Damage to coatings

[Falstaff]

I am interested in how the damage that is sometimes seen on returned lenses evolves. For example, how the different patterns of crazing and scratches might eventually cause delaminated areas.

In particular, it would be of assistance to us to be able to distinguish between lens abuse, by the customer, and possible processing faults in the dip or vacuum coating. We realise that no exact forensic science probably exists for damaged coatings, but there appears to be remarkably little information accessible through the web or text book literature.

Can anyone point us in the right direction please?

Thanks

[Mizikal]

When I look at scratched lenses and all the scratches are in a circle that is usually a good sign that it is abuse.

[tdj]

Scratches on the most convex spot on the front surface in a small area are usually an indication that the pt puts down the glasses lenses-down.

Little "dots" on AR coated lenses are usually an indication that the pt is putting on hairspray with the glasses either on or in the bathroom with them, especially women.

If you have a pt in poly who continually is coming back with cracked lenses, and you've made sure the lenses are sized correctly, ask them what they do for a living. Nail techs, for example, work around so much acetone that this is fairly inevitable -- get them out of poly.

[Geirskogul]

AR coatings are rated in "boils" on how durable they are to heat, as far as I understand. We had a patient who had many remakes on his Teflon AR coating (unlimited crazing remakes from Zeiss) and eventually we got out of him information that he was showering in his glasses. Asked if he would not do that, replied no, so we remade his glasses without Teflon.

He had the same problems 5 years ago when we used Crizal or whatever, but never got around to the root of the problem.

[Craig]

If you cannot feel the scratch or ding with your nail; it is defective. We replace for 2 years if lenses are otherwise in great shape or 50% if they are marginal after year one.
We have almost no scratched lenses with even less defective product. Our returns are less than 1% and so is that of Pech Optical. If the system used is good, there should be almost no returns for any reason. We have most failure on transitions products with polarized next, but we almost never have a defective mirror coating.

Most time what folks think are circular scratches is actually a coating failure. You need to look and also determine which side is failing, most times it is the backside that is having an isssue and the patient cannot really scratch the back of the lenses.