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Thread: Help please, How do you measure seg ht for blended bifocals?

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    Help please, How do you measure seg ht for blended bifocals?

    Hey everybody, got a question for you. Should I measure seg ht at the pupil or lower lid for a blended bifocal??? I thought they should be measured like a regular flat-top but now I'm not sure. Please help.
    Thanks!

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    Personally I measure it like a flat top. You do however have to take into account the width of the blend zone or the patient will be looking through it. A sola 22mm blended seg has a blend zone of 2mm. If you measured the seg ht at 12 at the lower eyelid, I would add the 2 back on to that and make the final seg ht 14. This way when the person lowers their gaze they will be looking in the clear part of the add and not the blend zone. This has worked well for me in the past.

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    Thanks so much for your help.

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    Any time I'm unsure of things like that, I like to use scotch tape and show the customer where the reading will be. Follow KStraker's advice, then apply scotch tape to occlude the area that the bifocal will be in. Then make sure that while looking straight ahead, the patient doesn't feel that the blended area will interfere with their distance vision. This helps me to reduce remakes and gives the customer realistic expectations.

    Good luck!

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    Master OptiBoarder Cindy K's Avatar
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    I'd be cautious of fitting these ANY higher than lower lid margin-- that two mm blend zone is mighty obvious to the wearer, and positioning this high will encroach on the distance.

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    The general rule of thumb in the old days when these were common was: measure like a flat top and add 2 or 3mm. I think it was 2mm. Come to think of it, we used to hold their old lenses in the frame up to the light against a solid background and use a sharpie to dot the top of the blur. It's a good idea to see where the old ones sit before measuring for the new ones. You wouldn't put someone in these that hasn't worn them before would you? The blur is supposed to be high which is why you add to the standard seg ht. The eye when looking downward misses it if you have done it correctly.
    Last edited by cocoisland58; 12-22-2006 at 08:24 AM.

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    Master OptiBoarder Cindy K's Avatar
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    Quote Originally Posted by cocoisland58 View Post
    Come to think of it, we used to hold their old lenses in the frame up to the light against a solid background and use a sharpie to dot the top of the blur. It's a good idea to see where the old ones sit before measuring for the new ones. You wouldn't put someone in these that hasn't worn them before would you? .
    Good practice to dot the top of the blur. Makes measuring much more accurate when matching a fitting height.

    Is there ANYONE using this old lens on new fittings? Its such a dinosaur! We have a few clients who've worn it for years (we do a couple pairs annually for these folks), all women if my memory serves me correctly, and all wear it for it's 'invisibleness'. Don't know if they realize it really isn't as 'invisible' as they think!

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    Master OptiBoarder ziggy's Avatar
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    Quote Originally Posted by Cindy K View Post
    Is there ANYONE using this old lens on new fittings? Its such a dinosaur! We have a few clients who've worn it for years (we do a couple pairs annually for these folks), all women if my memory serves me correctly, and all wear it for it's 'invisibleness'. Don't know if they realize it really isn't as 'invisible' as they think!
    I think I sell 4-6 pair a year also, also all ladies. World wide it must be used a lot, otherwise it would go the way of the exec. tri.
    Paul:cheers:

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    Never liked it...

    My opinion of the seg height was almost always misunderstood by the patient, then misinterpreted by the lab who often had their own ideas about how "they" needed to adjust your order. I prefer a standard round seg any day over a blended round seg. From a vanity standpoint you can barely see them anyhow and the seg ht. issue is not negotiable. If you really want to see something special, order from Three Rivers Optical their TR-O seg. Every pair I get in I look at them and go "wow thats nice":) Chris..

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