Should Abbe value be the last thing considered (or even be considered at all) when selecting lens material? Is it true that only a small percentage of the population is "Abbe Sensitive", or is it that opticians are just bad at diagnosing Abbe sensitivity? Has anyone seen studies on this topic?
Abbe should be considered for:
rx's requiring a prismatic correction over 3 prism D
multifocal rx's, especially plus rx's
"eye-turners" in rx's over 3 D
Anyone over 6 D
I'm sure there are more, someone chime in!
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
I'm no where near as technical as Wes, but:
anyone switching out of glass
anyone going backwards into poly
and I would lower the 6D criteria to around 4D
Anyone who says they loved their glasses from 2 years ago, but the ones they've had for a year never "felt" right, and you can't see any obvious reason why other than a material change.
Anyone who has glasses from the evil empire and can't see. Put them in anything else and they will love you forever.
Well corrected FFSV lenses remove so many layers of lateral optical errors that many formally intolerant of poly people might actually find them and their abbe ok.
Besides, I think it has been poor poly lens quality that is also at the root of poly dissatisfaction.
B
I based my statements on chromatic aberration which Abbe represents. While proper FreeForm design can compensate for power error, radial astigmatism and the like, it can do nothing to correct shortcomings in the properties of the material itself, only the design. Therefore, chromatic aberration is the one issue FreeForm designs can't address.Originally Posted by Barry Santini
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
We used to say "A/R the heck out of them", but that never really solved the overall problem, especially on the 1.806 glass.
Chromatic abberation is the major beast IMO, and is often the root of patient dissatisfaction. "Everything has a rainbow around the edge of it."
Uilleann -- but what the article DOES NOT cover is how to convince your patients to stop looking "off axis". I agree that straight on through the lens is not an issue, that it is always off-axis viewing. However, when a person has become used to using the entire lens to look through, what then? I think that this is where the major problem has been, patient education and/or patient resistance to changing their viewing habits.
Mythical creature or not, I know that for ME, I see better out of my plastic lenses than my poly. I don't know if it's psychological or not, but they are much clearer in the periphery. I'm not very picky, so if I sniff out a picky patient, I try to get them into trivex or plastic.
Oh, and all the technical answers that Wes said.
Agreed, Wes. But all the errors, including the ones you cite are layered on top of each other, creating a recipe of dissatisfaction.
Since FF lenses excel at peripheral improvments, they can reduce the contributions of these layers, maybe leaving lateral color error to be not as much of an issue.
Suggested test:
Optigirl:
Make the same Rx (yours) in both poly AR and trivex AR in the same frame and same FF optimized lens design (I favor Individual for minus Rxs).
Then let me know what you think.
Barry
I can tell the difference, even in suns, between materials. I don't like looking through Poly or 1.67 at all even in a -1.00, everything looks cloudy and washed out. Although many of our patients won't know the difference, some will. It should still be a huge consideration at every dispense, with every patient.
Are we only just after Visual Accuity based on an eyechart? Quality of life is higher if colors come through more vibrantly.
Thanks for all your input everyone. Barry - I saw your comment last night was was wondering along the same lines. This opens up a whole 'nother' can of worms to think about - I was guessing formulas for calculating chromatic error are going to have to be dragged out to some degree. How much is induced by index and how much from angle of incidence, ect... I'm looking forward to the research, or hearing from someone else on this topic.
This also leads into another question, which is: Does applying A/R assist in reducing Chromatic Abberation, or in other words, modify the "effective" Abbe value?
Adding AR might give you a clearer rainbow.
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
Lately I've had glasses made in mid-index, poly, and 1.60. Sorry to say, I don't see a difference. My Rx is about. -3.75/2.50 add. Cr and trivex feel good too, but are thicker.
Many men have a lower color perception than woman in general, and people just differ. Many patients can't tell at all, and some are super sensitive. I had a +.50 sphere pt non-adapt to Trivex once. It was strange, but sensitivity can vary, but a higher ABBE material is just one less thing you have to worry about.
I think this is the real key. Everyone is soooo different. I just made a new pair of glasses for a guy whose lenses were so crazed that I couldn't get a reading on the lensometer, but he swears up and down he sees great out of them. Then I've got my patient who spent over $700 on silhouette driving glasses, for a
-.25 sphere ou. Twice, because he lost the first pair.
I will admit ABBE doesn't play too much into the reason for why I make the decisions that I do. Typically I choose materials that will be more durable or hold up better in a certain frame. As for myself, I choose plastic many times because it's cheaper, and I don't want to spend a lot of money on my 5th or 6th pair of the year.
Optilady: You really got to learn that all lenses except glass and quartz (or "mineral" as they call it across the sea) are Plastic. This includes CR-39, Poly, Trivex and the latest miracle.
Chip
Yes dear chippy, I am well aware of this fact. In the cool new optician vernacular though, most of us in our gang understand plastic to mean CR-39. Next time I will speak for both us youngsters and foot note it for you pillars of the community as well.
Count me among the weird sensitives. I'm a -5.75 -1.50 OD, -7.25 -2.00 OS. Can't do poly, but it's not specifically the CA; they just feel weird, like my eyes are having to work harder to focus. 1.67, however, is perfectly comfortable, as is 1.74. However hard I try, I simply can not see the CA rainbow everyone talks about. I'm wearing my biggest frame right now (a John Varvatos 348) with the cheapest 1.67 stock lens I've ever bought, non-FF, with Viso XC A/R, and no matter how off-axis I look, I don't see a darn thing other than the amount of peripheral distortion I expect to see 20+mm away from the OC. My brother, on the other hand, is less than a -2.00 OU and sees the CA all over the place.
I'm Andrew Hamm and I approve this message.
I understood you that way too. Most of the people in my lab have that understanding. Some of the newbie opticians at our accounts do not though. lol.
I think plastic and trivex have the best clarity. I may be biased though, I love trivex material. Don't care too much for poly.
-"Is this a matter of life or death?"
---"No. this is a seg height."--Seth, and Dalene
"In matters of style, swim with the current;
In matters of principle, stand like a rock."--Thomas Jefferson
Hi - if the Trivex material was made correctly - to approximately a 1.5 CT, the thickness should have been about the same as your 1.6 or poly - especially for a -3.75 Rx.....
For what it's worth I can't stand it when motorcycle "builders" call a transmission a "tranny" either.
We loose a lot when we put slang to technical things. Had an otherwise excellent receptionist that we could never break of calling a lens "a len" or a temple "a leg." Irritated all us Opticians but she was good at her job.
Chip
Actually, they're hard resin materials of various types.
Hard resin don't be a plastic?
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