Massive Prism - any one brave?

[QDO1]

Any ideas?

-3.75 -1.75 x 10 23 base out 6 base up
-4.25 -1.00 x 10 21 base out 6 base down

Posible bif/multifocal next time too

Px has exhausted surgical options.

Clearly the lenses need to be a low chromatic distortion, Px last dispense was many years ago, had some form of glass in a hand made frame.

[LENNY]

Miodisc!?

Blended!?

Do they still make those?

[Clive Noble]

Here's one of our highest Rxs, from about 2 years ago.
The lenses were made by Laramy K after the Px had made many pairs around the world without success.


OD -26.00 /-2.00 x 83 9^BD and 18^BO
OS -24.75 sph 9^BU and 18^BO

She came in for an adjustment the other day still delighted with the vision.

I have to say, they are a bit thick even though we used 1.66 material

Good luck

[Cindy C.]

Oofdah

[jjx4js]

they still make the blended myodisc, I used one not to long ago.This patient was -22. or so,and they looked ok.Im not sure they are any better looking than a reg myo, but they are still around

[QDO1]

they still make the blended myodisc, I used one not to long ago.This patient was -22. or so,and they looked ok.Im not sure they are any better looking than a reg myo, but they are still around

yep they still make myodiscs... are they anygood for prism though?

[chip anderson]

They are O.K. if you don't mind the patient seeing through the blend. Mean I don't think it will work.

Chip

[rsandr]

Any ideas?

-3.75 -1.75 x 10 23 base out 6 base up
-4.25 -1.00 x 10 21 base out 6 base down

Posible bif/multifocal next time too

Px has exhausted surgical options.

Clearly the lenses need to be a low chromatic distortion, Px last dispense was many years ago, had some form of glass in a hand made frame.

Try Lentoid in Leeds.
Im sure Jack Jones will relish making these lenses,

Rick

[QDO1]

Try Lentoid in Leeds.
Im sure Jack Jones will relish making these lenses,

Rick

I will call them up, shall I tell them who refered me?

[spartus]

Pech Optical did one of these for me about a year ago:

OD: -7.75 -3.75 10 BU
OS: -4.75 -3.50 10 BD

It was a FT28, can't remember what material it was--1.56 or 1.60 if memory serves, but it wasn't as awesomely terrible as you would think.

[Jim Stone]

Please let me know how you come out. I have been grinding lenses for thirty + years. I am quite sure there is a definate point you reach of prism it becomes impossible to grind. I think you may have one here. Press on may by your only answer. The high prism Clive mentoined in the thread with those super high minus lenses was probably easer to gring due to the high power than your weaker rx lenses. The movement of the optical center would creat effects of prism in large amounts with little movement. Surely blended myodisc is NOT the answer in this situation. They are only for higher minus lenses. You may talk to the guys at epic, they can grind some things that are realy tough. Please let me know what you resolve.

[Bev Heishman]

We do Rx's like this all the time. The best index is CR-39. The dispersion involved in the prism alone countered by a lower abbe like 1.6, 1.58 is an instant rerefract if the dispenser doesn't know how to trial frame. CR-39 and glass have the same ABBE. The highest in prism in a frame we have done is 9 base up and out with 9 base down & out. Keep the frame small with the decentration within 2-3mm distance & vertical.

[Jim Stone]

We do Rx's like this all the time. The best index is CR-39. The dispersion involved in the prism alone countered by a lower abbe like 1.6, 1.58 is an instant rerefract if the dispenser doesn't know how to trial frame. CR-39 and glass have the same ABBE. The highest in prism in a frame we have done is 9 base up and out with 9 base down & out. Keep the frame small with the decentration within 2-3mm distance & vertical.

I am sorry Bev. You have ground a total of 9 diopters. QD01 is asking for a ground prism of about 24 diopters. I don't think you can wind up with a reasonable product in lenses this weak. If anyone has , let me know. PLEASE! :hammer:

[Bev Heishman]

I am sorry Bev. You have ground a total of 9 diopters. QD01 is asking for a ground prism of about 24 diopters. I don't think you can wind up with a reasonable product in lenses this weak. If anyone has , let me know. PLEASE! :hammer:

Sorry Jim, I didn't see the 23 diopters with the 6 out until tonight. :hammer: :D Why isn't this person a candidate for surgery?

[QDO1]

:D Why isn't this person a candidate for surgery?

