Description
This article is from the Vision and Eye
Care FAQ, by grants@research.canon.com.au (Grant Sayer) with
numerous contributions by others.
2.1 How to read a glasses prescription
A prescription for spectacles will generally contain the powers for lenses
of each eye, possibly also a reading addition power, information on the
separation of the lenses and any special requirements for the lenses (eg,
type of lens, tinting, coatings etc). Lens power is written in Dioptres,
which is 1/focallength(metres). For example, a 5.0D (5.0 dioptre) lens
has a focal length of 0.2m or 200mm
An example of a spectacle correction is -
Patient Name <Person F Bar>
OD: +1.50/-1.00 x 35
OS: +1.75/-1.25 x 135
Add: +1.50
PD 62
The terms mean
OD - oculus dextrum or right eye
OS - oculus sinistrum or left eye
Add - Near addition
PD - interpupillary distance
The prescription values are read, firstly for the right eye
+1.50 - spherical power (positive)
-1.00 x 35 - cylindrical lens of negative power with axis at 35 degrees
Note: There may be variations in the way that the prescription is written
since there are different standards for the way cylinders are
represented and the coordinate system of the axes.
The coordinate system for the prescription is 0 to 180 degrees with 90 at
the vertical or 12 o'clock position.
RIGHT EYE LEFT EYE
90 90
| |
135 | 45 135 | 45
\ | / \ | /
\ | / \ | /
\ | / \ | /
\|/ \|/
180 ======+====== 0 < NOSE > 180 ======+====== 0
Other WWW references:
URL: http://www.west.net/~eyecare/optical_lens_prescriptions.html
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health, vision, eye care, contact lenses, spectacles, eyecare, prescriptions, sunglasses, surgery
