High Index Lens Becoming More Curved

[Barry Santini]

Confirm warpage by using lens clock and

check the vertical (90th) meridian. If the curve there is not as steep, the lenses are warping, for the reasons listed above.

Barry

[Andrew Weiss]

I agree with Harry C mostly. I'd just add that most jobs I see these days are made too large. If you use a polariscope on all your jobs for a week, you'll see what I mean. So I will bet that your lenses are stretching that frame. Correct sizing and matching the rear bevel to the frame bezel should do the job. And of course you'll need new lenses, although I'd suggest a 1.5 center instead of 2.0.

[hip chic]

Thanks for all of your replies. I'm sorry I didn't get back to you sooner about the frame style. I was away from my computer for a few days.

The frame is full metal stainless steel frame. The lenses are grooved to sit inside the frame.

hip chic

[Metronome]

The issue is mechanical, the frame bevel on a wrap is usually at an angle similar to the wrap angle. The bevel on the lens comes out of most edgers with the bevel and lens edge at 90 degrees to the front suface where it was blocked, over time a soft lens such as Poly, or a Eurathane (Hi-Index) will warp. The correct solution is not to cut smaller, or use thicker it's to relieve that pressure caused by the back ledge of the lens and the angle of the frames bevel. Multiple correct solutions:

1. Lenticular - There are lenses out there that can make the edge of the lens thin enough that the back ledge of the frame is not there to interact with the frame, these lenses come in both traditional and a blended lenticular.
2. Heavy Bevel - Hand edge the side of the lens that is causeing the issue to match the angle of the frame bevel, this will release the pressure and eliminate the issue.
3. Frame Modification - This could void the warranty so might suggest it as a last resort, modify the bevel of the frame so that the frames angle matches the lens angle, this could also be done with a bit of hand beveling where both lens and frame are modfied slightly as a hybrid solution.

DON'T - try to warp the lenses back into shape this is horrible suggestion, if you heat up hi index as suggested and place a weight on it you don't know what the outcome would be except warped lenses.

Delete.

[Fezz]

Welcome to the forum, Harry!

;):cheers::cheers::cheers::D

[tmorse]

We base curve match all of our jobs and in a thick frame like Chrome Hearts zyl, the heat will cause the lens to be overtaken by the frame curve. If you put them in a 6 base to start; all problems will vanish. Just remember to compensate for the curve and if you use the Autograph Attitude on a 6 base, you should have a job optically and cosmetically correct. It needs to be edged on a machine without wheels to ensure the curve/bevel are correct; this is essential on a 6 base thick zyl for cosmetics.

While not a 'lab tech', I believe you match a base curve to the RX and NOT to the frame. Do you truly understand the theory behind a corrected curve (best curve series) lens, Tscherlings & Oshwalt (sp?) ellipses, unwanted lens abberations, Vogel's formula for base curve selection? Darryl??

[FullCircle]

While not a 'lab tech', I believe you match a base curve to the RX and NOT to the frame. Do you truly understand the theory behind a corrected curve (best curve series) lens, Tscherlings & Oshwalt (sp?) ellipses, unwanted lens abberations, Vogel's formula for base curve selection? Darryl??

Barry Santini covered the whole base curve thing here: http://www.optiboard.com/forums/show...t=31241&page=2

The ability to change base curves for the frame is part of what makes the whole sunglass wrap lenses available to us. Now, putting a -3.00 -3.00 in a wrapped 8BC RayBan is much easier and ends with a every usable product for the patient.

[tmorse]

Barry Santini covered the whole base curve thing here: http://www.optiboard.com/forums/show...t=31241&page=2

The ability to change base curves for the frame is part of what makes the whole sunglass wrap lenses available to us. Now, putting a -3.00 -3.00 in a wrapped 8BC RayBan is much easier and ends with a every usable product for the patient.

I stand by what I have said. If you want good, useful optics throughout the lens you are just asking for peripheral trouble by using a +6.00 base curve on a -6.00 lens. Why would you lens surfacers sacrifice optics for cosmetics.... just because you can? Where's Darryl on this issue?

[snowmonster]

I stand by what I have said. If you want good, useful optics throughout the lens you are just asking for peripheral trouble by using a +6.00 base curve on a -6.00 lens. Why would you lens surfacers sacrifice optics for cosmetics.... just because you can? Where's Darryl on this issue?

