Cloudy polycarbonate, anyone?

**stargazer** · 10-12-2004, 10:29 AM

Just wondering if anyone else has noticed a recent problem with polycarbonate lenses being "coudy". We are finding a recent rise in the number of returns in which the polycarbonate (mostly SFSV), has turned cloudy after 6+ months in the field. We have found no common denominator in distributor or manufacturer. These lenses have NOT been AR coated. We have seen the problem on both front and back surfaces (although primarily back).

If anyone has had any experiences with a similar problem, or feels they can help troubleshoot, I would be happy to provide additional details.

TIA

**Jacqui** · 10-12-2004, 10:47 AM

Are these being backside coated?? I'm thinking maybe the coating is turning cloudy rather than the lens.

**ziggy** · 10-12-2004, 11:06 AM

are they the same manufacture? what about lot #'s ? could just be a bad batch,, I agree with Jacqui, it's the coating.

**stargazer** · 10-12-2004, 11:21 AM

Not always the same manufacturer and not always occuring on the back surface. The one thing that we found interesting when examining is a pattern similar to that of an electric burner which follows the symentry of the lens shape. We're wondering if it could be from the finishing process??

But . . . let's say it IS from the coating. Why would you think it would be starting to cloud after a significant amount of time??

Thanks again!

**Jim** · 10-12-2004, 12:54 PM

Beware of solvents like acetone (finger nail polish remover) and other products. Clean poly lenses with soap and water only.

**ziggy** · 10-12-2004, 01:27 PM

Jim brings up a good point, what about the gender of the patients? mostly female? If so it could be from some type of cleaning solvent. the pattern of the "crazing" sounds odd, does it go around, like a stove burnner?

**Chris Ryser** · 10-12-2004, 01:34 PM

Originally Posted by stargazer

But . . . let's say it IS from the coating. Why would you think it would be starting to cloud after a significant amount of time??

All poycarbonate lenses are coated on the plus as well as on the minus side.

It would be the coating that gets cloudy and milky. We encounter that same effect when using an AR stripper for CR39 on Polycarbonate lenses.

Acid, Acid fumes and or other chemical fumes in a workplace could be the culprit.
Another possibility could be a lens cleaner containing chemicals that are not compatible with the coating. Tell patients to use only lens cleaners that are made from surfactants (soap base) and not containing any solvents.

**stargazer** · 10-12-2004, 02:03 PM

Thanks for the conversation! I'm in "the lab", so I am aware of poly processing, and can only "advise" the cleaning recomendations to the ECP's.

I regret that I have not paid attention to gender, but certainly will from now on.

Yes, the pattern does go all the way around, exactly like a stove burner (although sometimes a squished one :) ) That's why we were wondering if it might be some type of stress (although we have never seen stress effects like this)

Thanks, again

**JRS** · 10-12-2004, 03:26 PM

If the "stove burner" look is about the size of a quarter (squished as you say) so it looks like it's oval, and it is centrally located, it could be crazing.

**Chris Ryser** · 10-13-2004, 03:46 AM

Originally Posted by JRS

If the "stove burner" look is about the size of a quarter (squished as you say) so it looks like it's oval, and it is centrally located, it could be crazing.

Crazing is only a result ......................not a cause

**Pete Hanlin** · 10-13-2004, 07:36 AM

Actually, the crazing that JRS mentions would appear to look like "cloudiness." As Chris infers, this is a symptom of lens flexure or heat stress (which has a number of causes- edging, lens sizing, exposure to heat either during dispensing or afterwards, etc.). Also, you may notice that- when the lenses are removed from the frame- some of the cloudiness appears to become less noticeable. If this is the case, it is almost certainly crazing.

You mention, however, that the lenses are not AR coated, and the crazing I usually see is on AR coated lenses.

If you would like to send some lenses in, I can have a look at them (and if I'm stumped, I can send them over to our R&D team for further analysis). I can also take a couple pictures and post them here for everyone's observation.

If you wish, just send some samples to:
Pete Hanlin
c/o Essilor of America
2400 118th Avenue North
St. Petersburg, FL 33716