High index single vision lenses

[12345]

Hi, is there any difference in vision when compared to essilor's crizal 1.67, zeiss clarity AS 1.67, hoya's 1.67 nulux as well as a standard 1.67 hmc lens. I do know that the multicoat applied to the lenses are different, but is there any difference in the vision seen by the px? Another qn will be is zeiss individual a single or double aspheric lens design?

[drk]

In reality, I think not.

[essegn]

All of them use their's own asphericity, so it could be a slighty difference among them. In this case i would no say that any of them is better than others (for particular lens power maybe). Probably the best way is to wear them all and compare :)
To lens material itself should be the same (mr7 or mr10) and all AR coatings have light transmission near to 99.9%.

Individual lenses have sense only when the pantoscopic tilt and wrap angle differ from average.

The using of single or double aspheric i would like to know as well.

[Darryl Meister]

Since it is optically optimized for the position of wear as well as the prescription requirements of the wearer, Individual Single Vision utilizes a "complex" surface on the back of the lens. Unlike simpler, symmetrical aspheric and atoric surfaces, the asphericity of Individual varies on a point-by-point basis over the lens.

There is no need for "double asphericity," since the design is also optically optimized for any cylinder power in addition to the sphere power before it is fabricated onto the back of the lens blank using a free-form generator.

In terms of design sophistication and potential visual benefit, you can think of it as follows:

1. Spherical design
2. Aspheric design
3. Atoric design
4. Complex free-form design

If the patient has no cylinder power, and selects a frame that has relatively little pantoscopic tilt and wrap, an aspheric design will often suffice. But keep in mind that even semi-finished aspheric designs still rely on base compromises, so many prescription powers will not achieve optimal visual performance.

Once significant cylinder power is incoporated into the prescription, an atoric design or better is required to achieve optimal vision. But, again, base curve compromises are often involved.

Once any frame tilt or prescribed prism is considered, a complex free-form design like Individual SV is required to achieve optimal vision. And these lenses do not suffer from base curve compromises either.

As for whether the patient will notice the difference, it will depend upon the patient's sensitivity to blur, the nature of the viewing tasks involved, and the deviation of the patient's prescription and position of wear from the values utilized to design traditional (semi-finished and finished) spherical, aspheric, and atoric lenses.

Best regards,
Darryl

[Java99]

I wear these lenses, and dispensed about 50 of them from various manufacturers last year. The higher the power, the more people cared. The -2.00 sph wearer never commented much. The -4.00 -1.25 @ 135 wearer was "wowed." The high wrap rx sunglass wearer was wowed as well.

[Darryl Meister]

The higher the power, the more people cared

Yes, a good point to make. You can assume that the optical errors produced (and, therefore, potentially eliminated) will be proportional to lens power.

Best regards,
Darryl

[Barry Santini]

But, the -2.00 client wearing "flattened" poly stk lenses, fitted at mechanical center, in a frame where there is little pantoscopic angle and the pupil is 6-9mm above MC WILL MOST DEFINITELY see a difference when remade in FFSV with a 42-59 ABBE material, and with the base curve matched to the frame-bevel's curve.

B

[Darryl Meister]

The saddest part about this whole discussion is the fact that most eyeglass consumers have absolutely no idea that such factors exist or that an optician who understands optics is essential to making the most informed decisions that result in the best lens. Most consumers just seem to learn whether Lens A is cheaper than Lens B.

Best regards,
Darryl

[EyeCare Rich]

Totally agree with Darryl here. All we can do at this point is try to keep plugging away with our communication to the patients we do see, and hope they tell their friends as well.

Love the comment by Java99 above. Love that WOW factor, or the initial "my vision is to clear" comment when the patient follows your recomendation to go freeform, either SV or Progressive.

Keep spreading the word folks! Don't forget to ask your patient to spread the word as well.

[Java99]

But, the -2.00 client wearing "flattened" poly stk lenses, fitted at mechanical center, in a frame where there is little pantoscopic angle and the pupil is 6-9mm above MC WILL MOST DEFINITELY see a difference when remade in FFSV with a 42-59 ABBE material, and with the base curve matched to the frame-bevel's curve.

B

Absolutely. I didn't think about it because I can't recall the last time I didn't take an OC on someone.

