Are these horrors caused by a wrong PD value and/or index?

Getting the best value for your money when it comes to eyeglasses, sunglasses, eye exams, and contact lenses.

Postby JamesM33 » Wed Feb 18, 2015 8:34 pm

I ordered glasses from a website that said to enter a PD value of 63 if it was not on our prescription. Not knowing what PD means, I just did what they said.

I get the glasses and something isn't right even though it's the same prescription as my current glasses. Lens strength seemed correct, but I had something I can only describe as focusing issues that made me want to puke. My research leads me to it maybe being a wrong PD value. I read that accuracy is more important as the lens strength increases (and my sphere is 5.25 and 5.50). So I go get measured and it's nearly a 68..... a 5mm difference from the "default" value they said to put in.

Contact support, send glasses back and they issue store credit.

Now I'm afraid to re-order.

Another thing is if I looked near the corner of the lenses, things appeared bent and shapes shifted as I walked. I understand this is normal to a certain extent, but this was really bad. Could the PD value have caused that or do 1.61 index lenses at my strength do that? At checkout they force you to get 1.61 at my strength, but I'm wondering if I should request 1.50 if that is the cause of the severe edge distortion..... or maybe that too was the wrong PD. What do you guys think?

I'm hoping all of this works out in the end. Save big money.
JamesM33
 
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Postby george » Thu Feb 19, 2015 10:33 pm

JamesM33,

I'm not an optometrist, but I Google really well :)

Here's my source on prismatic effects of wrong pupil distance

A pupil distance being off by 5mm seems pretty significant to me and you are correct that it has an even bigger impact when you have a stronger prescription (as you do). When the pupil distance is off, you are not looking through the center of the lens and that creates something called "prismatic" effects. Basically a prism bends light and when your vision is not going through the center of the lens, the light is bent. When the pupil distance of the glasses is smaller than the pupil distance of your eyes, and you have a plus lens correction, the light will be bent such that objects will appear farther away than they actually are (if I read the article referenced correctly). I think it also says that horizontal lines will appear curved. So - basically - it sounds like your issues are very likely due to do the wrong pupil distance.

I would give it a shot seeing if ordering with the proper pupil distance fixes your problem. Please let us know the outcome!
george
 
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