OD = Right eye
OS = Left eye
SPH = Sphere: It is the amount of long or short
sightedness correction required. The
value always has a (+) or (-) sign in front of it. There will always be a value
mentioned under SPH even if the value is 0 there will always be (SPH, PLANO or
a dash) written under it.
The power is measured is
dioptes.
CYL = Cylinder: It is the
amount of astigmatism correction required. For CYL also there will be (+) or
(-) sign in front of the value. It is not necessary to have a CYL value in a
prescription.
AXIS: This will only be
mentioned if there is a CYL value or astigmatism correction required. There
will be no (+) or (-) sign in front of the value and it is measured in degree.
The value ranges from 1 – 180 degree.
PRISM: Prism can be used to
correct vision of an individual whose eyes are not perfectly aligned. When the
eyes are not aligned properly the left and right eye sees differently as a
result the eye is not able to focus well and the vision is blurry or double
image is formed. In this case prism is prescribed on the lenses. Prism is also
measured in diopters and the symbol is a triangle (Δ). Along with prism value the
prism base is also defined and there are 4 different prism placements (base up,
base down, base in and base out)
If, you would need
prism correction we advice you fax the prescription or upload a scanned copy of
the prescription. There will be addition cost applicable for prism correction
and we will notify you once we receive the prescription.
PD = Pupillary distance: It is
the distance between the two pupils (Dark circle at the center of the eye) and
the measurements are in millimeters (mm). The PD is used to center the lenses on the
frames. The PD is mention in two
different ways Monoculer Pupil distance or Binocular Pupil distance. Monocular
PD is prescription if the pupils are not of same distance from the bridge of the
nose and it will be written as OD PD (Right eye) and OS PD (Left eye). The pd
for readers will be 2-5 mm shorter than Distance PD.
The average PD for an adult
will be from 58 to 70 and for children
it will be from 42 to 58
It is very important to provide
us with the correct PD for progressive and Bifocal lenses so that we can place
the lenses accurately.
Please copy and paste the link below on a new internet browser to know how to measure the PD.
http://www.opticstoreonline.com/pdfFiles/ruler.pdf
