Are there any progressive lenses available that have a horizontal prism incorporated into the NV portion only?
I have a patient with double vision at near only that is alleviated with total of 3 Base-In prism OU but cannot tolerate prism for DV.
Thank you in advance for your comments.
There are no progressives that I know of that do this. The only way to really accomplish what you need is with a Franklin bifocal.
You would probably be looking at big bucks, really big bucks, to fabricate a one time use mold. And GOK what the addition of prism would do to the optics of the lens. Forget it. Send the patient to a good optician for a Franklin bifocal or trifocal.
I was told there was one by Kodak, but all the information is in a file at my work. On Monday, I'll get it out and let you know the name of it.
It's nice to be important, but it's more important to be nice.
I have used the computer/magnifier flip-ups and put in lenses with prism to wear when reading....... Not many other choices ...... reading glasses ..... close one eye when spot/short-term reading ???
Homer
You can also use flat-tops, depending on the power, and decenter.Originally Posted by Jacqui
Try a Fresnel press-on prism, cut it for the near portion only ?
It would take a fairly high correction to do it and then you probably wouldn't have a lot of useable read area. Franklins are going to be the best way to go. It's going to take a real optician to do it right.
Not sure about the "real" optician comment, but let me take a shot at this. A FT 45 with a +2.50 add would need to be decented 6mm in each eye to induce 1.5 BI. Add in the normal inset of 2 for a total of 8.5 in each eye to obtain 3.0BI total, as OP said. We started with a 45mm, with a center point of 22.5, decented 8.5, still leaves at least a 28 mm usable seg area, depending on frame size and actual PD.
All done for 1/5th the cost, and also by a real optician.
Better recalculate, he wants 3 BI on each eye
OK, I see 3 total. Da# MD's!alleviated with total of 3 Base-In prism OU
Cute idea :D
I apologize for not being clearer. We need a total of 6 Base-in prism divided as 3 BI OD and 3 BI OS only for near. No prism for distance.
I appreciate your responses.
Even a 45 won't really give him enough to use properly. An Exec, maybe, if the frame is small enough. A Franklin is the best answer.
:cheers:
At 3 BI ou, I tend to agree. I will say that with a +2.50 add it is still possible with a FT45, and the net reading area is almost as large as the progressive the OP wanted to prescribe.:cheers:
They only use .50 base in. Period.
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
You're right. It was later after re-reading the original post that I realized the OP needed way more prism. It hit me about the .50 BI as soon as I read that. Thanks for knowing what I was thinking, though!! :)
It's nice to be important, but it's more important to be nice.
Single vision readers is what I usually recommend. The PALs can be used for distance, some intermediate (dash panel for instance), and maybe occasional glances at the near point. Computer use would probably require special design multifocals, i.e. Franklins, prism segs, etc., or when it must be an all-in-one solution.
Epic has similar products.
http://www.epiclabsinc.com/
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
All of this depends on the distance Rx; if minus, you're cooked. If plus, 3 BI might be achievable with little enough seg inset to leave a usable field. I've used obx's trick successfully more than once.
Myopes get BI prism induced when converging, hyperopes BO. For example, a +5.00 distance lens with the eye converging 2mm induces 1^ BO. Although the Rx is for 3^ BI near only, the effective prism with the distance Rx in situ would be 2^ BI. I assume the prism power for near was determined over the distance/near Rx, so this is all probably moot.
However, SV readers using the near PD won't have prism induced from the distance Rx. This lack of induced prism should be accounted for, making sure that the prism at near is in line with the prescriber's original intent.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
From the way the question was asked, I thought the Dr. was talking about an all-in-one.
This is the same kind of work that I do, I just don't brag about it as much and I don't have a fancy website.
:cheers:
This patient will have no prism in the distance, because the correct PD will have been used. To get prism in the near only, unusual seg inset (not just decentration) will be used. If this patient is ou -2.50 with a +2.50 add, insetting/decentering 50 yards will produce zero prism. If +2.50 ou with a +2.50 add, then insetting an extra 6mm ou will give the desired 6^ total BI desired. A finished PD for this patient might be 65/50.
Good thinking, but the problem in this situation is it sounds as though this patient cannot converge much at all (hence 6BI at near)!
I would go for a franklin type solution or multiple pairs. I have one little girl right now that has both accomodative insufficiency and converge insufficiency (orthophoria at distance) that I Rx'd a general purpose PAL for and separate SVNear with prism for reading.
Forget all these expensive band aide lens concoctions and cure the patient with vision therapy. 6^ of convergence would not be that difficult to take care off with good optometric vision therapy.
I don't know why it has been so hard for ophthalmologists to admit VT really works. Probably because it is in the domain of optometrists and does not pay them thousands of dollars like cutting a perfectly good muscle does. Sorry, I digress. The CITT study did have a positive effect though. Some strab surgeons I work with are actually starting to catch on.
In all honesty I think vision therapy is the patient's best option.
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