Lens Thickness Guidelines........

[Mrmessi]

I wanted to make a guideline for the store i work at for the different indexes and powers.

Full Frame Plastic And Metal

Index Power

1.49 0.00 to -2.25
1.56 -2.50 to -3.75
1.60 -4.00 to -6.50
1.67 -6.75 to -8.50
1.74 Over -8.50

Semi-Rimless Frames

1.49 0.00 to -2.50
1.56 -2.75 to -3.75
1.60 -4.00 to -5.75
1.67 -6.00 to -6.50 ------> Not advisable

I also know that other factors need to be taken into consideration such as lens shape, size and pd measurements.

Is there anything that anyone would change?????

[OpticianVlad]

You are not going to recommend any poly lenses? index 1.589???

[Mrmessi]

You are not going to recommend any poly lenses? index 1.589???

We only do poly for rimless and minus quarter sph/cyl thats about it, sometimes SV high index polarized lenses also because other indexes don't tint as well.

If anything i would put the poly in the range of 1.6, correct me if i'm wrong anyone.

[uncut]

Looks like good guidelines to me.....I would suggest adding aspherics to the mix. I often rethink whether to use aspherics in a certain job. Availability doesn't mean it is necessary. or necessarily a good thing.

[DragonLensmanWV]

I would suggest dropping the 1.56, except for Transitions FT-28, since that's about the highest index in FT Trans. The 1.56 is just too brittle. Whatever you do, don't use it in rimless, grooved or otherwise. You also need to add Trivex in there for all your drill mounts.
Aspherics are also good,provided your frame PD and customer's PD aren't too different.

[Mrmessi]

I would suggest dropping the 1.56, except for Transitions FT-28, since that's about the highest index in FT Trans. The 1.56 is just too brittle. Whatever you do, don't use it in rimless, grooved or otherwise. You also need to add Trivex in there for all your drill mounts.
Aspherics are also good,provided your frame PD and customer's PD aren't too different.

What about 1.6 index for grooving?????

[braheem24]

1.6 comes in 2 version both good for drilling and grooving, The MR-8 version has better abbe and is better for drilling and grooving as opposed to the MR-6.

[Bill Mahnke]

You might consider 1.70 as an alternative (in some cases) to 1.74 index

1.70 has a higher abbe, 36 compared to 33 with 1.74
1.70 is lighter weight, sg of 1.41 compared to 1.47 for 1.74 index (did you know that 1.74 is the heaviest plastic material used in the industry?)
1.7 works for drill mounts, 1.74 is not so good since it's brittle

1.70 has an index of 1.70 and 1.74 has an index of 1.73, so sure 1.74 would be a bit thinner in most cases. Some labs will surface 1.70 to a "1.0" center, while most labs will only surface 1.74 to a "1.5" center. The benefit of a lighter weight, optically better material that's not as brittle, may prove to be a better choice than 1.74 in many cases.

As said earlier you really need to have Trivex on your list for most 4D or lower prescriptions.

[HarryChiling]

I've always grouped materials.

Basic:

CR-39
(1.498)
1.32 g/cm³
Abbe 56.8

Power Range (+2.00 to -2.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Crown Glass
(1.523)
2.54 g/cm³
Abbe 58.6

Power Range (+2.00 to -2.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Mid Index:

Trivex
(1.53*)
1.11 g/cm³
Abbe 45

Power Range (+5.00 to -4.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Spectralite
(1.54)
1.21 g/cm³
Abbe 47

Power Range (+5.00 to -4.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Polycarbonate
(1.589)
1.20 g/cm³
Abbe 30

Power Range (+3.00 to -5.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Hi Index:

Finalite
(1.60)
1.22 g/cm³
Abbe 42

Power Range (+6.00 to -8.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

MR-10
(1.67)
1.36 g/cm³
Abbe 32

Power Range (+6.00 to -10.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Super Hi Index:

Teslalid
(1.71)
1.41 g/cm³
Abbe 36

Power Range (+8.00 to -14.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

MR-174
(1.74)
1.47 g/cm³
Abbe 33

Power Range (+8.00 to -14.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

I like to pick the material group based on the patients Rx, then the specific material based upon the patients work, activities, and hobbies. More active lifestyles go into more impact resistant materials. The patients that are sensitive to prescription changes go into optically clear materials.

[Mrmessi]

I've always grouped materials.

Basic:

CR-39
(1.498)
1.32 g/cm³
Abbe 56.8

Power Range (+2.00 to -2.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Crown Glass
(1.523)
2.54 g/cm³
Abbe 58.6

Power Range (+2.00 to -2.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Mid Index:

Trivex
(1.53*)
1.11 g/cm³
Abbe 45

Power Range (+5.00 to -4.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Spectralite
(1.54)
1.21 g/cm³
Abbe 47

Power Range (+5.00 to -4.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Polycarbonate
(1.589)
1.20 g/cm³
Abbe 30

Power Range (+3.00 to -5.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Hi Index:

Finalite
(1.60)
1.22 g/cm³
Abbe 42

Power Range (+6.00 to -8.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

MR-10
(1.67)
1.36 g/cm³
Abbe 32

Power Range (+6.00 to -10.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

Super Hi Index:

Teslalid
(1.71)
1.41 g/cm³
Abbe 36

Power Range (+8.00 to -14.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

MR-174
(1.74)
1.47 g/cm³
Abbe 33

Power Range (+8.00 to -14.00)

Weight
Chemical Resistance
Impact Resistance
Optical Clarity

I like to pick the material group based on the patients Rx, then the specific material based upon the patients work, activities, and hobbies. More active lifestyles go into more impact resistant materials. The patients that are sensitive to prescription changes go into optically clear materials.

Thanks it looks good to me. These days everyone is going for the bigger retro frames which is bad for the optics side because anything bigger will increase in weight and thickness.

[oxmoon]

Thank you Harry for posting your chart. I didn't know how badly I needed it until I saw it.

[oxmoon]

One question. Script for script your chart makes it look like 1.67 will weight less than 1.74. Am I reading this right?

[essegn]

One question. Script for script your chart makes it look like 1.67 will weight less than 1.74. Am I reading this right?

In general, it is natural that the higger the index is, the more weight has material itself. But in result, for the same power 1,74 will have less thickness as 1,67 because it "bends" the passing light more. For these two materials you will notice it from power +-5 and more (not near plano power).

Density for 1.74 - 1.47 g/cm³
Density for 1.67 - 1.35 g/cm³