This is something that bothered me off and on since I started as an optician, but I'm finally going to ask it why are two different symbols used for diopters.
What I mean is for Sphere and Cylinder wrote independent of a full RX all I ever seen used is D (or DS and DC for sphere and cylinder respectively)
But for prism all I've seen used is Δ.
Why the difference?
My opinion is as follows:
1) Ophthalmic optics requires uniformity for calculation so D is the short for diopters and applies in formulas and calculations, d is for distance.
2) Clinical optics which encompass charting, notations on records, refraction information divulged, and general discussion can be a meld of the usual formalities, but involve regional and corporate slang references, such a dio, dptr, ds, etc.
Eyes wide open
I always figured the triangle was used for prism because a prism is like a pyramid which is a triangle. Uncut answered the other questions
yes, we never used P.D. for prism diopters because that would be confused with pupillary distance; so the triangle became standard, which it should not because the triangle is also mathematical for "change" or "difference" Since the triangle requires a bit of computer savvy to use, I just use the carat ^ for prism diopters, knowing that's also wrong because it means mathimatically an exponent follows.
No symbols for diopters, just abbreviations.Originally Posted by jpways
D is an abbreviation for diopter, DS is for diopter sphere, which is used to designate the spherical component of the Rx when there is cylinder, where DC is for diopter cylinder, the cylinder power.What I mean is for Sphere and Cylinder wrote independent of a full RX all I ever seen used is D (or DS and DC for sphere and cylinder respectively)
DS is also used used on a Rx to designate the lack of cylinder. Sometimes written as Sphere, or shortened to SPH in the cylinder column of the Rx, or sometimes just a dash, the idea being that if left blank, it could be an error of omission, where some designation makes it clear that there is no cylinder, now way no how.
Yes, the delta symbol, used to designate prism diopter. MD's sometimes abbreviate with PD, not to be confused with the optician's pupillary distance, or more correctly, IPD, the Interpupillary Distance.But for prism all I've seen used is Δ.
A prism diopter is unit of deviation of the light ray (1cm at 1M), where a diopter is a unit of power, or focal length (1/M).Why the difference?
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.
The Δ symbol is sometimes also used in place of the word "change," as in "RX Δ". Be wary.
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I've never seen that, but I have seen axes written with a degree sign, for example 15°.
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.
I've seen the delta symbol being used on a few RXs to signal that there was a Rx change....not many and haven't seen one in a few years
Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity
Saw it back in the 90s, didn't see it for years, and then the doctor I currently work for uses it. A blast from the past for me.
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If I received an Rx like that I'd call the prescriber and then tell them to cut it out.
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.
When making quick notes to myself I use the triangle to mean "change" which is commonly used that way in science and math, but since I also use it to mean "prism diopters" when writing a spectacle Rx. This always is at the end of the distance Rx lines, following the sph-cyl powers, and always preceded with a numeric value for the prism amount and followed by a base direction.
When hand written I use the Greek Delta triangle, but when typed into my system I use the carat so it ends up looking like this
+1.00 - .25 x 90 2.5^ base up & 1.5^ base in
-.0.50 -2.00 x 3 1.0^ base down
add 1.50 OU
So as in most languages, you have to understand the context to know the meaning.
This is particularly challenging to us opticians when the change is in the prism. ;-)
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Prism is afocal doesn't effect focal power Power (Sph and Cyl) are measured as inverse focal powers so the Greek delta is used to differentiate. The Greek delta is also used in mathematics to designate change or the differential x2 - x1 = delta x it's shorthand. We should never use delta to designate change, the same thing applies to the degree symbol on an axis it should never be used as it could be misinterpreted as a 0 so an 18 could be read as a 180. DS and DC are also recommended as good form to provide clarity, at a point in time it was common for astigmatic patients to get a script of -2.00 × 180 which sometimes would be interpreted as -2.00 sph instead of Plano -2.00 × 180. For definitive answers for accepted standards look to the International Council of Ophthalmologist which dates back to the 1800's
If I write Δ Rx add +.50 O.U. it is unmistakeable what I mean. I could write "Change Rx, add half a diopter of plus to both lenses", but that would cramp my fingers by the end of the day.
It is the accepted practice in the medical field to always write a new Rx. By convention, it is unacceptable to "alter" or "modify" an existing Rx.
of course. I use shorthand in clinical notes made during patient encounters, partly to save time and energy, partly to obscure what I'm writing from patient/family members prying eyes...
That said, it's common practice to use well understood abbreviations in Rx writing. Less so now with electronic writing, where abbs. are less needed/appropriate.
As long as your shorthand isn't appearing on your instructions to the optician for the lens change.
I'm Andrew Hamm and I approve this message.
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