Anyone design a 'ben franklin' lately?

[mbabc]

lurking mode off---

Esteemed fellow opticians,

(My first post on 'optiboard'...)

I have a local MD who specializes in muscle imbalance and had a patient with 4 D BO prism OU distance / with 7 D BI prism OU near. I (we) made "ben franklin" lenses. Take a look at the attached jpg, they worked great.

Has anyone experence with these before. My lab guru has only done a few in 30 years. None recently.

Mark M. Babcock
mbabc@home.com
web administrator; gosdok.com
'The Society of Dispensing Opticians of Kentucky'

lurking mode on---

[Joann Raytar]

Mark,

I am glad you turned your lurking mode off ... Nice Job! I have heard of those guys but have never seen one. Thanks for including the jpg. Did it take you awhile to run them?

[optigoddess]

I salute you & your lab guru ! How incredible....I've never seen such a unique thing....Hat's off...moment of silence from the Peanut Gallery PLEEZE......:D :cheers:

[kjw1231]

Hello,

There is a lab in Buffalo that will still produce a Ben Franklin. I am out of the business (still writing software for the industry), but seen one done a few years back. Can you say scoring and Canadian Balsm?

[chip anderson]

Have done this many times. The easiest/least expensive way to do this is: Have two pairs of SV lenses ground and cut full size for frame, one near one distance. Mark with a Pilot Ultra Fine point where to separate near and distance. Cut along line with a disc sander with a fence to near exact size. Finish doing the top edge of near and bottom edge of distance with a fine flat file til' a "perfect fit is obtained". If you feel the lenses must be cemented (I don't always) Edmund Scientific will have a proper adhesive.

This way you are only out time, and cost of two S-V lenses. And you don't pay a fortune and wait forever for speciallty labs to make it for you in a one-piece lens. Don't bother calling you lab to do this for you, they no longer know what a Franklin bifocal is. An even if you explain it to them the can't do with 2001 equipment what an optician could do with 1780 equipment. Strange huh?
:hammer:



Chip

[optyx]

Nice work on the Franklin.

I've only done two of these. The last one (I mean the LAST one)in 1990.

Having grown up there I'm glad to see "Luavull" represented on the Board.

[Darryl Meister]

By the way... This lens design is also one of the only fabrication methods available that allow you to incorporate significant amounts of horizontal prism at near only (i.e., independent of the distance zone). Other methods only allow relatively small amounts of horizontal prism at near -- that will often depend upon the add power. This kind of prism is sometimes prescribed for binocular vision anomalies associated with near vision and non-concomitant strabismus.

Best regards,
Darryl

[Clive Noble]

And I thought I was the last one left in the world who was fool enough to still tackle Franklin Bifos... Yes, I'm smiling.

I've done about 30 in the last 10 years, they all look pretty ugly, I do show the Pt a sample before I start however they do solve the problem of different prisms needed for distance and near and also different axes for D and N.

I do usually try to solve the problem using a wide seg bifo ST 45 and working contra prisms and decentering, see Jeff Trail's post on the general board, he describes how to do it very well.

As much as I dislike making Franklins, it's very satisfying to see how well it works.

If anyone needs a blow by blow account of how to do it....... email me

[chip anderson]

Clive:

If you doing a Ben Franlin, you use two single vision lenses split on the 180. You don' use any type of ST, round top, progessive or any other. Just two single-vision lenses split, Apearance should be almost like an executive. Adhesive may be used but event is not "purist" although it will keep it from getting dirt between the two half lenses.

Chip

Anything else is just not a "Franklin Bifocal."

[Clive Noble]

Hi Chip,

You're right. I use two single vision lenses which I cut out according to where I want to place the centres, relative to the patients eye when it is at the distance and near points in the frame.

I make sure the frame is either flexible enough (plastic) or preferably a metal frame, which means the work has to be more exacting (but as I'm a masochistic perfectionist that doesn't matter!)

The real work starts after the 2 lenses (for each eye) come off the edger. I than have to grind away the bottom of the distance lens, and the top of the near so the two can 'butt' together.

This is just 'hard grind' using a rough wheel, then smooth and finally fine wet'n dry sandpaper working with calipers for exact measurements.