I think this is sort of the difference between being "book smart" and "real world smart." There has to be a little give in the realm of optics, and in my experience, patients rarely complain of BC-related issues or symptoms. The fact is that an OGI 2-base frame won't look or fit great with an 8-base lens in it, so jobs get run flatter. The same is true for a wrapped frame with a minus Rx.

[tmorse]

I think this is sort of the difference between being "book smart" and "real world smart." There has to be a little give in the realm of optics, and in my experience, patients rarely complain of BC-related issues or symptoms. The fact is that an OGI 2-base frame won't look or fit great with an 8-base lens in it, so jobs get run flatter. The same is true for a wrapped frame with a minus Rx.

And I suppose you have of idea what an iseikonic lens is/does...

[snowmonster]

And I suppose you have of idea what an iseikonic lens is/does...

Yes, I do.

[tmorse]

I think this is sort of the difference between being "book smart" and "real world smart." There has to be a little give in the realm of optics, and in my experience, patients rarely complain of BC-related issues or symptoms. The fact is that an OGI 2-base frame won't look or fit great with an 8-base lens in it, so jobs get run flatter. The same is true for a wrapped frame with a minus Rx.

A relatively new frame design, wrapped frames are designed strickly for cosmetics by designers who have little or no inkling about optics. And I read that a lot of lab techs on this forum think that any base curve can be used anytime... this is hogwash.
ANSI standards for base curve must be within 0.75D of what optical lens engineers determine will give optimum vision. (I have no idea why our lens guru Darryl hasn't edified the lab tech masses(). Sure patients rarely complain, because they feel they were given imperfect vision by the Allmighty and, in any case, opticians very rarely order base curve, leaving such details to the labs. Surely they all know what they are doing. Ha!!:finger:

[HarryChiling]

A 1.67 fit at a vertex of 12.5mm in a -6.00 will have it's Ostwalt branch of the Tschernings Ellipse around a +7.00, vegels rule only applys somewhat to 1.49 so the wraps can work if done one higher indices, but tmorse is right the off axis power is a consideration and used to have a ANSI standard that required you check it so many degrees off axis in the 60's I believe. This is a guess but I would assume the reason for changing and removeing that standard was people did stick to corrected curve theory and all was well. If you're gonna go flatter or steeper than required use an aspheric that compensates for this change.

[HarryChiling]

ANSI standards for base curve must be within 0.75D of what optical lens engineers determine will give optimum vision.

Actually Ted ANSI standards dictate that the base curve must be within plus or minus 0.75D if a base curve is specified, so if the optician specified a horrible base curve then that's exactly what they'll get.

BTW, this isn't one of those labs guy's I keep the power on the correct curves except when isekonic lenses. In the case of cosmetics I use aspheric lenses so that I don't have to fudge the optics. Particularly like the SOLA ASL Spectralite great product.

[Craig]

You might want to try it before you knock it!!

A relatively new frame design, wrapped frames are designed strickly for cosmetics by designers who have little or no inkling about optics. And I read that a lot of lab techs on this forum think that any base curve can be used anytime... this is hogwash.
ANSI standards for base curve must be within 0.75D of what optical lens engineers determine will give optimum vision. (I have no idea why our lens guru Darryl hasn't edified the lab tech masses(). Sure patients rarely complain, because they feel they were given imperfect vision by the Allmighty and, in any case, opticians very rarely order base curve, leaving such details to the labs. Surely they all know what they are doing. Ha!!:finger:

I have been matching base curves and using the compensated RX for 100% of the work done over the past 3 years. This is done to ensure the client gets a frame that fits and feels the same as when the plano was tried on. They want the glasses to fit like a plano; not an 8 base frame with a 4 base lens or a 2 base frame with an 8 base lens that hurts their head.

The compensated optics are the only way to ensure the completed eyewear is what the client expected, not the optician expectations who doesn't utilize the technology of modern optics to build the best pair possible.

The new Maui Jim progressive and all the Shamir Attitude products work this way; pick the curve to match the frame and compensate the optics to match.

The result is a pair of glasses that the client loves and most opticians tell them won't work on that curve. The client does not even know what curve you are talking about.

Try it and you might change your mind: our number one lens used over the past 3 years is the Image 8 base in polarized poly. It was the only one available in the 8 base and we had great success with patient satisfaction and then optician satisfaction followed.

Craig
A guy who orders lenses for 3 stores in 8 bases for the past 3 years!