Innovations "Edge thickness on minus"

**gola** · 02-20-2006, 11:39 AM

Innovations has many features that i do not know jet and i am wondering if it can give the minimun edge thickness of a minus lens. On Innovations i can stablish the center thickness but minimun edge thickness will be determined by the prescription, type of lens, index of refraction, descentration, frame shape, etc.
Knowing the minimun edge thickness on minus prescriptions and where if will be, would help determine the apropiate center thickness specially on rimless frames.

Also, why not maximum edge thickness too.
This information would be valuable in some jobs.

**shanbaum** · 02-20-2006, 12:30 PM

I'm not sure what you're looking for. The minimum thickness parameters - edge, center, and average, all apply to all lenses regardless of power. If you were to set a minimum edge of, say, 5.0mm on a -2.00 prescription, the edge (at the thinnest point) would be 5.0mm or greater - that's what "minimum" means.

**drk** · 02-20-2006, 03:13 PM

We'd all like that, but what it would require to be effective would be frame shape information entered as well as patient pd and level MRP, and then you could theoretically "play" with the CT, index, lens design (as if you could accurately understand aspherics), and see what edge thicknesses result in the frame.

I would be willing to wager that wholesale labs can trace a frame, and figure out the edge thicknesses. But, you could probably do it "by hand" with a ruler: determine "h" in the maximum and minimum direction, then apply formulas from a self-programmable computer.

Sounds like a job for "Harry Chilenguarian".

In the future, it would be cool if we could all purchase such software, and get downloads from the frame manufacturers on the frame information for free! And I want a pony!

**rsandr** · 02-20-2006, 04:33 PM

Originally Posted by drk

In the future, it would be cool if we could all purchase such software, and get downloads from the frame manufacturers on the frame information for free! And I want a pony!

And it would be affordable, and I want the moon...on a stick.

**Darryl Meister** · 02-20-2006, 05:27 PM

Until then, this will get you pretty close: Lens Thickness Calculator. I do make some reasonable assumptions regarding the minimum thickness and Base curve (mostly based on the lens material) so that the ECP doesn't have to mess with the details.

**spartus** · 02-20-2006, 09:16 PM

Originally Posted by Darryl Meister

Until then, this will get you pretty close: Lens Thickness Calculator. I do make some reasonable assumptions regarding the minimum thickness and Base curve (mostly based on the lens material) so that the ECP doesn't have to mess with the details.

It is a great tool, and I use it quite a bit for reference. Thank you for supplying it!

However, since you mentioned it, it occurs to me that it'd be an even more interesting tool if you included an option for changing base curve--even just as a drop-down with 4 or 5 common bases. I know it's not exact, but it would be a useful thing to have access to.

**Darryl Meister** · 02-20-2006, 09:37 PM

Maybe I'll add that as an option over the weekend.

**spartus** · 02-21-2006, 01:10 AM

Cool. :D

**gola** · 02-21-2006, 07:15 AM

Originally Posted by shanbaum

I'm not sure what you're looking for. The minimum thickness parameters - edge, center, and average, all apply to all lenses regardless of power. If you were to set a minimum edge of, say, 5.0mm on a -2.00 prescription, the edge (at the thinnest point) would be 5.0mm or greater - that's what "minimum" means.

When calculating a job with a 3 piece frame (mounted with holes on the lens) you want a descent edge thickness where the hole are going to be drilled. Two exact lenses on the same frame shape, pd, etc but at different axis may require a different center thickness.
So knowing the minimun edge thickness is not enought. At what axis it is would help but stil better if i can know the edge thickness at any axis i choose.

In other words, i want to calculate the thinnest lens i can make but with appropiate thickness where the holes are going to be drilled.

I am shure that innovations has this information because it is needed to calculate minimun edge thickness but i do not know if it can be displayed.

Christmas wish. Show me the shape of the frame and the thickness the calculated lens would have wherever i point with the mouse.

**shanbaum** · 02-21-2006, 11:39 AM

OK, now I understand; you want to be able to specify a minimum thickness to apply at the drill features, and you'd like to be able to view the calculated lens thickness at any point on the lens.

**Darryl Meister** · 02-22-2006, 04:04 AM

Originally Posted by spartus

However, since you mentioned it, it occurs to me that it'd be an even more interesting tool if you included an option for changing base curve--even just as a drop-down with 4 or 5 common bases.

I've added an option to manually enter a Base curve in (from -4.00 D to +14.00 D). Click the button and a field will pop up. You can also use the button to see what Base curve was automatically computed for you by pressing the button to see the computed Base curve after calculating the thickness: Thickness Calculator.