The two components have to sit on each other without a gap and where possible with a continuous front base curve.

I've never yet used a glue to stick the components together.

One of the most difficult jobs tackled was a Franklin TRIFOCAL..... but after screwing around for a few hours, I realised that the Distance and Intermediate had the same degree of required prism, and it was only the near that was different, so I cheated and used an ST 35 seg Bifo as dist/intermediate.

Apart from the fact that they don't look too attractive, there are those patients who love them and for once can receive eye comfort in a bifocal

I actually enjoy the challenge of these sorts of jobs..... but then I am a masochist!!

[Larry W. Gray]

how did they cut the lenies to fit? I would like knowe.

[chip anderson]

Cut each S-V lens to fit and mount. Dismount and draw a line where you want the split to be. Cut 1-2 mm below line on upper lens and 1-2 mm above line on lower lens. Then trim to near line and finish with a very smooth large flat file. trial fit carefully as you work. Hold lens in hand and flile laying flat on a flat surface.

As I said earlier do your "cutting" with a disc sander with a fence. Practice on some old lenses first.

Chip

At least this will work fine on plastic lenses. For glass you have to grind very, very carefully, I would not do this on glass today, or at least not without a very good reason. Offhand I couldn't think of a good enough reason to do this in glass.

[Jerry Thornhill]

I had a similar Rx to about 10 years ago. We had to do 2 pair. One pair for eveyday wear and one pair of half eyes. Since it was before any hi-index material except poly we did it in regular plastic.

The half eyes were simple as they were a drill. Since the patient was plus and to keep thickness down ground a pair of ST-35 and made the top of the seg the top of the frame.

The regular pair of glasses made the distance Rx in single vision. Played with the Base curve so as to get a match for the back curve of the add. This was also made in single vision.

I did my part I gave it to Lou to make a 35mm seg out of these. After she had finished I then glued them onto the distance lens using a cement from Norland that was UV curable and had an index of 1.498.

Seemed to work well made two more pair of each for the lady before she passed away.

Jerry

[optixbil]

We do these for $100
Bill Belanger
Eyeris New England
800-443-4639

[Jimbob]

Hi all,
Surpriingly a lot of australian labs will do franklin fits for people, but it is always easier, and more satisfying to do the job for yourself...

Some forrm of bonding is always a good thing, helps you get away with not having a perfect fit, also makes fitting easier... think about it, you have to place two lenses inside one plastic frame forexample...not easy at all... at least with the glue its a regular fit..(more or less)

you just need to watch ourself with the vee bevel, as with an executive, it can be tricky to match these up with out moving the optical centre of the lens the wrong way, or creating unwanted prism.... once again bonded lenses!!

[chip anderson]

Why does everyone keep trying to make this so complicated and discussing the seg. size? Use single vision lenses for both halves of the lens. It's a lot less expensive, gives full field and is more optically correct. And you can have the centers, prism, and almost anything else, exactly where you want it/

Chip

[Jerry Thornhill]

Chip,
One reason is to make it look better and less noticable.

The one I did and made the segs would not have been a very appealing job any other way.

Distance correction +3.50
Add +3.00
Prism 6 Base IN OU

A single vision lens in CR with a power of +6.50 with 6 Diopters of Prism is not a very nice looking pair of glasses.

Jerry

[chip anderson]

Dar be a point whar you has to realize that glasses, specially de specialized type is to make people see. De cosmoletics is out de windo anyway. Every mm of lens should be dar ta see thru.

Chip

[Judy Canty]

Dar be a point whar you has to realize that glasses, specially de specialized type is to make people see. De cosmoletics is out de windo anyway. Every mm of lens should be dar ta see thru.

Chip

Really, Chip???

[chip anderson]

Really to me, perhaps not to others in today's world.

Chip

[Jacqui]

I agree with Chip :) :)

[Ory]

I agree with Chip :) :)

That's fine, but why did it take him 10 years to reply to the thread?? :)

[Jacqui]

That's fine, but why did it take him 10 years to reply to the thread?? :)

I was afraid to ask :D

[tdj]

Wait, so what exactly is the difference between a "Franklin" and "executive" bifocal?

[Speed]

Wait, so what exactly is the difference between a "Franklin" and "executive" bifocal?

$160