The patient allready had major surgery. 6th Cranial nerve damaged in car accident. On consulting Dr. was told that further surgery may only partially allieviate problem, but could cause many other problems. On balance Px and Dr decided to leave it allone

[Fezz]

I may be out of line, but.....What about Fresnel Press-on prism? I know most will say that they are only temporary. I have many patients who have worn theses for years. The awkward look of the Fresnel may be a better option then the thickness of the lens with the ground in prism. Good luck.



Fezz
:cheers:

[QDO1]

I may be out of line, but.....What about Fresnel Press-on prism? I know most will say that they are only temporary. I have many patients who have worn theses for years. The awkward look of the Fresnel may be a better option then the thickness of the lens with the ground in prism. Good luck.



Fezz
:cheers:

We thought that too. The patients VA is excelent, and the fresnel does work, but drops the patient 4 lines down the chart

[Bev Heishman]

We have had some pretty tough cases like this. We refer for other another opinion. Did this patient have a second opinion? If yes then I beleive the Fresnel is the only option. The blank thickness alone is a barrier. The trade off of 4 lines may be better than trying to keep this Rx in place.

[QDO1]

The trade off of 4 lines may be better than trying to keep this Rx in place.

Well the challenge is more interesting - as the chap allready has a pair of spectacles that is about 7 years old with slightly more prism in. Unfortunatally the fella that surfaced them isnt alive any more, and the company he worked for havent an idea how to repeat the job

[QDO1]

Well well well. Seems the Brits have come up trumps.. Lentioid in Leeds certainly surprised me, by sending some fine mock up blanks, with the full prescription surfaced on it, in 1 day from calling them... Yes I said surfaced. 100 Brownie points to Jack @ Lentiod in Leeds UK

:drop:

That was:

-3.75 -1.75 x 10 23 base out 6 base up
-4.25 -1.00 x 10 21 base out 6 base down


We see the patient tomorow and only have the folowing hurdles to get past

- Eye exam
- Measurements
- Getting a hand made frame
- Glazing
- Adaption
- Any other problems

Easy then
To be fair to the US, LaramyK said they can surface the lenses too, and apparantley they did a higher script last year, but I would imagine there was a higher Sph/Cyl script

[optispares]

hope we can improve on the job with some different blanks for the finished article.

[Jim Stone]

Well well well. Seems the Brits have come up trumps.. Lentioid in Leeds certainly surprised me, by sending some fine mock up blanks, with the full prescription surfaced on it, in 1 day from calling them... Yes I said surfaced. 100 Brownie points to Jack @ Lentiod in Leeds UK

:drop:

That was:

-3.75 -1.75 x 10 23 base out 6 base up
-4.25 -1.00 x 10 21 base out 6 base down


We see the patient tomorow and only have the folowing hurdles to get past

- Eye exam
- Measurements
- Getting a hand made frame
- Glazing
- Adaption
- Any other problems

Easy then
To be fair to the US, LaramyK said they can surface the lenses too, and apparantley they did a higher script last year, but I would imagine there was a higher Sph/Cyl script

I'd love to see. Can you scan a photo from different angles. I have many questions. I'd like to know the frame size and material used. Also how much tollerance used (if you have equipment to check them out)? You can email if you like. Please let me know these things.

[QDO1]

I'd love to see. Can you scan a photo from different angles. I have many questions. I'd like to know the frame size and material used. Also how much tollerance used (if you have equipment to check them out)? You can email if you like. Please let me know these things.

Well we are a long way off from finishing the job. As I havent paid Jack @ Lentoid for them (these were only mock up lenses), we would have to ask Jack (aka. OPTISPARES) if he is prepared for people to view his genius bit of surfacing

The frame will probrably be hand made

The surfacing tecnique isnt for me to divulge!

The prism and power was pretty spot on! after we checked it using a rotary prism, a couple of lenses from the trial set and the extreeme of the screen

[optispares]

:o

we would have to ask Jack (aka. OPTISPARES) if he is prepared for people to view his genius bit of surfacing

.
not really genius just a matter of conning a coburn xrt into generating a bit of extra prism by changing the prism index . i.e.the lenses are cr39 1.5 index so by entering a prism index of 1.250 and generating 10 prism you get 20 prism in the
lens.

[shanbaum]

:o .
not really genius just a matter of conning a coburn xrt into generating a bit of extra prism by changing the prism index . i.e.the lenses are cr39 1.5 index so by entering a prism index of 1.250 and generating 10 prism you get 20 prism in the
lens.

You're under arrest.