Is this too thick?

[oxmoon]

After listening to all the praises for Zeiss GT2 3D 1.74 I ordered a pair. It took 5 weeks to get them and the minute I put them on I knew they were exceptional, as in WOW. They are replacing Physio 360 in 1.67 in a Kawasaki 3 piece drill mount But they are much thicker than i thought they would be, and of course heavier too. Much thicker than the physio, and the only change was upping the add from 2.50 to 2.75, and very slight change in axis. The right lens ET is 6.1mm and left is 5.8. Rx is OD +50 -5.75 X 96, OS +.25 -5.50 X 92. I am already loving them except for the thickness issue and don't want to send them back, but will do so if it could be done again and come out thinner. Am I expecting too much? I was using myself as a guinea pig and thought I could interest l alot of patients in this lens because this is a fairly high end shop, but our patients are not the sort to stand still for paying alot and not getting just what they want in the cosmetics. Thanks very much for any advice.

Ox

[AngeHamm]

After listening to all the praises for Zeiss GT2 3D 1.74 I ordered a pair. It took 5 weeks to get them and the minute I put them on I knew they were exceptional, as in WOW. They are replacing Physio 360 in 1.67 in a Kawasaki 3 piece drill mount But they are much thicker than i thought they would be, and of course heavier too. Much thicker than the physio, and the only change was upping the add from 2.50 to 2.75, and very slight change in axis. The right lens ET is 6.1mm and left is 5.8. Rx is OD +50 -5.75 X 96, OS +.25 -5.50 X 92. I am already loving them except for the thickness issue and don't want to send them back, but will do so if it could be done again and come out thinner. Am I expecting too much? I was using myself as a guinea pig and thought I could interest l alot of patients in this lens because this is a fairly high end shop, but our patients are not the sort to stand still for paying alot and not getting just what they want in the cosmetics. Thanks very much for any advice.

Ox

What's the CT on each of them? If it's thicker than 1.5 in the new ones you're completely justified in asking for them to be remade.

[scriptfiller]

Got your cyl at the 180, make sure the CT is no thicker than 1.8 and check your frame shape/size with respect to decentration. Too much decentration can kill a good looking lense.

[oxmoon]

CT is 1.9 and right lens has decentration which explains why its thicker with roughly equal script bilaterally. But don't want to send them back without knowing they will come out better next time. I thought the Zeiss lab in Germany would be the premier lab and not create much that wasn't just right. When they got to the Zeiss lab in California I got a call that they had come in pretty thick and they offered to do a remake there in 1.67. I shoulda taken them up on that offer I guess, but was yearning for 1.74 now that I'm somewhat in the know. I appreciate your advice.

[jefe]

Between the Zeiss lab in Germany and Northeast Lens, I had an order a few years ago which took a half year to get okay. It was a +4 sph OU in a 1.6 or 1.67, and it kept coming back with a 4mm edge. They must have done it six times.

[uncut]

@o.p. is the thickness at the upper(temporal) edge greater than the lower?

[oxmoon]

What does @o.p. mean?

[DragonLensmanWV]

Original Poster.

[oxmoon]

@o.p. is the thickness at the upper(temporal) edge greater than the lower?

No, thickness is significantly less at the upper temporal edge, flaring out as the 180 is approached and remaining to the bottom of the lens. What would greater thickness at the upper edge mean??

[WFruit]

Somebody get Darryl in here. However, without his expertise with the Zeiss lenses, I'm going to ask about prism thinning between the two pairs. Also, is there any difference in seg ht between the two pairs of lenses (not what it should be, but what it actually is.)

And, as has been mentioned before, most Free Form lenses optimize for optics first, cosmetics second.

[uncut]

No, thickness is significantly less at the upper temporal edge, flaring out as the 180 is approached and remaining to the bottom of the lens. What would greater thickness at the upper edge mean??

The amount of prism thinning......thus creating a presence or absence of cosmetic emphasis. As WFruit pointed out, often optics overrides cosmetic concerns. Perhaps the effective radius is also creating extra thickness.

[DragonLensmanWV]

That's a lot of cyl at vertical axis, your temporal side should be sorta thick. But we don't know the size of the frame, nor the decentration. Dimensions, please?

[oxmoon]

That's a lot of cyl at vertical axis, your temporal side should be sorta thick. But we don't know the size of the frame, nor the decentration. Dimensions, please?

The lenses are made from Kawasaki EB41 blanks and in Kawasaki 631 three piece drill with size 19 bridge. All very small. Seg height is right on. Don't kknow about measuring prism thinning, that is still over my head and nobody around to ask.

[WFruit]

[Picky lab rant]The lenses are cut to the Kawasaki EB41 shape, not made from Kawasaki EB41 blanks.[/Picky lab rant]

We need the A, B, ED and DBL of the glasses. We already have your Rx, but we also need your PD and the seg ht.

In my view, a CT of 1.9 is too thick to begin with, though I can see where the slight plus power can affect that.

[Robert Martellaro]

Ox, could you be specific with your statement "Much thicker than the physio?" A 1mm difference might be perceived as quite a bit thicker in a full rimless frame, especially if you were counting on a thinner lens. So, compare the minimum thickness (the thinnest part of each lens), prism thinning, if any, the base curve of each pair, and note the edge design. Did Zeiss have an accurate tracing?

