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Medical Forum / General / Vision / March 2006how much off for pd
I just got new glasses 2 weeks ago. The optician hand measured my PD at 62. Last week I found prescription sunglasses at another shop, there the optician used a marker on my glasses, measured the marks, and then followed up with some sort of machine that measured the PD as well. She found my PD to be 68. Would, could, should, this cause me problems? Is 6 mm off on PD a problem? Since then I have been getting 'tension headaches' in the afternoon/evenning. But to be honest, I cant quite decide if this started with the new glasses, or if my current stress and a little paranoia has set in:-) Without naming the shop, or knowing their policies, does anyone have any suggestions on a possible recourse? Thanks 6mm can be significant, and it may not. It depends on the script, whether large or small, plus or minus, whether you have excess convergence or divergence facility. Either of the two may have been wrong, go back to your optom and get it checked out. dr grant If you are a U.S. citizen, welcome to the "Wild Wild West" known as opticianry. There is no federal standard for optician qualifications, and in many states it is an unregulated industry. Here in Illinois, for example, your hair stylist is licensed, and the person who puts chemicals on your lawn is licensed...but your "optician" doesn't have to graduate from high school. During my 25 years of practicing optometry here in Illinois, I have had people walk in my front door with two left lenses in their glasses, bifocals that were placed upside-down and even lenses that were switched between a husband and wife. Grant is right...have your optometrist take your PD and find an optician you can trust. Thanks to both of you for your prompt reply. I will consult my optometrist. But in response to catman if I post my script could you comment further on the 'signifigance'? -3.00 +0.25 002 -3.00 +0.50 180 The second optician (the one who was thoruogh) told me that she had quit her previous job at a 'national' optical store because over the years that she worked there, the employed fewer and fewer licensed opticians, and more and more 'eye candy', or as she called them 'Brititany and Tiffinany'. Where she now worked, they only employed liscensed opticians. A lesson that I have now learned. Thanks. I thought the industry standard for PD is +/- 2mm for powers over 2D in any meridian and 1mm above 4.5D. As the power increases, the effect of mal-positioned optical centers increases. It also has to do with an individuals ocular alignment/positioning and their sensitivity to altering the convergence/divergence thresholds. Some folks find 1mm off to be uncomfortable and others might actually benefit from a 3mm error---if it's in "the right direction." Personally, I like to mark the horizontal and vertical centers for each eye separately and in the eyeglass frame to be used for the Rx. Less returns and unsatisfied patients that way, although it does take an extra minute or two to do that extra work. LB, O.D. >I thought the industry standard for PD is +/- 2mm for powers over 2D in >any meridian and 1mm above 4.5D. As the power increases, the effect of >mal-positioned optical centers increases. From Z80.1-2005 Single vision lenses Vertical Prism Imbalance Less than +/- 3.50D.......... .33^ total Over +/- 3.50D ..................1mm difference Horizontal Prism Imbalance Less than +/-3.00D....... .67^ total Over +/-3.00D................. 2.5mm total >It also has to do with an individuals ocular alignment/positioning and >their sensitivity to altering the convergence/divergence thresholds. [quoted text clipped - 5 lines] >returns and unsatisfied patients that way, although it does take an >extra minute or two to do that extra work. That's why the glasses from your practice feel more refined than the glasses from the other opticals. >LB, O.D. Regards, Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical ~~~~~~~~~~~~~~~~~~ "If a million people believe a foolish thing, it is still a foolish thing." - Anatole France Thanks to those who commented. I went this morning to the store where I got my glasses. I explained to the optician about my eye strain and the possibility of his missing my PD measurement. He checked again, this time by hand and by marking my glasses, and he came up with a PD of 67.5. He appologized for his mistake and ordered new lenes. A final note though. He is a liscensed optician. Again thanks for the advice. Another final note :-) I am quite surprised by the lack of stadardization in the industry. I have a quite large and round head and have a really tough time finding frames that do not press against my temple. I went to 6 different places usually without a suitable frame available. In the process I learned some about the numbers applied to the size of the frame. There is the bridge measurement, the eye measurement, and the number for the length of the arm of the frame. Excuse me if I got the vocabulary wrong. But there is no OD (outside diameter) available for the frames. What I mean is the actual distance from arm to arm across the frame. The measurement would be very helpful to me in quickly finding a frame. Thanks > In the process I learned some about the numbers applied to the size of > the frame. There is the bridge measurement, the eye measurement, and [quoted text clipped - 4 lines] > mean is the actual distance from arm to arm across the frame. The > measurement would be very helpful to me in quickly finding a frame. I think you've already named it. Double the "eye measurement" (eyesize) and add the "bridge measurement" (DBL, distance between lenses). -MT Mike, Double the eye measurement plus the bridge is actually not the whole story. The glasses that I have found to fit have an additional piece between the lens and the arms. I don't believe that that is accounted for in the above measurements. I think that you could find two frames with identical measurements, one frame with the arms attached directly to the lens (close to) and the other with arms attached as much as 10 mm out from the lens. If I'm correct about this, then clearly the OD of the frames would be different, I suppose the second frame would be Bridge+(2xEye measurement)+(2x10 mm)= OD Hopefully that made sense. And perhaps I'm not correct in this. Some frames were marked Big Man frames. The ones I did buy are 56 19, but like I said, they have an additional length to them outside of the lens. |
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