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Unread 02-08-2011, 11:23 PM
 
Location: Northeast Tennessee
6,870 posts, read 12,564,086 times
Reputation: 5077
Default "Cracking" lens in eye glasses!

Not sure what forum this should go in (please move to proper forum if this is wrong), but since it deals with the eyes, thought I would try here. About 2 years ago, I purchased some new glasses at a "value" eye glasses shop (even though I paid $300 for them!)... about 6 months ago the lenses started getting little cracks coming inward from the outer edges.... they were apparently out of warranty, because they would do nothing about it.

So... our work finally started offering eye insurance, so I went for a new exam and thought it was a good time to buy new glasses. I went to Lenscrafters this time (about a month ago), because last time I purchased glasses there, they lasted me 10 years. Well, tonight I noticed that these have started cracking the same way!

I am very gentle with my glasses and I mean very gentle. I wash them in cool water with a mild soap (they said was OK) (the water temperature I am using on them is not cold, not hot, but a cool-warm water around 65-70), so I know I am not overheating them causing this I dont think?? I have to wash them because I have greasy skin and thats all that I feel comfortable with getting them clean every morning.

I think these past two pair of glasses I have purchased that have done the cracking have polycarbonate lenses, which according to what I have researched online is supposed to be the best, toughest, etc, but thats not been the case with me.

I plan on taking them back this week to see what they intend to do about it.

Has anyone else had this issue? I am at a crossroads over it.

Thanks.
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Unread 02-09-2011, 11:14 AM
 
Location: Victoria TX
37,603 posts, read 31,193,090 times
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I recently discovered a crack in a lens, about 3/8 inch long, in the center of the lens. The lens is about 8 years old. It doesn't seem to be growing. I've been wearing glasses for 60 years, and I had never seen that before. So I strongly suspect that is some new characteristic of modern lenses, and probably now something to be expected.
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Unread 02-09-2011, 05:58 PM
 
Location: Northeast Tennessee
6,870 posts, read 12,564,086 times
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Thanks... yes, these are those "poly" lenses... the first of these I have had. My last ones were plastic and never an issue, but these past two pair are those poly lenses... maybe its something in the dish liquid causing it?
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Unread 02-09-2011, 08:15 PM
 
Location: Between Seattle and Portland
1,267 posts, read 1,383,985 times
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TS, I'm just about to send my first order in to a well-reviewed online vendor for eyeglasses and I did specify polycarbonate lenses for my progressive bifocal prescription. (The total cost will be just under $60.) Your experience caused me to do a little research, and I found this:

Clear polycarbonate is used to make eyeglasses because of its excellent transparency, durability, and high refractive index. This means that it bends light to a far greater degree than glass or other plastics of equal thickness. Since prescription lenses bend light to correct vision, polycarbonate lenses can be far thinner than glass or conventional plastic, making polycarbonate the ideal material for heavy prescriptions. Thin polycarbonate lenses correct poor vision beautifully without distorting the face or the size of the eyes, yet this extremely thin lens is virtual indestructible, an important safety factor for children and active adults.

Polycarbonate lenses are also used in quality sunglasses that incorporate filters to block ultra-violet (UV) rays and near-UV rays. The lenses can also be polarized to block glare, and their high impact resistance makes them perfect for sports. Many sunglasses manufacturers choose polycarbonate because it can be easily shaped without problems like cracking or splitting, resulting in extremely lightweight, distortion-free, fashionable glasses that feature all of the health benefits doctors recommend.
What is Polycarbonate?

Someone else with your problem:

Eyeglasses - lens edges keep cracking? - Yahoo! Answers

I'd demand to speak to a regional manager at Lenscrafters, not just the person who runs the place where you purchased your specs. You shouldn't have to pay for shoddy work. Good luck!
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Unread 02-09-2011, 08:57 PM
 
Location: Arizona & Wisconsin
4,587 posts, read 4,933,539 times
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Take them back. My guess is that you have AR coating on the lenses and that the coating is cracking, not the lens itself. The AR coating can be cracked because it is less flexible than the polycarbonate lens. It's usually a workmanship defect from the edging process, although it can occur in a couple of other steps. The cracks can grow over time.

It sounds as if you are caring for the lenses well. Use room temperature water, soap, and your fingers to clean them. I never, ever use anything to dry lenses with AR coating. I just blow the water off with my mouth or a can of compressed air that you would use for electronics (obviously don't invert it). If there are any marks, they get washed again until the marks are gone, but the lenses are never touched with anything but water, soap, or my fingers.

Be careful not to torque (apply turning or differential pressure) on the glasses. Although AR coating is tough, it is more brittle than the underlying than the polycarbonate, so what does not harm the lens, can harm the layers of coating.

