rimless frame and CR39 chipping

[ilanh]

I just had a patient come in twice with a pair of Cazal frames (that she bought elsewhere) and lenses that she bought from us. The lenses are trifocal CR39 and tinted. The left lens chipped a few months ago and we had to replace it. She is in again today for a small chip in the right lens. Both chips occurred right at the eye wire and very close to the bridge. I noticed that the grooved eyewire is a bit disrupted as it goes up into the bridge (and was wondering if she knocked the glasses). In either case, it seems to me that the job should probably have been done with poly or mid to high index instead of CR39. Her Rx was:

+2.00 with 2.50 add OU

Would appreciate any feedback,

[For-Life]

The frame might be a little harsh on the bridge. That would be the thicker point of the lens for her, so something had to happen.

I had a cover girl a few years ago that was harsh on the temple side. I switched to poly right away.

Did you feather both sides of the lenses when you edge them?

[slaboff]

for that script i would have done trivex... in a shamir genesis.

[Chris Ryser]

In either case, it seems to me that the job should probably have been done with poly or mid to high index instead of CR39.

It does not matter what lens material you use................glass........flint glass...............CR39...........Polycarbonate............ ....Trivex

When the job is not properly done like sharp edges.......tension in the wrong place you will get chipping on CR39 or cracking with Poly or other materials.

Tell the guy's in the lab...........wherever it is to take some lessons in rimless mountings and replace the damaged ones.

You also should be able to see if they have been properly done.

[Jedi]

We rarely do any drill, nylon goove, metal groove in CR-39. I've personally seen too many poly drills crack, even Maui Jims (Chris you should call them). Use a 1.6/ 1.67 (most have a warranty from the supplier), or trivex.

[For-Life]

I do a lot, and I mean a lot of grooved rimlons. I have very, very few problems. If I do have a problem it is usually the frame, the lens being too thin, or the customer did something really bad.

If you groove and feather it properly you should have very little trouble.

[Jedi]

or the customer did something really bad.

But, they are always in the case, and I only touch them with white gloves and the just fell to pieces.

[OPTIDONN]

I just had a patient come in twice with a pair of Cazal frames (that she bought elsewhere) and lenses that she bought from us. The lenses are trifocal CR39 and tinted. The left lens chipped a few months ago and we had to replace it. She is in again today for a small chip in the right lens. Both chips occurred right at the eye wire and very close to the bridge. I noticed that the grooved eyewire is a bit disrupted as it goes up into the bridge (and was wondering if she knocked the glasses). In either case, it seems to me that the job should probably have been done with poly or mid to high index instead of CR39. Her Rx was:

+2.00 with 2.50 add OU

Would appreciate any feedback,

If the rx is a +2.00 with an add and there is chipping towards the nasal I think that the lenses are being made too thin. The only time I have the edges chip is if I surfaced the lens too thin and make the groove too deep.

[OPTIDONN]

It does not matter what lens material you use................glass........flint glass...............CR39...........Polycarbonate............ ....Trivex

When the job is not properly done like sharp edges.......tension in the wrong place you will get chipping on CR39 or cracking with Poly or other materials.

Tell the guy's in the lab...........wherever it is to take some lessons in rimless mountings and replace the damaged ones.

You also should be able to see if they have been properly done.

Couldn't have said it better!! Screw up enough in a lab and you soon see that its not the material its the way its made.:cheers:

[For-Life]

But, they are always in the case, and I only touch them with white gloves and the just fell to pieces.

lol

I had someone in today. His lenses crazed.

When he asked me what happened I just sucked it up and said it could of been a problem with manufacturing, but that extreme heat or products like windex could have also caused it.

I then looked like I was accepting blame, but also awaring him of what to be careful of. He then admitted that he left his glasses in the windshield of the car.

[ilanh]

Thanks guys,

Excellent advice all around. I think that I will start using Trivex more frequently now that it seems more widely available. From the posts I have received I now feel less bad about asking the lab to remake these.

ilan

[Chris Ryser]

lol

I had someone in today. His lenses crazed.

He then admitted that he left his glasses in the windshield of the car.

Hard coats on lenses can craze in extreme heat or cold, when the expansion or contraction coefficient is different...................which means the lens material expands more or faster than the hard coat in extreme heat like a under car wind shield.

You should warn the customer at point of delivery when selling hard coated lenses as well AR coated lenses which contain a SIO2(silicon dioxyde = glass) layer that is NOT flexible at all.

[rsandr]

Hard coats on lenses can craze in extreme heat or cold, when the expansion or contraction coefficient is different...................which means the lens material expands more or faster than the hard coat in extreme heat like a under car wind shield.

You should warn the customer at point of delivery when selling hard coated lenses as well AR coated lenses which contain a SIO2(silicon dioxyde = glass) layer that is NOT flexible at all.

Sorry if im too far off topic, didnt seem worth a new thread....
Do you know of a dip hard coat that is adequate for coating polycarbonate lenses after surfacing.
We only surface CR39 at the minute and I would like to have a dabble with poly. I dont want to spend thousands on a UV cure coater until I fully subscribe to the idea.

Rick

[Chris Ryser]

Do you know of a dip hard coat that is adequate for coating polycarbonate lenses after surfacing.
We only surface CR39 at the minute and I would like to have a dabble with poly. I dont want to spend thousands on a UV cure coater until I fully subscribe to the idea.
Rick

Any coating can be applied by spinning or dipping.

UV curable coatings come in many different wariations. The hardest ones are not tintable...............the more tintable, the softer the finished coating gets.
However if the lenses should be AR coated, UV curable coatings do not provide the best adhesion for AR coating materials.

In that case you should look for polysiloxane silicone based) materials which are more compatible with AR coating materials.

[LENNY]

Polish the edges!
Works amazing for me!
Almost elimanated all chipping and looks better.:cheers: