Polarization and headaches

[For-Life]

So I had a girl in a few weeks ago who had some expensive brand name sunglasses with a gouge in the lens. She wanted to save them, so she asked if we can replace the lens.

So I found in a catalog a polarized, brown, 8 base, backside AR coated lens. Her old lenses were just a regular brown, 8 base lens. Of course both are plano. So I figured I was really doing her a favour and she was excited. She got them and with the backside AR could notice the difference immediately.

She came back in today and told me that now she get major headaches and eye strain. She also mentioned that the frame is pinching behind her ears. So I figured that when I edged the new lenses there was some alterations in the fit. I re-adjusted them, hoping it would fix the stain and the headache.



So here is my question, if it is not the fit could it be the lens or even the polarization?

[chip anderson]

If the lens isn't wavy it's probably the pinching behind the ears. Can definitely do this, especially when worn for any length of time as on a road trip.

[remuspwr]

Maybe one of the lenses is off its polarization axis. 90 degs. off axis can give an almost 3D feeling to the lenses, thus leading to some eyestrains.

[For-Life]

Maybe one of the lenses is off its polarization axis. 90 degs. off axis can give an almost 3D feeling to the lenses, thus leading to some eyestrains.

I double checked that. Plus it shows up when I go to block it.


Chip I hope you are right.

[CEO]

The tolerance for off axis is very small, just 3 degrees for each lens. Some lens manufactuers keep very close tolerances, others do not. Also, the off axis could be compounded in subsequent processing. So, might want to look a little closer at axis to make sure it is within 3 degrees tolerance. Write me an e-mail at drips@youngeroptics.com and I could send you a little polarized checker for this.

Of course check for waves, off Rx, even base curve shock between having a clear lens in one base curve and sunwear in another, especially 8 Base can cause problems. Also, what is material, some people can get irritated from poly in polarized, due to polarizing material highlighting some of the stresses in poly. Also, if frame is highly wrapped, sometimes Rx needs to be adjusted to compesate for this, also grinding in prism. There are programs out there that can help you do this. If fact, some of these programs are downloadable from optiboard I think.

THeres lots of reasons, but axis is the most obvious.

[Lady Nicole]

I'm embarrased to say that polarization axis is someting I've never known to check, although it makes perfect sense :idea:

CEO, can you go into more detail on checking the axis with the "polarized checker" you mentioned?

[loncoa]

I have, over the years, had a small percentage of people who are uncomfortable in polarized lenses of any kind, and after checking all of the above and then some, have had to take them out of polarized. Which immediately solved the problem. I suspect there is some sort of spatial perception issue with polarized for these people. Some of them have had the symptoms you described. If you cannot find anything wrong with these you will just have to bite the bullet and redo them into conventional sunglass lenses, I guess.

[Jim Stone]

I have, over the years, had a small percentage of people who are uncomfortable in polarized lenses of any kind, and after checking all of the above and then some, have had to take them out of polarized. Which immediately solved the problem. I suspect there is some sort of spatial perception issue with polarized for these people. Some of them have had the symptoms you described. If you cannot find anything wrong with these you will just have to bite the bullet and redo them into conventional sunglass lenses, I guess.

The polarization has nothing to do with this problem.

[For-Life]

The polarization has nothing to do with this problem.

Well then?

[Jim Stone]

Well then?

That's correct. You probably fixed it when you adjusted them.

[For-Life]

That's correct. You probably fixed it when you adjusted them.

ah okay.

[Jim Stone]

That's correct. You probably fixed it when you adjusted them.

You already said she'd been wearing polorized lenses. I just hate Iocona has lost all these ,over the years polorized customers. Too bad. :finger:

[drk]

It's not out of the realm of possibility that some people react strangely to strange lenses. It's undoubtedly rare, though.

I do know this: wrapping a lens, even a plano lens, about 15 degrees will induce about 1/2 pd BI, causing the eyes to need to diverge. This is lens thickness dependent, I do believe, not directly power dependent.

Some folks could react to a little BI prism, for sure. Grind in about 1/2 D BO if it's a wrap, or take out a little faceform in these cases.

In this case, you don't have this variable, since the frame is constant.