Poll time, again!

[drk]

I'm losing my confidence on lens design for high minus! What would you do, and why?

[Jedi]

To paraphrase your question, "best bang for the buck", I chose the ultra-high index aspheric, but I should clarify, I would choose 1.67 not 1.74. Like all orders decentration and frame size will narrow down the"best" choice.

Unless the patient has vision in one eye only, I would rule out poly, unless your patient likes looking through a dime sized area :) .

[Texas Ranger]

I chose the 1.60 aspheric, best for the cost.. I would get Pentax's finished lens with AR, have it tomorrow, done deal. I do like the 1.67 aspheric with Crizal Alize, but it's more $$. So, if it's a CL lens wearer and they're not worn much, the 1.60; if it's the pts primary glasses, and money's not to total concern, then the 1.67 Alize, but in either case, I would let the pt choose. given the pros and cons of each...

[Pete Hanlin]

I voted polycarbonate... As a former -4.75 myope, I wore polycarbonate with no complaints. If vision through a polycarbonate lens is limited (especially if the limit of clear vision is only the central 25-28 degrees of the lens, which is about the size of a dime), I would seriously examine the surface quality of the lens. Since the abbe values of poly and ultra high index products are practically equivalent (both in the low 30s), there should be very little difference in the optical performance of these materials. Even so, chromatic aberration has a minor effect on vision for most wearers- you need to be looking through substantial prism to experience levels high enough to disturb vision.

Anyway, for the $ (and that was the question asked), I would suggest that the poly lens will be only marginally thicker than a 1.67 lens- and the weight will be very close to the same.

[Texas Ranger]

Pete, the poll results up there don't show that anyone voted for spherical poly, so was your vote for the aspheric, atoric poly? then i don't think that's the best $$ deal?

[Robert Martellaro]

For the best "overall" performance I would choose the atoric_1.66_abbe_32 Vizio by Sola.

For the best vision I would consider a cast atoric _1.56 abbe_40 from Optical Dynamics, although the lower abbe is less of a factor with single vision lenses where there's a much shorter reading depth than with multifocals.

Robert

[Jedi]



If vision through a polycarbonate lens is limited (especially if the limit of clear vision is only the central 25-28 degrees of the lens, which is about the size of a dime), I would seriously examine the surface quality of the lens. Since the abbe values of poly and ultra high index products are practically equivalent (both in the low 30s), there should be very little difference in the optical performance of these materials. Even so, chromatic aberration has a minor effect on vision for most wearers- you need to be looking through substantial prism to experience levels high enough to disturb vision.

Pete,
I'll the first to admit that I haven't fit much polycarb in the two offices I've worked in over the past 5 years, i'm basing my statement on personal experience and patient response from a chain I worked at before, that PUSHED polycarb. At that time I did experience many complaints in powers over -4.00 and with higher cyclinder powers. At a -2.00 -2.00x180 ou I am much more comfortable in mid-index and high-index aspheric than I ever was in poly.

[chip anderson]

Don't care what anyone tells you, use 167. Never use 166 you will end up eating 80% of them when the coating breaks down in 11 to 18 months. When patients spend this kind of money for lenses they expect the product to last. I know many of us assume that the patient will have an Rx change in 12 months every year, but patients see things from a different prospective.


Chip:finger:

[Spexvet]

1.67 will look the best by far. My second choice would be poly. Any aberation problems with poly can be virtually elminated with an AR coating (Alize, of course).

[For-Life]

I picked Aspheric/Atoric Poly, as long as the frame size and pd are average. If you look at the thickness in a frame that has a 48 eye size, a 67 frame pd, and a pd of 62 there really is no difference between Airwear Aspheric or TL 167. It all really depends on the size of the frame and the pd.

Also, remember that the -2.00 cyl at 180 will most likely not make a difference thickness wise in a smaller frame.

[Traci]

Given the popularity of small frames now, I chose the 1.6 aspheric. However, the frame size and the pd would have to be taken into account. I would do a lens thickness calc. to determine if it would be beneficial to use 1.6 or 1.67.

[Jedi]

Don't care what anyone tells you, use 167. Never use 166 you will end up eating 80% of them when the coating breaks down in 11 to 18 months.
Chip:finger:

Do you mean use 1.67 not 1.60 ?

[chip anderson]

Nope, (well sorta) While it may be the same stuff, I have used (to my regret) a lot of 166 (my spectacle patients are to a large degree, my contact lens patients and have a lot of high corrections). Most of the 166 has "coating failure" "that's the factory coating coming off, it can't be stripped or replaced" at about 11-13 months (usually just after the warranty runs out). Had the same trouble with cosmolite and stopped using it.

Now (I am told) the essillor (products that I have had excellent results with and for now, I "trust the company" is out in 167 and "won't have coating failure." Now either this product hasn't been out for a year or I have not been aware of and using it that long, so I don't actually personally know that the 167 will not deteriorate with time. For now, I am trusting, wishing and hoping. And yes I know the first rule about not trusting.

It is possible the my lab of choice was using an inferior lens mfg. for their 166 and cosmolite or the coating that failed was not "the factory coating". But I do know that I have had a great many patients that loved me because their glasses were so much thinner than previous glasses, that became disenchanted when their coatings failed. And I spent quite a bit of money making good on things that were just out of warranty. I have even seen the coatings on 166 fail as soon as 3 months. I have even seen Hoya's ultra-thin materials with ARC fail withing 4 months, so I am very reluctant to use this despite the profit potential.

