Does anyone know of any manufactures that make flatter stock lenses? We need a solution better than surfacing everything into a 4 base to fet these newer frames.
Thanks
-Billy
Does anyone know of any manufactures that make flatter stock lenses? We need a solution better than surfacing everything into a 4 base to fet these newer frames.
Thanks
-Billy
equal opportunity offender!!
Here's what I've learned...
For CR39:
- Pentax poly is great. They're a 2.0 CT for low minus powers which is great for grooving. They get thinner as you get higher. And their pricing on finished single vision hydrophobic AR is great for CR39, poly, 1.60 and 1.67. You wouldn't believe their power range for 1.67 finished single vision.
- AO Rugged Fashionwear is also great. They're a 1.2 CT across the minus range though, which is not great for grooving.
- Both of these brands are about a 3.50 to 4.00 base for plano spheres.
- Avoid Gentex poly and Vision-Ease Continua poly - both are way too curved.
- Essilor Airwear is also flat but a lot more expensive.
- We like the finished single vision lenses from www.superoptical.com. Again, very flat curves and very thin. They have both coated and uncoated and are located in Ohio just like yourself. Ground shipping would get them to you next day.
- Do not even bother trying Sola's Permagard or Silor's True Tint. They're terribly curved.
Hope that helps you!
-Steve
That's great stuff, Dr Snow. I use Somo poly stock for the same reasons. Flat curves, thicker at the low end, and less expensive than almost all others.
Polycore uses flatter curves as well. www.polycore.com
Delete.
Last edited by Metronome; 05-18-2009 at 02:14 AM. Reason: Delete.
Back in my day the criteria for base curve selection was the lens power. Has something changed? Is all of Dr. Tillyers and Zeiss's work no longer of value?
We've got an OGI frame (among many others) that had a 2-base demo lens in it. There's no way a 6-base low minus or low plus lens would work in there without either looking bad or popping out (my bigger concern). Most people don't have a really hard time adapting to changes like this though.
We set our lab software up to run flatter than average, such that pretty much everything that's less plus than a +1.25 gets run on a 4.00 or 4.50 BC for this reason.
We got a pair of uncuts in for another office (they were sent to us by mistake) from Custom Eyes in MN a few months ago. They were a -1.25 sphere OU and run on a 6-base. There's no way that would fit into today's flat curve frames without popping out at the top and bottom of the frame.
-Steve
Wow - those Somo lenses are nice and flat:
http://www.somoptical.com/pdfs/finished/POLYSPH.pdf
-Steve
Back in your days was also back in my days when you would give a low base curve to -4.00 and higher. Vision was more important than flatter and thinner for anything. This is not modern professional thinking but actually going backwards 90 years.
This is like being attracted only and to to look at flat chested women. Optics is not to promote flat..................but to promote best possible vision.
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Say what you want, but lenses popping out of frames ain't cool.
-Steve
I learned already a long time ago as an apprentice how to adjust the rim of a frame, either plastic or metal to the curve of the lens bevel, and sometimes even the bevel on heavy plus lenses, so that they would fit perfect. Of course this involved a little work on the hand stone and frame heater or pliers................and not from edger into frame as it is done these days.
And for sure we never saw any lenses popping out. So why replace good vision with not so good vision because of popping lenses. :finger:
Yeah, but why mess with potentially rolling a zyl frame or having to do that when you don't have to? I can't remember the last time I remade an Rx for a BC non-adapt.
-Steve
To be sure, an eight base in a thin rectangular titanium is a recipe for trouble. However, you can have your cake and eat it too- aspheric surfaces will allow the use of flatter curves without a compromise in optics.
However, we must warn the client that the vision off-axis will be compromised if you let the frame parameters drive the lens design selection, and don't or can't use aspheric designs when indicated. This will be a more of a concern with multifocals due to the increased time spent looking through the lens off-axis.
Good. That should keep the marginal astigmatism under .25 D for spheric surfaces at typical vertex distances, a reasonable compromise between fashion and function.We set our lab software up to run flatter than average, such that pretty much everything that's less plus than a +1.25 gets run on a 4.00 or 4.50 BC for this reason.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Great points Robert!!:cheers: I swear one day I'll have to head on up and buy you a drink!:D
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
I personally think you should start selling frames that are designed and manufactured properly, then you wouldn't have this problem. Doc Tillyer, Zeiss, et al. set the base curve system for a reason and that is better vision.
I think the frame mfgs would blame the lens mfgs. Flatter curves on lenses, higher indices, aspheric lenses; it forces then to make flatter frames It's a feedback loop, they (we) are all at fault.
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