What is causing a single vision Crizal Avance lens to craze?

[Happylady]

This woman has had two pairs of lenses craze. The first pair was after about 10 months. She was told it was probably heat (early October and it is still hot here). Almost exactly a year later the replacement pair has crazed. They look like they have wavy lines running across them. She picked up another pair a couple of days ago.

Her rx is very light and the material is plastic. They are in a full metal frame. She swears she does not leave them in the heat and only uses the microfiber cloth to clean them. She never uses any products on them.

I think I've heard that crazing can be caused by the flexing of lenses and AR being different. A very thin lens like he has could have this problem. I think I've also heard it can be caused by a too big lens in a frame.

Anyone have any insight? Could one of these be the problem? Or any ideas of something else? If so why does it take so long to show up?

She is concerned that it will happen again and her warranty is up in 3 months.

[uncut]

Look for transient sources of heat, like barbecues, campfires, stoves/fireplaces. Occupation causes may include pizza ovens, welding units. I have had people toast lenses by leaving them in cars on super hot days. Thicknesses below 2 mm are highly susceptable to pressure/flex and infrared source damage, IMO.

[Happylady]

Look for transient sources of heat, like barbecues, campfires, stoves/fireplaces. Occupation causes may include pizza ovens, welding units. I have had people toast lenses by leaving them in cars on super hot days. Thicknesses below 2 mm are highly susceptible to pressure/flex and infrared source damage, IMO.

She told me she just uses them in the house for reading and computer.

I didn't think about the flex problem until after she left so I didn't measure the centers but it's a very light rx. Have you seen problems with thin rxs? I so rarely see a Crizal craze.I honestly can't remember the last time.

[uncut]

Betcha she uses them when she's using a hairdryer, as well as near her barbecue.

[optical24/7]

Ever open an oven to check a cake? I say heat also. ( you can tell if the lenses are too big by just taking the eyewire screw out and press the eyewire closed by hand.)

[sharpstick777]

Ground lenses are more prone to crazing, due to slight changes in the substrate caused by uneven tool pressure. Heat is the primary cause, substrate changes are the second most common cause of crazing I see. Crizal is more prone to heat damage than other AR's. Do you use a salt pan? I recommend hot air only with Crizal, especially with Crizal on Poly, 1.67 and Trivex.

It can sometimes take a year for crazing to become evident after the damage has been done so its often hard to pin point the source.

If the crazing is just in the center the likely culprit is or the tool/lap is worn slightly when ground, or heat from a salt pan (where the lens is thinnest and can't absorb the heat as well).

If it's on the outside only, the culprit is most likely stress from being oversize (hold it under a polarized lens to look for stress marks).

If that patient is exposing it to heat (cooking, BBQ) the crazing is more likely to be even across the lens.

See if you can have the lenses processed on a digital generator for more even surface pressure, or switch AR's.

[chip anderson]

Geeze, and I was just hopeing that Zeiss would get coating that held up as good a Crizal.

Chip

[anthonyf1509]

Geeze, and I was just hopeing that Zeiss would get coating that held up as good a Crizal.

Chip

I read alot of Crizal product horror stories here.
It's been great, best AR s we've tried and kept.
Recently experimenting with Zeiss due to a new lab availability and sorely disappointed with the AR only.
We'll get the occasional craze but few and far between and can't beat their warranty

[DragonLensmanWV]

I gave up on Craze-All.

[Uncle Fester]

Vapor from fingernail polish remover?
Just a thought.

[sharpstick777]

Two other issue is whether the hard coat is thermally or UV cured. UV curing does not penetrate entirely through the coating, so some catalyst remains unreacted. With each micron of coating you gain some degree of UV loss. With thermal/heat curing, you get a higher percentage of fully reacted catalyst as heat will penetrate through the entire coating.

If you are having trouble with your Crizal, find out whether your lab uses UV or Thermal curing of their hard coats.

I have also seen the Crizal tends to be more sensitive to proper Degassing than other AR's. Degassing is when the water is taken out of the lens through heat before the coating process. If any moisture remains, it could be detrimental later. If the lens is warmed with trapped moisture it can cause crazing months or years down the road.

[optilady1]

What about going in the pool? I know she says she only wears them in the house, but plenty of people wear them in the pool to read, and you say you live somewhere warm....

[Uncle Fester]

What about going in the pool? I know she says she only wears them in the house, but plenty of people wear them in the pool to read, and you say you live somewhere warm....

I tell the story of a patient who's shoulder injury required hot tub therapy and on the 3rd visit found his lenses crazed from the chlorine vapors.

[icmor]

Are they stock sv lenses? Our experience is that they are thinner than most lenses, and have had more crazing problems due to thin lenses. We stopped using crizal stock lenses altogether. Check with your lab if you did not edge them; they may have used stock lenses rather than surfacing them.

[chip anderson]

I remember Chris posting a lot of things that eat AR but I don't remember chlorine. Is this toxic to AR?

Chip