Need help to calculate prism

[MIOPE]

I want to add to our in house software a module to calculate prism when the patient see away of the optical center.

One of the uses will be to help suspect diplopia if a bifocal or a progressive is prescribed. In this case I Would be interested in vertcal prism.

Correct me if I am wrong.
How to do it. Calculate the prescriptions power at the vertical axis. (90,270). On each lens.
Multiply this vertical power by the centimeters the patient is seeing away from the optical center. The difference in prism power will be what could cause diplopia.

Questions.
If patient is going to wear progressive or bifocals.
Which prescription is used for calcilatons? Far or near prescription?
How many milimeters the patient see away the optical center on a Flat-top 28 and on a progressive lens?

[Dr. Bill Stacy]

You use the distance powers, and it is the difference between the powers in the 90 degree meridian that you use to calculate the difference in prism that can cause vertical diplopia. The last question is determined by the fitting height and the segment height, and other factors like prism thinning.

[HarryChiling]

I want to add to our in house software a module to calculate prism when the patient see away of the optical center.

One of the uses will be to help suspect diplopia if a bifocal or a progressive is prescribed. In this case I Would be interested in vertcal prism.

Correct me if I am wrong.
How to do it. Calculate the prescriptions power at the vertical axis. (90,270). On each lens.
Multiply this vertical power by the centimeters the patient is seeing away from the optical center. The difference in prism power will be what could cause diplopia.

Questions.
If patient is going to wear progressive or bifocals.
Which prescription is used for calcilatons? Far or near prescription?
How many milimeters the patient see away the optical center on a Flat-top 28 and on a progressive lens?

I discussed the topic and a solution in a prior thread from some time ago, even provided an excel spreadsheet and solution for using differeing segs in PAL's, it's a controversial subject so I am putting on the flame proof underwear while sharing the link.

http://www.optiboard.com/forums/show...s-this-working