[Pete Hanlin]

Regarding high index lenses and their coatings, I would say its going to come down to the individual manufacturer- not necessarily the particular substrate. There are only a few basic types of high index material, and they are- by and large- made by only two manufacturers (I believe they are Mitsubishi and Mitsui). Each lens manufacturer may add this or that to the material, but they're all about the same. Coincidentally, the same holds true for polycarbonate- GE and one other company (forget the name) supply pretty much all the polycarbonate used for ophthalmic lenses.

Anyway, if you have a coating that is failing to stay on the lenses- or is cracking- that is going to be a characteristic of that manufacturer's coating, not necessarily anything related to the material itself. A lot goes in to determining the "best" hard coating: adherence to the lens, tintability, strip-ability (for use in integrated coatings), flexibility, and even index (to reduce chromatic fringes). Each manufacturer determines their priority for each of these characteristics.

Essilor has a joint venture with Nikon, from which much of our high index technology springs. The coating we are using today on our high index lenses has evolved to provide the laboratory and the dispenser with more flexibility in processing these lenses for the end consumer.

As for polycarbonate and patient "non-adapts," I believe when an office (or chain) has trouble with poly- or any specific material- there needs to be an investigation behind the "real" causes of the difficulties. One of my departments is Market Quality, and on a manufacturer level, we just don't see a disproportionate number of polycarbonate lenses coming back for patient non-adapt.

[drk]

I surely appreciate everyone's input.
I am going to ask you to review what I'm doing and why. Please comment if you can help improve my approach, or point out any fallacies in my thinking.

(For low Rx's, we use spherical poly)

For moderately high minus patients (which I define as -3.00 sph eq. to about -6.00 sph eq.) I've been prescribing Optima's Resolution poly, due to the theories:
1.) Optima should know atoric optics pretty well, and atoricity is quite important
2.) Whatever the birefringence issue is, if it is one, this covers it
3.) The cost is good, which helps swallow AR and edge tx better
4.) This comes stock 1.2 mm CT, so no extra lab fee to center it at 1.0
5.) Abbe is no worse than the ultra high indices

For high minus patients (I define as -6.00 sph eq. and up) I've been prescribing 1.67 aspheric from Essilor:
1.) It offers significant thinning over the above option
2.) Yes, it's much more expensive
3.) No, it's not atoric.

In summary, we go:
Poly then fancy poly then ultrahigh index.

Thanks!

[Spexvet]

As for polycarbonate and patient "non-adapts," I believe when an office (or chain) has trouble with poly- or any specific material- there needs to be an investigation behind the "real" causes of the difficulties. One of my departments is Market Quality, and on a manufacturer level, we just don't see a disproportionate number of polycarbonate lenses coming back for patient non-adapt.

I agree, Pete. I sell tons of poly, and rarely have a patient with adaptation problems. I have contact lens wearers with -6.00 who want to keep glasses cost down. I'll sell them poly in a heartbeat.

In summary, we go:
Poly then fancy poly then ultrahigh index..

That's how I recommend. Of course there's CR-39 for those who insist. I very rarely sell mid (1.54/1.56) index or 1.6. I don't see a need and I don't find value in those materials - for me or my patient. I've sold about a dozen pairs of glass in the last seven years.

I used to use Hoya's 1.7, but not anymore - it looks gray and when viewing the sphere and cyl lines in the lensometer, they don't look crisp and sharp, to me. Has anyone else noticed this?

[drk]

Problem-solver materials:

CR-39 for cheapies

Glass for "generation PGX" , scratchers:angry:

Spectralite 1.54/ Trivex 1.52 for visual pickies.

Spexvet, I like you because you agree with me!

[Eddie G's]

I prefer to sell 1.74's over 1.67's.

[mrba]

blows me away that people would do poly in that and say it's best!

[drk]

MRBA:

Your opinion is valuable. Please elaborate as to what SPECIFICALLY you find is less optimal with polycarbonate. Is it regarding consistency of fabrication at the manufacturing or finishing level? Is it an optical quality? I realize the constringence value is low, but not necessarily much lower, on a percentage basis, than ultra high index, which is rather universally endorsed. Please reply, thanks.

[Jedi]

I prefer to sell 1.74's over 1.67's.

Eddie,
I've found in RX's under a -9.00 that there is not a significant difference in edge thickness between the two indexs. Have you run into that as well? Also in cases over that power I have more patients inclined to go with high index glass (1.8 or 1.9). In all honesty I have been dissappointed in the 1.74 index, what's your secret to success with it.

Jarratt

[Eddie G's]

Thanks for reminding me Jedi, I have to update my display of demo lenses in a -8.00sph. I need to add POLY, RESOLUTION and 1.74 in the comparison.
Is a -8.00sph a good power to compare all the lens materials?
Or should I use another power?

I'll post the edge thickness comparison's when I finish them.

GLASS lenses are avoided as much as possible in our practice.

I just sold the new Zeiss 1.74 to a previous Zeiss glass wearer (not sure if it was a 1.8 or 1.9) and he was very satisfied with that plastic lens. His RX was a -4.50.

Just saying to the customer that they are getting the THINNEST plastic lenses makes them feel better and gives me a peace of mind.
:cheers:

[sjthielen]

The seiko 1.67 has always been my favorite lens to wear and dispense. It provides great optics and is very thin and impact resistant.

[coda]

Coincidentally, the same holds true for polycarbonate- GE and one other company (forget the name) supply pretty much all the polycarbonate used for ophthalmic lenses.

Bayer is the other significant supplier of optical grade polycarbonate. Dow is making a play for the CD/DVD polycarbonate market so I expect to see them making in roads into ophthalmics.

[Rick Strong]

I went with 1.6 asph

The TL16 Crz is available in stock, quick service and a good lens.
If the money was there, 1.67 Crz would be offered as well.

my 2 cents