Can you surface SV Poly Biconcave

[LENNY]

Hello everybody !!
I was wondering if you can surface poly biconcave with 3 BC
Do they make the blanks?
In general where do i find the info about semifinished products avialable and who is the most common manufacturer.??
Who is less expensive to buy from for my lab?
How do i find out?

[LENNY]

by the way the Rx is -15.00 ou

[Steve Machol]

Lenny,

By the way, you can now edit your own posts. You don't need to add a new message anymore.


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Steve
OptiBoard Administrator

[Jerry Thornhill]

Lenny,
I can see no reason why this can not be done. I do not do much Poly, but to the best of my knowledge a minus front curve is not available from the manufacturer.
I do not see a problem in doing your own curves. I have done this on plastic before a minus front was available. I have done 1.60 and and I have increased the minus curve on the front of Optima's 1.66. On the 1.66 I did a double myodisc and was able to do a -35.00 diopter sphere OU with a 28mm bowl. You can do most anything if you are willing to take the chance.
Jerry

[Matthew]

I know the place you can go, if they cant do it nobody can. Ask for Janet or JB. The place is Laramy K 1-800-525-1274 tell them Matt said to call.

[Jim G]

Not a problem, been doing 'em for 15 years. Before you surface both sides, check the .50 and 2.00 base lenses; the cc curve may be usable as your cx surface.

The pricing doesn't vary that much from manufacturer to manufacturer but the quality does. Would recommend making your decision on that at this point.

[Jeff Trail]

Lenny,

First their is no reason to use a "molded" concave lens design unless it is a multifocal. If it is a SV lens then all you need to do is use a standard lens blank.. flip it around and use the back curve as the "front" curve and grind the front surface of the lens..TADA a concave cut :-)
The only question I have is WHY would you want to do it on POLY for Gods sake? :-) Talk about adding hardship to an already "hard" case...
You would be better switching to a 1.60 index or even a 1.57.. I have cut a few of these over the years and find that if possibly try to stay around a -4.00 front curve...more then that and it tends to increase tunnel vision.
But if you have to have the info I'll post where it can be gotten in the morning when I get to my books at the office.. other then needing it in a hard seg design no need in paying xtra for a "molded" concave lens.
BTW any "lab rat" that's been around for a while will know this trick and if they do not? Well... you may want to try another lab. LOL

Jeff "Trix are fer kids..optics are fer NUTS" Trail