[MakeOptics]

I think the design element is lost in this discussion, even the same manufacturing technique for achieving best form will not result in the same lens viewed through the patients eye's. As mentioned their are a lot of variables when creating the most optimal lens, but their are also different philosophys as what constitutes the best lens design. Even in SV lenses only so many aberrations can be corrected at one time, so the design has to weigh which aberrations to correct for more than others and balance the scales if I may. Each manufacturer will have their own set of weights and scales so the visual outcome will be different.

If you don't believe me try putting a patient in 3 pairs:

1) OU - Essilor 360 SV
2) OU - Zeiss Individual SV
3) OD - Essilor 360 SV; OS - Zeiss Individual SV

I would suspect that the patient will be thrilled with both 1 and 2 (my preference would still be towards 2 though), and even be able to regularly switch between 1 and 2 with praises for both, but option 3 would be a horrible failure. I have found this is also the case with aspheric stock lenses, I don't mix between manufacturers.

[12345]

in terms of off axis performance regarding the following four options that are essilor's crizal 1.67, zeiss clarity AS 1.67, hoya's 1.67 nulux as well as a standard 1.67 hmc lens, is there going to be any difference? im guessing yes if each of the companies uses different mathematical calculations for their lenses right?

[RKJ]

I agree with you that we don't intentionally mix brands between the right and the left eye. Having said that, I would not expect the Essilor 360 to be clinically equivalent to the Zeiss Individual. I think the Essilor 360 is Free Form, meaning the topography is unique to each Rx and is mathematically calculated to decrease the aberrations of 1.Oblique Astigmatism, 2.Power Error, 3.Spherical Aberration, 4.Coma, and 5.Distortion. Both brands would do this. The Individual would go a step further as it can be customized for vertex, panto, and tilt. The other way the lenses will be different, I think, is their default values for the position of wear measures. Zeiss publishes their default values. I have not seen Essilor publish their default values. If we had them, we could predict when the lenses would be similar in optics.

Essentially, all Free Form lens designers are using the same optical equations we learned in school to minimize the same aberrations. I imagine the industry would agree regarding those aberrations with greatest impact on visual clarity. In the identical index of refraction, I'd expect clinically equivalent lenses to be pretty much the same. I have not experienced an argument otherwise for Single Vision Lenses. I understand the design argument for Free Form progressives, that the progressive blend zone can be customized in a proprietary way, but I don't understand design differences for Free Form Single Vision Lenses. I'd like other opinions about this, with optical arguments.

Free Form lenses have a different topography nasally than temporally, and the topography at the top of the lens will be different than the bottom of the lens. Topography varies with angle between the eye and the lens and the distance between the eye and the lens. Provided all of the same data, I would expect clinically equivalent Single Vison lenses (those that analyze the same parameters, and that are equally customizeable for vertex, panto, and wrap) to have very similar optics.

The additional advantage is computerized measuring techniques. Some manufacturers are using new technologies to obtain better auto-refractions, sometimes better than the patient's ability to select a best quality subjective refraction - or perhaps better than the refractionist's ability to get a best quality subjective from the patient. These leaders in our field are gathering lots and lots of data, fine tuning their automated measures against subjective refractions. When they improve their technology until is succeeds the majority of the time, I think we'll see patients gain access to online refractions with their online eye wear orders, bypassing the doctor visit. Time will tell.

I'd sure like to hear the thoughts of others on this topic.

[Barry Santini]

Absolutely. I didn't think about it because I can't recall the last time I didn't take an OC on someone.

Your post made me think of an excellent Q for the ABOM exam:

How would one ensure a BF/CC compliance in a bifoal/trifocal fitting?

B

[Craig]

But, the -2.00 client wearing "flattened" poly stk lenses, fitted at mechanical center, in a frame where there is little pantoscopic angle and the pupil is 6-9mm above MC WILL MOST DEFINITELY see a difference when remade in FFSV with a 42-59 ABBE material, and with the base curve matched to the frame-bevel's curve.

B

Mr. B.,
Please keep the bevel stuff on the down low. People are listening.
Craig

Do you take a ht on all orders? We did but, the plus lenses started coming in too thick so we went back to the old lazy way. I can do it on all but high plus as the still don't use aspheric blanks yet for the ones who need it.
Your thoughts.