Cracking poly...

**AutumN** · 05-15-2007, 12:48 PM

I have a patient that came back after 7 mos with cracked lenses. Looks like stress fractures, so we re-did them, no problem. (that was in Jan.) Made sure that the new lenses were not tight in any way. She's just called saying they are cracking again. Now, I haven't seen them, so I don't know for sure if it's fractures, but the only other thing that I know of that tends to crack poly is a chemical reaction...windex, acetone etc. Does anybody know what else may cause this. Also, is there any way to tell if the lenses have been exposed to a chemical--outside of pixie dust?

A couple of years ago, I had a patient who came back with 2 pairs that kept cracking. She was emphatic she didn't use anything "bad" to clean them with, even gave her cleaner on 2 different occasions!! Finally after remaking both pairs like 3 times she admitted that she only used windex! I don't want to relive that fiasco.

**gemstone** · 05-15-2007, 12:50 PM

Is anyone putting loc tight on the screws?

**FullCircle** · 05-15-2007, 01:10 PM

Are they 1.0mm finish lenses that are especially flat? Do they have AR? Is the frame as flat as the lenses or is the frame slightly more curved?

**Chris Ryser** · 05-15-2007, 01:43 PM

Originally Posted by AutumN

Finally after remaking both pairs like 3 times she admitted that she only used windex! I don't want to relive that fiasco.

Unprotected (as hard coat) poly will start to craze when coming into contact with a lot of solvents. Windex contains methanol and will start a reaction.

Originally Posted by gemstone

Is anyone putting loc tight on the screws ?

Never seen poly in contact with lock tight...............what is the reaction ?

**mike.elmes** · 05-15-2007, 01:47 PM

I had this problem a lot. Micro fractures around drill holes......problem solved don't use poly on drill jobs....use either Trivex or 1.6 index mr8 material.
There is a solution you can apply to freshly drilled holes on Poly Lenses..... Drill Seal sold by Opto Chemicals.It works well. Also if locktite is applied to poly it can cause the micro fractures. I use locktite 222 ms threadlocker. It's suppose to be ok with poly.

**For-Life** · 05-15-2007, 01:57 PM

Rimlon or Rimless?

**AutumN** · 05-15-2007, 03:17 PM

This is a full frame, no AR, haven't used loc tight, and not 1.0mm. Don't know about the curve relationship of lenses to frame. (the other Optician's been working with her).

**For-Life** · 05-15-2007, 03:21 PM

Interesting. Are the edges polished?

**gemstone** · 05-15-2007, 03:31 PM

It could be something she is cleaning them with. She will probly never tell ypu.

**walleye** · 05-15-2007, 03:37 PM

We had this problem with a patient a year or so ago. Went through 3 pairs of poly lenses with cracks starting at the edge and moving toward the center of the lens. Full frame about a -6.00 not too tight and she insisted she only used water to clean lenes. I finally told the patient it was poltergeist-and in frustration had another lab redo them and no problem.

**gemstone** · 05-15-2007, 04:17 PM

Originally Posted by walleye

We had this problem with a patient a year or so ago. Went through 3 pairs of poly lenses with cracks starting at the edge and moving toward the center of the lens. Full frame about a -6.00 not too tight and she insisted she only used water to clean lenes. I finally told the patient it was poltergeist-and in frustration had another lab redo them and no problem.

Someone put loc tight on the screws. Probly your old lab.

**jherman** · 05-15-2007, 04:17 PM

speed and or sharpness?

**AutumN** · 05-15-2007, 05:47 PM

No polished edges either.

**For-Life** · 05-15-2007, 05:53 PM

Originally Posted by AutumN

No polished edges either.

oh there you go. That is your problem. Poly MUST be polished. You cut it dry and then polish it wet. If you do not polish then there are thousands of mini cracks on the side which can expand

**CME4SPECS** · 05-15-2007, 05:59 PM

Originally Posted by For-Life

oh there you go. That is your problem. Poly MUST be polished. You cut it dry and then polish it wet. If you do not polish then there are thousands of mini cracks on the side which can expand

I don't think so. I've been doing poly safety glasses for years, hundreds a year and never ever polish edges and no cracking.

**AutumN** · 05-15-2007, 06:01 PM

Really! I've never been told that, even by any lab I've dealt with. I only polish if the patient wants.

**For-Life** · 05-15-2007, 06:03 PM

Originally Posted by CME4SPECS

I don't think so. I've been doing poly safety glasses for years, hundreds a year and never ever polish edges and no cracking.

I have had it cracked. Sometimes depends on the coatings. It is the same reason why drill mounts crack.

**CME4SPECS** · 05-15-2007, 06:06 PM

Autumn are they sv or pal?

**AutumN** · 05-15-2007, 06:08 PM

I believe a PAL

**CME4SPECS** · 05-15-2007, 06:09 PM

what do you remove the markings with?

**CME4SPECS** · 05-15-2007, 06:23 PM

I'll this share this with you: I used some of BPI's mark-off (or whatever they call it) on a pair of poly pals. I smeared it on the markings and had a customer come in and i set the glasses down and waited on customer. When I finished I sprayed the lenses with cleaner and got them all cleaned. I did notice that the mark-off had oozed in the metal eyewire. Anyway I called the customer to let them know that their glasses was ready. He came in the next day , I was getting the glasses out of the tray and notice that the lenses were both cracked...right were the mark-off had oozed into the eyewire. So make sure that stuff isn't the culprit!

**AutumN** · 05-15-2007, 09:03 PM

We were using solves-it for poly and it also cracked some lenses, but that usually happened before I was done cleaning them off. I also had it happen with another mark remover in a pen type deal that was supposed to be ok for poly, but cracked the first 2 pr I tried it on. Now we use a remover that we got from our lab (can't remember the name at the moment) and we haven't had any problems. We've been using it for about 3-4 months now. I just think if it was from my mark remover oozing in the eyewire, it would have showed up much sooner than 5-6 months later. I'm thinking maybe it's something the patient is using for cleaning.