degree of "wrap", or you need to select a more "normal" frame. w.stacy, o.d. p.s. you may laugh at ol' otis' posts, but do not question them... >I just got a new pair of perscription sunglasses. I purchased the Ray >Ban Wayfarers, which are a quite large plastic frame. I noticed when I [quoted text clipped - 12 lines] > > Dear Alex, You have a lot on info to go on, but be sure that the base curve of the lenses, both old and new, are matched because it will affect the image that you percieve. Dr. Tom > I just got a new pair of perscription sunglasses. I purchased the Ray > Ban Wayfarers, which are a quite large plastic frame. I noticed when I [quoted text clipped - 10 lines] > Thanks for everyones' help, > Alex |
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