Understanding your glasses prescription
OD og OS
CYL is an abbreviation for cylinder, which tells you whether or not you have astigmatism in one or both of your eyes. If there isn’t a number then this means you do not have astigmatism. The larger the number, the greater the astigmatism.
It may sound slightly serious to find out that you have astigmatism in one of your eyes. But this simply means that there is a slight imperfection in the curvature of the cornea. Astigmatisms are corrected by the lenses of the glasses.
If you have astigmatism, the direction of the curvature will be indicated using the term Axe. This will tell you which direction the defect is in. This is measured in degrees. The number given indicates the severity of the astigmatism. The number is between 0-180, where 90 corresponds to the vertical meridian and 180 is the horizontal meridian. This number tells the angle that is required for the lenses to be in order to take correct the astigmatism.
PD (Pupil distance)
Visual strength vs. visual acuity
The glasses prescription receipt will mention the visual strength, which importantly should not be confused with visual acuity. These are two different concepts. Read about the different on the page: ‘Difference between visual strength and visual acuity’.