I have a pat. ,who is a pilot, needs basically a trifocal double seg. Does such a lense exist?
Thanks!
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I have a pat. ,who is a pilot, needs basically a trifocal double seg. Does such a lense exist?
Thanks!
It's called a quadrifocal, and the only one I se listed is by Vision Ease in glass.
Back in my school daze, I made a few quadrafocals, as they called em, where you basically had a double d where the bottom was a trifocal and the top was an upside down bifocal "D" seg. I've never seen a double trifocal. Doesn't mean they don't exist. Someone will be along to answer your Q. You might want to clarify exactly what you need.
If it can't be found, it could be made using the same technique as a Franklin bi.
Renegade!!!!Quote:
Originally Posted by Jacqui
:cheers:
There would be absolutely no use at all for a tri on the top and the bottom, period. Think about fitting, there would be no distance area to work with to make them work properly, maybe 5 mm for distance.:hammer: Bottom tri, top intermediate, deal with it.
It might be possible to have a FF lab surface a back side round seg onto the top of a trifocal, this would accomplish what you need and allow you to specify the add power int eh top segment as well as open up the material options. The power of FF.:cheers:
To add to this, just because we can, does not mean we should, ever. Hold true to what we do, and what we know.Quote:
Originally Posted by Jacqui
I got my last pair of blanks from them about 15 years ago. The upper add was the same power as the intermediate. To my knowledge there was never a plastic lens produced in this form but glass is superior in this use anyway.Quote:
Originally Posted by obxeyeguy
I have done occupational bifocal for pilots, but for the life of me I can't understand why he would need to read at 18" above his head, its usually intermediate only vision there because the top instrument panel usually sits at about 42"-58" inches.Quote:
Originally Posted by scriptfiller
You may check out Quest Optical Lab, they make a special pilot lens too, basically, if Quest doesn't make it, no one does.
http://www.questopticallab.com/pilots.html
Also, with a double tri, and counting the space between segments, I would need minimum a B measurement of about 51mm to make it work, I have not seen a frame that big in years. If you could do it in glass, it would weigh so much the guys face would be at his knees by the end of the day.
I have used standard double D's with much success..
Thanks for the responses. I looked-up the price for a Quad. from my lab.... the cost of the lense is more than what we billed the pat. for the entire order. I'll have to see if he wants to shell-out some serious bucks to do it. Also, the top segment would be a bifocal seg not a trifocal seg.
Thanks again for the responses and commentary, Optiboarders rock!
What kind of pilot is he exactly - and what type of A/C is he rated for again? I'd stay well out of his airspace from the sound of his lens wish alone! Yikes!
I'm willing to bet that a press on add would be a lot cheaper for the top portion.
One of my instructiors (3rd year I think) when I was in school for my license had a progressive with a press on add at the top. Because he could..... come to think of it, he was a little out there.....
What we do is serve our patients to the best of our ability with what we know. If it can be done, and the patient is willing to wait the time it takes, and pay the money it costs to make, then we absolutely should do it. Every time.Quote:
To add to this, just because we can, does not mean we should, ever. Hold true to what we do, and what we know.
Uilleann,
Flew in Vietnam. Former heavy equipment operator for NWA, retired due to age restrictions. CAP pilot and Cessna 172 owner. A personal acquaintance who I'd love to fly with again.
About the only reason he would need a top seg flying a C172 is to see the magnetic compass.Quote:
Originally Posted by scriptfiller
Yup. Don't need a trifocal for that.Quote:
Originally Posted by rbaker
And in *E-V-E-R-Y* C172 I've ever flown, and flown in (or 152, 182 etc.) none have had the compass over head. Something seems very wrong in his panel config! Yikes again! You could get him a pair of foggles, turn them upside down, and slap a stick on add to that. IFR all the time...yeah Baby! ;)
Last year I fit an ENT doc with a ff lens from 3R that mimicked the old Varilux Overview, which they discontinued about 10 years ago. I have been fitting this ENT doc with it for about 20 years now, it was a progressive, with an Ultex bifocal on top, developed, from what I remember, from NASA, to read all the instrument panels required in their space capsule. In any event, 3R was able to put a 45mm TK bifocal on top of a progressive to mimick the Overview. The doc loves it! Come to think of it, like one of the posters mentioned prior on this thread, through freeform. they could probalby put same bifocal on top of trifocal lens.
Uilleann,
He's left the 172 at his summer residence in Wisconsin, he is flying a different aircraft with a glass cockpit (don't know what it is) with the CAP here in Florida.