My guess is that the lab will redo the lenses for you, or at least they should. If the cracks are cracks and not scratches, then it is most likely a workmanship defect.
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Unread 02-10-2011, 05:06 AM
 
Location: Tampa, FL
2,638 posts, read 4,985,877 times
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Quote:
Be careful not to torque (apply turning or differential pressure) on the glasses.
I recently ordered new glasses and brought my old pair in for adjustment because they really needed it. The associate pointed out to me a tiny crack that had started at the edge of the poly lens near the temple/armpiece. And suddenly I remembered one day when they were just driving me crazy and I yanked them off my face and twisted them, trying to straighten them out, and heard a snap. I inspected them at that time and didn't see any damage, it took awhile for the crack to make it out past the frame to be visible.
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Unread 02-10-2011, 01:04 PM
 
Location: Victoria TX
37,603 posts, read 31,193,090 times
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I know mine is a crack. If I look straight at it, it is invisible, but if I tilt the glasses so the crack is at an angle to line of sight, I can see the width of the crack, which goes all the way thorugh the glass. The coating is coming off, too, giving the outside surface of the lens a gritty texture, but that's a different issue. However, I am not complaining, because they are about 8 years old.
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Unread 02-21-2011, 12:09 AM
 
Location: Northeast Tennessee
6,870 posts, read 12,564,086 times
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Thanks for the replies. No, they were definitely cracks, not cracks in the coating.

To update, I took the glasses backa few days ago. When I walked in, the lady was there that sold them to me... "need and adjustment"?, she said as she happily smiled. I said, "no, the lens is cracking". She looked stunned, her expression changed and said she was sorry and they would replace the lenses, but would take a few days to get them in. It had not only one crack coming up from the bottom, but two other cracks as well over from that main crack.

I have been wearing my old glasses, so I was patiently waiting. I went back this evening and took them in... they replaced the lenses. The guy that was there that does the work said it was rare for them to crack and said it was possibly a "stress" crack or simply a defective lens. The other was not cracked, but I think they replaced them both. They said nothing about me not using dish soap and warm water to clean, which is what I have been using. It puzzles me though that my last glasses did this as well, but 17 months after I purchased them... BOTH lenses have cracked on them, but on these new ones, it took less than three weeks for cracks to appear.

I have read some stuff online where it says not to use dish soap, as it has agents that will crack the lens, while most say warm water and dish soap is fine. I dont see how the warm water and dish soap could cause it... you would think they would be designed better to prevent this. I have such oily skin, I dont think anything else will get the frames and nose pieces clean other than soap, so I will use that again on these and hope for the best. No one else I know has had problems washing their glasses with soap/water. I have been using "Joy" anti-bacterial dish soap... should I try something else?

Well, they are under warranty for 14 more months, so I guess if they crack again, they will go back again. I hop
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Unread 02-21-2011, 08:57 AM
 
15 posts, read 37,426 times
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Hi there,
Generally i'm just a browsers of these forums, however I am a licensed Optician so may be able to offer some insight.

the problem here, I am 90% sure, os because of the lens material. Polycarbonate lenses do have a tendency to crack. They are safety lenses in that they won't outright break, but the lens material is actually quite soft, it pits and cracks fairly easily. This is especially the case in Rimless glasses (where it will certainly crack at the drill mounting) or when the eyeglass lens was cut too large for the frame. The added pressure on the lens will cause this cracking.
Dish soap isn't the best to use, but it will certainly not create any chemical reaction causing the lend to physically crack. It may affect any AR coating you have, but not crack the lens.
This is certainly a lens defect, as a result of a lab error. They would be absolutely responsible for remedying this.
If you are looking for a safety lens, or slightly thinner lens I would recommend a material called "trivex" some companies will also call this "duralite." It is about as thin as Polycarbonate but significantly stronger and will not crack. If you have a rather strong RX, I would recommend a 1.67 High Index lens for it's thin profile as well as strength. If none of these apply, the simply CR-39 lens would suffice.
Any further questions please feel free to ask.
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Unread 02-24-2011, 12:40 PM
 
Location: Utah
4,026 posts, read 7,276,406 times
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Thanks for the info.

I had the right poly lens crack in the same place in two different lenses in the same frame within 2 months of buying the lenses. The frame was enclosed meaning not frameless at the bottom. The glasses were worn as a secondary vision source and only while I was home lounging around or cleaning house. No children had access to them nor any pets. They were never sat on nor dropped onto a hard surface. Both of my right lenses had NO prescription in that at all!

Bought new frames 3 months ago and the new lenses are holding up just fine so far. The right lens now has a -.5 Sphere which I guess is the strength of my prescription.
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