question about eyeglasses' cylindrical, cylinder + and - ? the same?!
Question: Question about eyeglasses' cylindrical, cylinder + and - ? the same?
according to that site,
"Some optometrists may represent a cylindrical number in the (+) range (traditional method of representation), while some may represent them in the (-) range. In any case, they mean the same. "
so are they the same? true or false?
Answers:
It means the same...yes and no.
Even if I call a lab and give them the Rx in the + version , they will transpose it to minus before making the lenses. The whole industry works in the - CYL form except the Ophthalmologists. That is just the way they have been taught to do the refraction , which isn't better or worse...just different, but with the same result.
An example prescription written by an ophthalmologist is :
- 1.50 SPH + 0.50 CYL X 90 AXIS
In order to fabricate that Rx it will be changed to :
- 1.00 SPH - 0.50 CYL X 180 AXIS
The prescription is the same .
BUT...If the Rx is supposed to be - 1.00 - 0.50 X 180 , but is ordered as - 1.00 + 0.50 X 180...the Rx will be wrong....because then it will become - 0.50 - 0.50 X 90
So, they are the same...as long as they are transposed right before making them.
Optician
The CYL power means the same but what is around may change if you convert from + to -. Glasses are only made with - power. All the eye care team uses the - power except for ophthalmologist which use plus.
+ CYL prescription:
+2.00 +2.00 x180
-CYL prescription:
+4.00 -2.00 x90.
Good luck
Eye care specialist.