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For the ODs/progressive wearers, blue glare with new progressives?
June 21, 2012 12:01 PM   Subscribe

I did not get an answer from my optometrist/optician so I'm turning to the hive. Just got a new pair of progressive lenses and find that outside the central clear zone there is a blue shift/glare at the border of lights and corners of illuminated objects. More inside...

I recently received a new pair of glasses:

They are Zeiss GT2 progressive 1.67 High Index with AR coatings, and I have astigmatism.

Except for the clear vision area near the major reference point, I find that I see "blue light" glare at the edge of any lights, or sharp corners of objects when there is a light source close by illuminating them. For example, the entire edge of a kitchen's fluorescent light will have a bright blue border, or the edge of a window blind will have it during the day.

I do not have this problem with my old pair of progressives or contacts, nor does it happen when I'm not wearing glasses.

I had the lab send a new lens, and it has the same issue although the exact area where it exhibits this property is not the same as the first lens.

Could anyone point me to a resource or provide some insight? Thanks!
posted by palionex to Health & Fitness (8 answers total)
 
What's happening is the light is refracting less/more if it is red/blue.

I think all lenses do this to a greater or smaller degree, since they are real world objects with whose refractive index varies a bit depending on color.

Normally, when I get a slightly higher prescription than my old, the phenomenon is stronger and therefore more noticeable.

If your old progressives are the same prescription, then the new lenses are made from a slightly more inferior material, dispersion wise: get a pair of the same old lens material. If you have a stronger prescription then what's happening is that the dispersion is therefore stronger too.

It may be that you may be unable to get lenses from a material that disperses less.
posted by sebastienbailard at 12:16 PM on June 21, 2012


Yes, the problem is basic physics - it's called chromatic aberration and is common to all lenses. Expensive photographic/astronomical lenses can minimize it, but eyeglasses are limited in what they can do. Your optician ought to know about this.
posted by lathrop at 12:43 PM on June 21, 2012


How long have you had the new glasses?

When I go to a stronger prescription I notice this same thing. I either adapt to it, or stop noticing it as much.

Try wearing them for a week or two.
posted by fontophilic at 1:59 PM on June 21, 2012


It's chromatic aberration. It's not a defect; it's an intrinsic property of the material the lens is made from. From this datasheet, the material in those high index of refraction (n=1.67) lenses has a low Abbe number (32), which means they will exhibit more chromatic aberration than more common lens materials. The GT2 lenses come in a variety of materials, including a n=1.59 polycarbonate (Abbe number 30), and a n=1.5 "hard resin" (Abbe number 58). I am not an optometrist or optician and cannot tell you what is actually possible for your vision, but if I were building an optical system and chromatic aberration was a problem, I would consider switching to the high Abbe (but lower index) glass. This might not be possible (I would have assumed that the optician would default to the lower-index glass if it was feasible), but I would at least ask the optician about the choice of materials. They might have chosen the n=1.67 to reduce weight or cost, and might be able to select a different material if you ask.
posted by kiltedtaco at 3:07 PM on June 21, 2012


To add to what kiltedtaco said, there is something of an arms race among opticians to make lenses lighter for marketing purposes, and what has probably happened is you're noticing more chromatic aberration to the low Abbe number of the higher basic index material. Materials have other properties which get compromised for similar reasons, such as toughness and scratch resistance. If the effect continues to annoy you I'd follow his advice to see if a different material could be used that represents a different compromise.
posted by localroger at 4:08 PM on June 21, 2012


Thanks for all the great answers! I'm marking all of them as best answer since they were all helpful. I guess what I'm most interested in is the Abbe number. How I could forget all of those physics lessons at uni I do not know...
posted by palionex at 8:42 PM on June 21, 2012


I get this with all my glasses (even those with high-index Zeiss lenses), but I have extreme myopia. I consider it a feature, not a bug -- spectrographic analysis is always available, for any local light source.
posted by Rash at 1:00 PM on June 22, 2012


Like Rash, all my glasses have done that. I'm very near-sighted, with a strong prescription.
posted by Savannah at 4:16 PM on June 23, 2012


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