I suspect the Essilor lens might be a tad flatter (bi-aspheric) which would be good for a couple of tenths thinner. 1.74 might need to be a little thicker to pass impact resistance tests- .4mm or so thicker. However, the index of refraction will reduce the maximum thickness by about 9%, about .5mm thinner. In other words, a wash.

For now, my money is on a larger value for minimum thickness, and differences in prism thinning with the Zeiss lens.

[Uilleann]

Was the Physio lens cut to the same pattern exactly, as well as identical layout measurements? What was the change in axis exactly? You said the power overall didn't change in the dist Rx - not even a quarter here or there?

[PaulX608]

Since these lenses are plus power in the 90 combined with the +2.75 add, the thinnest place should be the bottom edge. Prism thinning would balance the thickness of the top and bottom, but if the CT is 1.9, the bottom edge must not be much more than 1.4, which I guess would be the minimum you'd want. Or is my week off affecting my geometry?

[oxmoon]

ET of the Physios is R 4.1 and L 4.0. Zeiss lenses were "cut to" (thanks uncut) the exact same blanks. Sunclip bought for the Physios will not fit on the Zeiss because of the thickness. PD is 52.5 (R 25.5 L 27) Physio ET is R 4.1 and L 4.0. Top edge of Zeiss is R 1.7, bottom is 1.9 and L 1.6 and 2.0. No change in sph whatsoever (big change was 3 years ago from -2 to what it is now after not having an exam for 7 years!). Axis change was OD 87 to 92 and OS 95 to 96. I would like to answer all your questions but am not that knowledgeable, having no formal training at all, and very little OJT since I started here last summer. I am trying to educate myself, but there are still many gaps. And aside from the thickness, I absolutely love the Zeiss lenses.

[oxmoon]

ET of the Physios is R 4.1 and L 4.0. Zeiss lenses were "cut to" (thanks uncut) the exact same blanks. Sunclip bought for the Physios will not fit on the Zeiss because of the thickness. PD is 52.5 (R 25.5 L 27) Physio ET is R 4.1 and L 4.0. Top edge of Zeiss is R 1.7, bottom is 1.9 and L 1.6 and 2.0. No change in sph whatsoever (big change was 3 years ago from -2 to what it is now after not having an exam for 7 years!). Axis change was OD 87 to 92 and OS 95 to 96. I would like to answer all your questions but am not that knowledgeable, having no formal training at all, and very little OJT since I started here last summer. I am trying to educate myself, but there are still many gaps. And aside from the thickness, I absolutely love the Zeiss lenses.

Post wrong info. Axis OD from 95 to 96, OS from 87 to 92

[uncut]

oxmoon: A few vital bits of info needed to express an opinion.......A, or lens size dimension. B, or vertical lens dimension. Seg height, or location of MRP will suffice.

Thanks,
uncut

[oxmoon]

oxmoon: A few vital bits of info needed to express an opinion.......A, or lens size dimension. B, or vertical lens dimension. Seg height, or location of MRP will suffice.

Thanks,
uncut

Lens size 41, vertical dimension 27, seg 19.

[Robert Martellaro]

ET of the Physios is R 4.1 and L 4.0.

You're saying the max thickness for the Zeiss lens is 2.0mm more in the right, and 1.8mm in the left, same shape, size, edge, and identical vertical and horizontal fitting distances (the Rx cahnge is inconsequential)? I don't see how this could be due to surface design alone. Locate the prism reference point (use the manufactuerer's template if you wish) and measure the horizontal OC value for all four lenses. While your there, note any base up or base down prism.

PD is 52.5 (R 25.5 L 27)

Red flag. That's typically what I see for a five to ten year old. Confirm.

[oxmoon]

You're saying the max thickness for the Zeiss lens is 2.0mm more in the right, and 1.8mm in the left, same shape, size, edge, and identical vertical and horizontal fitting distances (the Rx cahnge is inconsequential)? I don't see how this could be due to surface design alone. Locate the prism reference point (use the manufactuerer's template if you wish) and measure the horizontal OC value for all four lenses. While your there, note any base up or base down prism.

Red flag. That's typically what I see for a five to ten year old. Confirm.

That was worth a good laugh. PD is correct, but I am slightly over the age of 10, The two pair are identical in every way except for the slight script change you have discounted. But the 1.74 Zeiss is that much thicker than the 1.67 Varilux . Whatever it is due to, I don't understand why Zeiss would make them that way. And I probably won't send them back because I love them more everyday and can't stand the thought of going back to the Physios for 2 more months.

[uncut]

IMO....The thickness change is due to prism thinning, combined with the increase in add power. The actual thinnest point on this RX is the top edges of the lenses, due to the greater plus power at the bottom of the lens and the longer corridor length with the Zeiss product. The prism thinning instituted will have created an upwards shift in the geometric distance oc creating a thicker bottom outer edge, and subsequently an thinner top temporal edge to the lens. I think the lab was reluctant to create an even thinner top edge to the lenses, a consequence of reducing the overall lens thickness. They also were probably reluctant to surface the distance oc higher which would have reduced the bottom edge(outer) and increased the upper(temporal) edge.

[beagleman]

Oxmoon, if your frame is 41-19, FPD = 60, total decentration of 8mm total. I would imagine that much decentration is what is most of the problem.