Next generation Progressive design?

**braheem24** · 10-30-2009, 11:12 PM

Improvements have been made with progessive designs in the past few years with freeform and backside adds.

My question;
Why has no one combined 2 indices (indexes if you're an optician) in a PAL design?

Using 2 seperate different indexes, the higher in the add area will require less blending because higher indexes require less curves to achieve the same output, so with the new 1.70 and 1.74 index lenses would it not be an easy undertaking?

**Chris Ryser** · 10-31-2009, 02:43 AM

Originally Posted by braheem24

Using 2 seperate different indexes, the higher in the add area will require less blending because higher indexes require less curves to achieve the same output, so with the new 1.70 and 1.74 index lenses would it not be an easy undertaking?

.....................and would bring you right back into the age of fused bifocals.

**Jacqui** · 10-31-2009, 09:26 AM

Sounds easy :D Just glue them together like I do Franklin bi's .:D

**Darryl Meister** · 10-31-2009, 10:41 AM

would bring you right back into the age of fused bifocals.

Which, of course, were not progressive lenses. ;)

Why has no one combined 2 indices (indexes if you're an optician) in a PAL

In order to maintain a smooth change in addition power with no visible discontinuities, you would have to produce a material with a carefully controlled gradient refractive index of much of the lens blank.

And keep in mind that rear prescription curves would also be influenced by the refractive index, unless you are using some sort of composite or laminated lens. Otherwise, any gain in front surface power would be offset by a gain in back surface power, particularly in minus prescriptions, without the use of unusual surface geometries.

You could do all of this in theory, but it wouldn't be particularly practical, nice looking, or cheap.

**braheem24** · 10-31-2009, 11:41 AM

about 15 years ago sola had a system of laminating 2 lenses to produce an rx with a/r on both sides called matrix (I mention this system cause I'm sure you know the capabilities and limitations) can this process not be used to produce a gradient multifocal much like a prism ballast?

**Darryl Meister** · 10-31-2009, 11:44 AM

Yes, a lamination system like Matrix could be used, but all of the limitations that I described earlier would still apply.

**FVCCHRIS** · 10-31-2009, 07:34 PM

I love it when you guys talk dirty!....:bbg:

**AWTECH** · 11-02-2009, 01:11 PM

Originally Posted by braheem24

Improvements have been made with progessive designs in the past few years with freeform and backside adds.

My question;
Why has no one combined 2 indices (indexes if you're an optician) in a PAL design?

Using 2 seperate different indexes, the higher in the add area will require less blending because higher indexes require less curves to achieve the same output, so with the new 1.70 and 1.74 index lenses would it not be an easy undertaking?

Technically this maybe possible with blending of indexes and design considerations, however the greatest problem as I see it is "Cost vs Benefit". The blanks would be very expensive, my guess is 4 to 10 times the cost of a single index blank and the benefit would be marginal in 90%+ of the cases.

**DragonLensmanWV** · 11-02-2009, 01:44 PM

The AtLast lens is made from two different indices, just not maybe the way you're thinking.

**Darryl Meister** · 11-02-2009, 01:57 PM

The atLast lens achieves a discrete change in add power by laminating two lenses together with different refractive indices, which is essentially the same way that a fused glass bifocal works.

**drk** · 11-02-2009, 02:53 PM

My guess: the future of progressives is cheap cheap cheap moldeds that will compete quite nicely with digitals.

Word for the wise.

Look for deflation to hit progressives.

**Mr. Finney** · 11-02-2009, 02:54 PM

Wouldn't taking two lenses of differing indeces and laminating them together introduce all sorts of abberations?

"You could do all of this in theory, but it wouldn't be particularly practical, nice looking, or cheap."

I was looking at the website for atLast! just this morning, and they claim it to be as thin as 1.74. Hard to believe since 1.74 is aspheric and the composite is aspheric trivex and 1.67.

**dwbport** · 11-02-2009, 03:33 PM

Originally Posted by Mr. Finney

Wouldn't taking two lenses of differing indeces and laminating them together introduce all sorts of abberations?

"You could do all of this in theory, but it wouldn't be particularly practical, nice looking, or cheap."

I was looking at the website for atLast! just this morning, and they claim it to be as thin as 1.74. Hard to believe since 1.74 is aspheric and the composite is aspheric trivex and 1.67.

AtLast lens isn't as thin as any of other lens that I have...:finger: Thought I'd try it before marketing it to our pts. but:hammer: I just can't get over that blur since I'm a PAL wearer...... maybe when I'm reallllly old!! Also it's heavier.

**Darryl Meister** · 11-02-2009, 04:47 PM

I was looking at the website for atLast! just this morning, and they claim it to be as thin as 1.74. Hard to believe since 1.74 is aspheric and the composite is aspheric trivex and 1.67

Keep in mind that the atLast lens does not produce a progressive change in addition power using two different materials. Two materials are used to produce the addition power though the round segment.

**JerryR** · 11-02-2009, 05:54 PM

The add power on the Atlast lens does not come from the different indices used, but comes from a power bubble on the front surface of the back part section that is infused with the front section. Similar to two wafers infused together. Hope that makes sense.

**Mr. Finney** · 11-02-2009, 06:01 PM

Originally Posted by JerryR

The add power on the Atlast lens does not come from the different indices used, but comes from a power bubble on the front surface of the back part section that is infused with the front section. Similar to two wafers infused together. Hope that makes sense.

So it's a blended seg fused to a smart seg? I don't get it. What exactly do they mean by "power gradient", which I'm assuming is on the front of the front part, since the segment is "embedded".

**Darryl Meister** · 11-02-2009, 06:58 PM

The add power on the Atlast lens does not come from the different indices used, but comes from a power bubble on the front surface of the back part section that is infused with the front section.

The round segment (or "power bubble" as you call it) provides an add power because there is a difference in refractive index between the Trivex (1.53) front wafer and the high-index (1.67) back wafer. This is the same in principle to a fused bifocal.

The remaining addition power is produced by a low-powered progressive surface molded on the front wafer.

So it's a blended seg fused to a smart seg?

Both SmartSeg and atLast combine a lined bifocal with low-powered progressive optics for intermediate utility. However, SmartSeg contained the progressive optics within the flat-top segment molded on the front surface.

The progressive optics and the round seg are separate in the atLast lens. Also, the progressive optics span the lower half of the lens; the optics are not confined to the segment area. This results in some differences in optical performance as well.