Blue outlines??
I am new to this site, but was wondering if i could rake all of your "all-knowing" minds...
I have a patient who was fitted into a Definity PAL and she is now seeing a faint blue outline on objects outside. (she may be seeing it indoors as well, but did not mention it.) Is this due to coatings, or is this an effect of the Definity...
Any input is welcomed...
Erica
What material?
It was a Definity in regular 1.5 center thickness poly with transitions and a crizal alize' with clearguard a/r. any ideas??
Last edited by SummitVisionCenter; 09-20-2006 at 05:11 PM.
Poly!
I'll second Chip:
Fezz
:cheers:
I have to agree! Since it's polycarbonate that's really the first thing to consider as the problem. You're trying to furnish your patient with a better product/lens design - but order it in polycarbonate??
Don't listen to the above post.
Polycarb's optical (not mechanical) problems are power dependent. How high are her powers? That's the "rest of the story".
Remember, poly-bashers:
1.67 is just as bad
Traditional 1.6 is not much better
If you want to make significant differences in abbe, you have to lower the index down close to 1.5, away from 1.6, meaning that the lenses must be thick...
My experience says: only certain people are sensitive to abbe, and of those, we only know about the ones that have high refractive errors (because they have the opportunity to notice). They are a group that will have to choose between cosmetics and optics (a familiar trade-off).
So, yeah, Definity's great design is mitigated somewhat by high index lens use, but her power had to be great enough that you needed a high index for cosmetics and physical properties.
Remember, a great progressive design in poly beats a mediocre progressive design in poly, so it's an illogical argument to not use poly or high index for high-tech progressive designs.
Heck, remember! Even the "highest-tech progressive design" available is a significant departure from good optics! If good optics were such a premium, we shouldn't use a progressive!
And don't forget those fashion accommodations that we are always making!
Compromises are made to fit the needs of the situation. We are designing optics for people; we are not designing space-based telescopes.
Opticianry and optometry are about applying optical principles and devices to people. We deal primarily in people, not optics.
We're in the "applied optics" field, like the telescope designer, but we have a tougher end user to satisfy.
Bottom line: explain the facts, ma'am. If she can't hack it by one week, remake that big spender to 1.5, and it will diminish.
Last edited by drk; 09-21-2006 at 08:36 AM.
Quote:
"Polycarb's optical (not mechanical) problems are power dependent."
I wouldn't think you'd be ordering Definity for a lower power prescription. I wasn't knocking the lens, but I was questioning the selection of polycarbonate for this Rx. "DRK" used a lot of words to say it but seemed to agree that the selection of another material might solve the problem.
Added:
Remember that polycarbonate has problems beyond its low abbe value. The material is soft and 1.0 poly can easily warp when mounted in a frame. Polycarbonate lenses have tons of birefringence stress. This can vary a bit by manufacturer and from lens to lens. Birefringence is a manufacturing-induced “stress” distortion, a result of the injection compression molding process used by virtually all polycarbonate lens makers.
Birefringence stress causes optical errors (distortion/power variations) throughout the lens. It's just not a good thing....
Last edited by Bill Mahnke; 09-21-2006 at 10:37 AM.
Another thing to concider especially in poly, not that you can do too much with this in a progressive, is the height of the vertical (distance ) center. Too often the vertical center of the distance power is not concidered. Believe me it it's off very far from the "as worn" center, all sorts of colors can outline everything. However Reds, and yellows have been more likely to be indicators of this in my missadventures.
Chip
Originally Posted by Bill Mahnke
:bbg:
Fezz
:cheers:
Doc, you've got my vote! I wish more L.D.O.'s, O.D.'s and, God forbid, M.D.'s (no holding of proverbial breath here) paid as much attention as you.
A quick note regarding birefringence: I certainly hope all of you are bevelling your lenses according to the base curves of your selected frames or at the very least are manipulating the frame to match the b.c. of the BEVEL of your lenses. This adjustment, of course, should always be done regardless. Even the best of your biref.-free lenses aren't worth diddly if you just glaze them without these considerations. Conversely, some of the lousiest stock poly lenses can perform quite well if you do take this added step. You certainly can forget about any PALs performing their best if you don't.
I'll say thanks to all who take the time to post here. This is an incredibly valuable resource and should definitely be talked about more among ECP's.:)
Peace out...
Kyle
I agree that poly is the problem. this is normal and I am not bashing the material just spouting my opinion. Yes you can get this with all materials. I can make fluorescent lights edges turn blue to yellow by turning my head. A dollar says your patient can do that also. Let her try and switch material is she can't hack the color.
Sound like POLY Problem.
Marcy Apple, ABOC
"Dance to the music of your dreams...the steps will bring you joy"
A simple test would be to ask the patient to see a monochromatic light source ... like a tube light or even a window from where some sunlight is filtering in ...
Can you see the upper part of the tubelight as blue-ishand the lower side as having a yellow-red tinge ? ( You should try this your self ..ideally with a - 6.00 diopter Poly) .. :hammer:
If the patient confirms ... YES !!!!
It indicates a sensitive type who has a keen eye for color details..
This type of patient should NEVER be given poly as he can clearly percieve this color shift that poly induces in most prescriptions..:finger:
I personally feel any abbe below 40 will be rejected by such a person.
Good post.
Post not needed. Misinformation. I goofed!
Last edited by Fezz; 09-22-2006 at 10:13 AM.
I agree poly is the problem. Just my two cents, I've used definity as a primary lens since it came out (at an office which equates poly with the devil) so we've always used plastic and hi index) and in, what is it now, two years? I've NEVER heard a complaint. So, I can vouch that it's not because they are definity.
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