PD's nuts!

August 10, 2008 6:44 PM

What is wrong with my nauseating (but clear) glasses which do not preserve shape throughout the field of vision?

I bought a new pair of glasses online, and love the savings and the looks, but am having trouble adjusting to the new prescription, I think. It is the first time with astigmatic correction, maybe, but there are couple other things that I was mulling over as the possible cause. The nauseating part is tracking an object as I turn my head--it distorts and skews differently depending on where it is in my field of vision (though it is pretty much always in focus). In particular, towards the top things shrink vertically, the top left skews ccw, the top right skews clockwise (it's tough to tell about the bottom).

My new optometrist "forgot" to write down the Pupillary Distance measurement on the prescription, and I was disgusted enough with their salesmanship that I ended up calling my old Lenscrafters to see what was used there (it was within the Net's typical range). But actually, I seem to remember the same thing happening with my last pair, though it that case it was free to have the lenses remade. They came out thicker (about as thick as now, actually), but non-distorting. They definitely remeasured my PD at that point, but may have adjusted the new glasses slightly in person.

I've now read about the "prism effect" which I assume to be produced by a wrong PD measurement. Since I'm tied to the online shop for half-price remakes, is it more likely that:
a) the lenses are somehow inferiorily made in their edge territories, and I should break down and buy local.
b) the PD is wrong, I should be assertive and get a PD measurement from the new doc [or, I should have them measured for accuracy there]
or
c) the new cylindrical measurement, though unblurifying, is distorting in a way that isn't true to my eye at large angles?

Or... something else?

posted by gensubuser to health & fitness (11 comments total)

perhaps
d) I've been nauseated by skewing glasses, and it will only take a few weeks before they will not cause you to crash your car.
posted by gensubuser at 6:50 PM on August 10, 2008

How long have you been wearing them? Are you alternating with your old glasses, or trying to wear just the new ones?

Option 1 is to give it a solid two weeks. You'll be used to them before then, even if the formula is actually wrong.

Option 2, if you really think they missed something regarding the PD, is to be assertive and get it fixed. You'll still have to do some adjusting when the correct lenses arrive.
posted by beagle at 7:43 PM on August 10, 2008

For the record, I think I had the same problem when buying glasses online. I theorized that the pupillary distance was the thing that did it, 'cause I didn't know mine either when it came time to buy, and instead measured it myself. But I'll definitely be interested to see what other answers we get here...
posted by limeonaire at 9:52 PM on August 10, 2008

I too just got my first pair of glasses with astigmatic correction, and it took a few days of adjustment before I stopped wanting to hurl all the time.
posted by crinklebat at 10:00 PM on August 10, 2008

I started wearing glasses for the first time ever last spring, so I only have that one point of reference on one pair of glasses. I don't have astigmatism, but there was a huge visual shift whenever I turned my head with my glasses on. I think it lasted about a week, and now I get nauseous when things don't skew when I'm not wearing my glasses.
posted by hwyengr at 1:00 AM on August 11, 2008

I have this problem every time I get new glasses, regardless of where I bought the glasses. It goes away after a few days, once your eyes (well, actually, the vision processing parts of your brain) adapt.
posted by randomstriker at 1:23 AM on August 11, 2008

One thing you might want to do is go to a glasses shop nearby and have them measure the lenses against your prescription to make sure that the lenses are actually correct. When I've gone to various Lenscrafters and Pearl Vision stores they've usually been pretty nice about checking over any pair, especially if they're not busy. I've been having lots of trouble with getting the right prescription and the right glasses over the past few months, so I really feel your pain. And nausea.

About Pupillary Distance: While it is important for it to be close, the actual measurement can vary by a few millimeters depending on who is measuring you and how.

Also from what I've found, people who have astigmatism in only one eye or much worse from one eye to the other tend to have a bit of shape distortion when adjusting to a new lens. I'm equally astigmatic in both eyes, so when shapes are off to me it has meant that there is another problem with the glasses.
posted by monopas at 4:06 AM on August 11, 2008

I bought two pairs of glasses online, and they were terrible. Instant headaches. I can't explain why, the technical details are correct. My guess is simply cheap lenses.
posted by gjc at 5:29 AM on August 11, 2008

Is this a Star Trek warp effect? Your description sounds like it. When I had this problem and took the glasses back to a Lenscrafters, I was told it was related to curvature of the lenses and of the particular material. (These were not for astigmatism, and they were LC's lightest weight lens. YMMV on the source of the problem - who knows if you can believe techs at every Lenscrafters...)
posted by whatzit at 5:38 AM on August 11, 2008

See also this thread from just two days ago.
posted by Tubes at 8:34 AM on August 11, 2008

The answer is c., especially since this is your first astigmatism correction. You'll get 100% used to it in a few days, but you will need to wear the glasses pretty much all the time.
posted by ikkyu2 at 8:39 PM on August 11, 2008