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Thread: Freeform +10.00 add 2.50 blended bifocal

  1. #1
    Join Date
    Jun 2006

    Freeform +10.00 add 2.50 blended bifocal

    I am new in freeform. IOT just installed
    Has a request of a job bifocal +10.00 add 2.50 blended on Poly

    At this moment i just have on stock single vision blank base 9.75 on poly. But the inside curve is arround -6.00.
    The center thickness of the blank is not enough.
    Also, the diameter of the blank is not enough. The digital blended is not being rotated by innovations or IOT.

    So advise is welcome.

    Also, where to buy thick high base single vision poly blanks.

  2. #2
    Doh! braheem24's Avatar
    Join Date
    Feb 2001
    KOCF & 89ft ASL
    Other Eyecare-Related Field
    You're going to need a 12 base for that lens and I've heard a lot of labs have not perfected the calibration on backside round segs.

    I would try x-cel for the thicker blank and base.

  3. #3
    One eye sees, the other feels. OptiBoard Gold Supporter
    Join Date
    Jul 2002
    Wauwatosa Wi
    Dispensing Optician
    X-Cel's spherical 1.55 comes in +10 bc extra thick and +10 and +12 standard thickness, specific values unknown.

    You'll need a steeper than normal (compared to front aspheric) base curve so the software has some curve, probably at least -2.00, to work in the needed asphericity. Poly, 1.67, and 1.74 is very dispersive at this power, especially with a multifocal. Avoid if possible.

    Ideally you want a front aspheric, but I don't believe most of the FF softwares can work with them, although Quest is making Essilor's Super Modular on a FF platform, but I wonder if then optimizations are limited to an atoric back surface.

    Note that Signet Armorlite has a 1.56 aspheric FT28 with a +9.75 (true curve unknown) that might work.

    Hoya may have steeper Trivex base curves. No details.

    CR39 should be on the table. In an optimal frame/lens/eye configuration it can be reasonably light in weight and not thick at the edges.
    Roberts Optical Ltd.
    Wauwatosa Wi.
    Science is a way of trying not to fool yourself. - Richard P. Feynman

    It is easier to fool a man, than to convince a man he has been fooled. -Mark Twain

  4. #4
    Bad address email on file
    Join Date
    Nov 2007
    Ft Lauderdale, Florida
    Other Optical Manufacturer or Vendor
    While not recommended for Optics, you may be able to make a biconvex blended. Its not ideal but someone with that power is also used to narrow visual fields. I would consider this option only as a last resort.

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