Splitting Prism BASICS

[John@OWDC]

Does anyone have a good, simple, "cheat-sheet" on splitting prism?

Please - nothing over-the-top technical or "look how smart I am stuff."

Just some basic, rule-of-thumb, concepts or guidelines.

I have someone sitting for a state practical and one of the questions may be about, "Splitting prism for best cosmetic effect."

Thanks,
John

[braheem24]

For cosmetic purposes,

Push BI on the most Minus
Push BO on the most plus
Push base down on the more plus PAL


None of it matters if their PD is 84 or their pupil placement is 5 Below.

[lensgrinder]

Does anyone have a good, simple, "cheat-sheet" on splitting prism?

Please - nothing over-the-top technical or "look how smart I am stuff."

Just some basic, rule-of-thumb, concepts or guidelines.

I have someone sitting for a state practical and one of the questions may be about, "Splitting prism for best cosmetic effect."

Thanks,
John

Hold your hands in front of each eye. When your hands travel in the same direction you will not be splitting the prism you will be cancelling. When your hands travel in opposite directions they will compound or add. For example 2.0 D BI OD, move your right hand in(toward the nose or to the left) 2.0 D BO OS, move your left hand out(toward the temple or to the left). Both hands travel in the same direction so this is cancelling(i.e. 2 D BI OD and 2 D BO OS will equal 0 D of total prism). Now take 5.0 D BI OD, split the number, 2.5 D BI OD and 2.5 D ?(what direction) OS. You moved your right hand to the right for BI what is opposite of right, left or BI. The direction of the left eye is BI(i.e. BI and BI will compound each other or add to each other)

[drk]

Do you mean:

Rx says:
OD plano, 2^ BI
OS -2.00 DS, 2^ BI

and you make it:
OD plano, 1^BI
OS -2.00 DS 3^BI?

[John@OWDC]

Thanks!

I will pass these along to her.

I appreciate it.

John

[braheem24]

Yes, if splitting is allowed and Patients is not borderline monocular OS.

Always take into consideration LCA induced wirh prism in dominant eye.

[Uncle Fester]

Do you mean:

Rx says:
OD plano, 2^ BI
OS -2.00 DS, 2^ BI

and you make it:
OD plano, 1^BI
OS -2.00 DS 3^BI?

This would produce best "cosmetic effect"???

[Robert Martellaro]

A better example would be...

OD -2.00 DS 4PD BO
OS -4.00 DS

Instead of an equal split, use...

OD -2.00 DS 3PD BO
OS -4.00 DS 1PD BO.

Consult the lab for exact details regarding edge thickness.

Another concern is with on-axis, prescribed prism induced lateral chromatism, and its associated reduction in visual acuity- use the least amount of prism in the eye that has the best acuity, or possibly the dominant eye.

[tmorse]

My guess is that a State practical exams would want to know only if the candidate knows how to split prisms equally for best cosmetic effect. So if the RX has one (1) eye with all the prescribed prism but the other eye has none, the Rule is…

AMOUNT: Cut total prism amount exactly in half, to make each eye the same amount of prism.
and
BASE DIRECTION:
a) If single eye prism was BI or BO, then make each eye this same BI or BO prism base direction
b) If single eye prism was BU or BD, then make that eye the same BU or BD, but give to the fellow eye an opposite base direction.

OD: -3.00 4.0^BI
OS: -3.25 ----

Split the prisms to
OD: -3.00 2.0^BI
OS: -3.25 2.0^BI


or,

OD: +2.50 3.0^BU
OS: +2.50 -----

Split the prisms to
OD: +2.50 1.5^BU
OS: +2.50 1.5^BD

[drk]

This would produce best "cosmetic effect"???

I don't know. Would it?

Should it be:
OD: plano, 3^BI
OS: -2.00, 1^BI
?

Ok, maybe that's better.

I mean, I WAS JUST TESTING YOU, FESTER!!!!!!

[Uncle Fester]

Me thinks Mr. Morse wins the kubie doll on this.

Now to hijack the thread and get technical--- Are yours and Braheem's answers the best technically using Robert's explanation?

Another concern is with on-axis, prescribed prism induced lateral chromatism, and its associated reduction in visual acuity- use the least amount of prism in the eye that has the best acuity, or possibly the dominant eye.

[optical24/7]

Does anyone have a good, simple, "cheat-sheet" on splitting prism?

Please - nothing over-the-top technical or "look how smart I am stuff."

Just some basic, rule-of-thumb, concepts or guidelines.


John

I pulled out my trusty Optics for Dummies book by Tarzan ABOC, I quote;

"Split prism same, inny nosey, outie eary, if one downy, other uppy cause Cheetah good monkey."


He goes on to say that the rule is easy to remember because "Cheetah IS good monkey."

[Dr. Bill Stacy]

Being more interested in the vision of the patient than how the glasses look, I tend to push more of the prism into the poorer seeing eye, or into the non dominant eye.

[Uncle Fester]

I pulled out my trusty Optics for Dummies book by Tarzan ABOC, I quote;

"Split prism same, inny nosey, outie eary, if one downy, other uppy cause Cheetah good monkey."


He goes on to say that the rule is easy to remember because "Cheetah IS good monkey."

TECHNICALLY--- Cheetah is not a monkey.

A poem to (hopefully) make you smile:

Cheetah flies through the air
Cheetah lose his underwear
Cheetah say me know care
Jane make me another pair

Boy flies through the air
Boy lose his underwear
Boy say me know care
Jane make me another pair

Tarzan flies through the air
Tarzan lose his underwear
Tarzan say me know care
Jane like me better bare!

[optical24/7]

TECHNICALLY--- Cheetah is not a monkey.

Funny you say that Fester. Tarzan ABOC actually has a disclaimer about that in the side notes;

" Me call Cheetah monkey cause me no spell Chimpanzee..."

[Robert Martellaro]

All of this jungle talk reminds me of a Far Side cartoon...

http://kittenita.blogspot.com/2010/1...nderstand.html

[John@OWDC]

tmorse

you da man!

well done

thanks
john