Finding defects on AR lenses with a black light...

[Uncle Fester]

Very nearsighted (-8.00) patient came in saying the new sv 1.6 Avances' right lens was blurry. Several of us looked at it and couldn't see anything wrong. Sent it back to the lab and got a call back that indeed the right lens under a black light was showing crazing. I don't recall seeing a thread or post that suggested we use a uv light to check ar's so I post this for others who may not know about this.

[AngeHamm]

Ooooh. Any new tool for finding AR crazing is AWESOME.

[pseudonym]

Weird. I haven't thought about black lights for about 30 years and here they are again twice in the same week.

[Uncle Fester]

I hope I wasn't hoodwinked.

On second dispensing pts see's same problem and I see it now for the first time too!

R -6.75 -.50x 95 Left -6.75 sph. sv 1.6 Avance AR

Held up to an indoor track floodlight at a specific angle where I push the frame so the frame has the right lens away from the left so the left is closer to me at about 30 degrees, with an average panto, a crescent moon shape shaped smudge about 5mm wide appears towards the top of the lens. As I move the frame up the smudge moves down towards the OC and widens eventually doubling in size. Both the pts and myself cannot induce this in the left lens. Whether edge is polished or not the image is there.

Any thoughts?

[Wes]

Crazing from chuck pressure?

[uncut]

I agree with Wes, with a proviso that the phenomena is not directly pressure, but flexing/pressure, created during edging, clamping, or insertion/eyewire tension.

Another way to make this apparent is to use a quartz spotlight at about 15 degrees off the plane of the front of the lens. The quartz(halogen) spotlight needs to be about 10 inches away from the lens.

I have found that the centre thickness, or lack thereof, of the lens...........is a contributing factor.

[Uncle Fester]

Can't recall this as an issue in 1.6 but it makes a lot of sense and gives me something to run with.

Thanks for the replies! Optiboarders RULE!!!

[paulcr39]

Perhaps you can share this with your lab:

Corporate Quality – Technical Support

Edging Instructions for Thin Lenses and AR Coatings

With the increasing amount of thinner and lighter lenses arriving in the market place, theEssilor Laboratory Development Group has created a quick reference guide for handlingthese lenses.With the various combinations of materials, coatings, lens thickness and edgingequipment, care must be utilized in the edging process to assure optimum results.Following these procedures will ensure great results when finishing these lenses.

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All anti-reflective and thin centered lenses must be handled with care.

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Use edging blocks that match the front curve of the lens. This is most critical on theflatter base curves.

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The front and backside chuck shapes must conform so there is no flexing of thelens.

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Apply an edging enhancement tape protector to both surfaces of the lens prior toedging. This will help prevent slippage and gives a better surface for the edgerchuck to grip.

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Be sure all wheels and blades are clean and sharp.

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Ensure edger clamp (chuck) pads are clean.

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Edger clamping (chuck) pressure must be set to the least amount recommended bythe machine manufacturer.

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When possible, reduce the edger head pressure and feed rate.

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Utilize the continuous lens rotation mode if available. (Contact your machine supplierif this function is not available…sometimes all that is needed is a software upgrade.)

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Assure exact sizing; leaving lenses large creates unwanted stress on the lens.

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After the edging cycle, rinse lenses immediately in clean water and carefullydeblock. Be sure to twist the block off rather than prying. “Do not flex or bend the lens during deblocking or at any other time”

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Apply light pressure at all times when handling the lens during beveling and mounting.

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Avoid the use of lens alignment pliers.

For Technical Assistance

1-800-377-4567 ext. 7197