Lens Stress in Polarized Lenses???

**jeffsoptical** · 10-23-2008, 07:54 AM

I have a customer who is complaining about seeing blotches in her Polarized Progressive lenses in her wrap zyl bolle frame. I can see what she is talking about when she showed me outside in the bright sunlight by holding them up to the sky. I'm sure it's lens stress caused by the wrap zyl frame. I edged and mounted the lenses and they fit very well without being overly snug in the frame. I took the lenses and heated them in 200 degree water and then checked out the lenses and it did take away the stress blotches when not mounted in the frame, but when I remounted them I can see a few blotches in the corners. You can't see them unless you look at them in bright light or a polariscope. Is this customer being overly picky? What can I do?

Thanks

**LilKim** · 10-23-2008, 08:18 AM

What kind of material are they?

**jeffsoptical** · 10-23-2008, 08:20 AM

Cr-39

**chip anderson** · 10-23-2008, 09:21 AM

Don't think I have ever seen a large polarized lens without stress.

Chip

**LilKim** · 10-23-2008, 09:40 AM

I agree. It's just the nature of the lens and the wrap frame they're mounted in. Even unedged and unmounted, polarized lenses will show stress.

**OpticianVlad** · 10-23-2008, 10:47 AM

If the lenses are too tight in the frame it will make it worse.
Maybe it's not the size but the shape and frame curve. Some edgers elongate the shape of the lens.
In other words it cut a larger A measurement and that may cause a wrap frame to have extra stress on the lens.

**LilKim** · 10-23-2008, 11:15 AM

Some tracers do that as well. We have some issues with our 4T giving us a "squished" shape on some of those more rectangular frames. To compensate, we gently push in on the temples to lengthen the B meas. by a hair, and the lenses tend to fit much better with less stress at the corners and eyewire barrel.

**jeffsoptical** · 10-23-2008, 11:39 AM

I've had issues with some wrap frames where the A measurement was to large and the lenses wanting to pop out at the top of the frame and sometimes I just have to hand bevel the lenses to solve this problem.

These lenses fit very well and are not too snug on the 180 axis because there is no tendency for the lenses to want to pop out at all at the top of the frame.

The customer noticed the blotches using her computer outside. She's a realtor.

**MarcE** · 10-23-2008, 07:36 PM

I'm not sure you can fix this completely but you might be able to make it better. Try this.

Cut back the bevel by hand to make it steep. Many times zyl frames, especially the suns have very deep bevels. So the lens has too much stress because it is not fully seated into the frame. Then do a little hand edging to reduce the specific stress points.

I would also try to heat the frame just as hot as it will take without destroying it and then insert the lenses. This will allow the lens to reshape the frame upon cooling and distribute the stress over the entire circumference.

Harry C (if he can stop breaking and entering long enough to chime in) and Barry may have some better comments.

BTW, my new edger has a "Base 8" function that greatly reduces this type stress over my older one.

**jherman** · 10-23-2008, 09:50 PM

pressure is the cause,(as far as I can see) of the anomaly.

Originally Posted by MarcE

I'm not sure you can fix this completely but you might be able to make it better. Try this.

Cut back the bevel by hand to make it steep. Many times zyl frames, especially the suns have very deep bevels. So the lens has too much stress because it is not fully seated into the frame. Then do a little hand edging to reduce the specific stress points.

I would also try to heat the frame just as hot as it will take without destroying it and then insert the lenses. This will allow the lens to reshape the frame upon cooling and distribute the stress over the entire circumference.

Harry C (if he can stop breaking and entering long enough to chime in) and Barry may have some better comments.

BTW, my new edger has a "Base 8" function that greatly reduces this type stress over my older one.

**scriptfiller** · 10-24-2008, 08:25 AM

I have an Optronics 6E and set the bevel to fixed @ 1.10mm from the front. This does two things, it eliminates "ring-around-the-polarized" and distributes the bevel stress equally between the front and rear "sandwich" elements. Then if the RX will not fit within the eyewire/rim I will hand cut a V bevel and the lense fits just as good as the demo. Also, use the correct base curve, this is VERY key, it will eliminate lense flexure and also eliminate or reduce frame deformation.

I hope this helps.

**evville** · 10-27-2008, 07:06 PM

We have problems with groove jobs coming out elongated the small B .These jobs can be alot of problems we used 4 different types of tracers .The optronics 4 T , santinelli ,and now a Hoya tracer .I found all of them have different problems .Has anybody tried the A.I.T scan tracer?