abberation help?

[Bok]

Hi guys,

Just wondering a client of mine today has bought back their specs as they are getting rainbow colouration effects on the edges of the lenses.

rx is
RE: +0.25/-0.25x180
LE: +0.25 DS
ADD: +1.75
Dispensed Sola One HDV 1.5 index with brown sunglass lenses LTF 18%

PD is 30mm R+L and Height Seg is set at 28mm above rim,
A:52mm
B42mm
ED: 60mm
DBL: 18mm

Why is this client experiencing the colouration?

[pseudonym]

I was going to ask if they were semi-rim with polished edges until you said it was a brown tint. Is this a full frame?

[Bok]

I was going to ask if they were semi-rim with polished edges until you said it was a brown tint. Is this a full frame?

yes full frame acetate tortoishell coloured dark black/brown mix

PD's fine, Height fine, Facial wrap and panto fine, BVD 12mm. So I am scratching my head... All I can think of is the ED is to big compaired to the OC am I right?

[Uncle Fester]

Put them on and see if you can see it too.

If you can see it shade with your hands the top, sides and bottom to see which direction the light comes from to cause this effect. Or get the patients response to this trick of the trade.

Also from wiki-


Stress induced birefringence


Color pattern of a plastic box with "frozen in" mechanical stress placed between two crossed polarizers.


Isotropic solids do not exhibit birefringence. However, when they are under mechanical stress, birefringence results. The stress can be applied externally or is ‘frozen’ in after a birefringent plastic ware is cooled after it is manufactured using injection molding. When such a sample is placed between two crossed polarizers, colour patterns can be observed, because polarization of a light ray is rotated after passing through a birefingent material and the amount of rotation is dependent on wavelength. The experimental method called photoelasticity used for analyzing stress distribution in solids is based on the same principl

[Randle Tibbs, ABOM]

With the amount of vertical decentration to achieve that seg height, is it possible they could be experiencing lateral chromatic aberration?

[DanLiv]

Stress induced birefringence

I would guess this too. Given the low Rx and high Abbe 1.50 chromatic abberation would be low.

Are these tinted or polarized? Uncle Fester, if they are just tinted how would the cross polarization needed to reveal the birefringence occur? If they are polarized, there you go, just looking through any auto glass will produce the cross polarization effect. But non-polar?

[Uncle Fester]

Uncle Fester, if they are just tinted how would the cross polarization needed to reveal the birefringence occur?

good question!

Anyone?

[Judy Canty]

a polariscope.

[Trip]

A polarized light source (lcd monitor) and then a polarized lens ....

[DanLiv]

A polarized light source (lcd monitor) and then a polarized lens ....

Yes, that's going to produce cross polarization effects in any pair of glasses. Presumably that's not what's going on here, unless the OP is unfamiliar with cross polarization. The patient seems to be complaining of peripheral color distortion, and presumably all the time not just while looking at polarized light sources.

If the lenses are polarized, perhaps the interaction of the polarizing filter and bifringence in the lens is producing crosas polarization in the lens intself, and that would explain the constrant effect, as well as being limited to the peripheries when the lens is most stressed.

If it's not polarized, then dunno...

[rdcoach5]

Hi guys,

Just wondering a client of mine today has bought back their specs as they are getting rainbow colouration effects on the edges of the lenses.

rx is
RE: +0.25/-0.25x180
LE: +0.25 DS
ADD: +1.75
Dispensed Sola One HDV 1.5 index with brown sunglass lenses LTF 18%

PD is 30mm R+L and Height Seg is set at 28mm above rim,
A:52mm
B42mm
ED: 60mm
DBL: 18mm

Why is this client experiencing the colouration?

Because the dye is penetrating the edge more since the scratch cote has been edged off.