Understanding Prescriptions

Your Prescription

A usual contact lens prescription will contain the lens brand name, base, diameter and any other information required.


Standard lenses

Acuvue Oasys R 8.4 / 14.0 / -2.00 L 8.4 / 14.0 / -2.50
Some lenses like the Acuvue Oasys above only have one possible base and diameter and thus the prescription could be written as follows.
Acuvue Oasys R -2.00 L -2.50


Toric lenses to correct Astigmatism

Purevision Toric R 8.7 / 14.0 / -1.00/-0.75 x 180 L 8.7 / 14.0 / -1.75/-1.25 x 10
or as the Purevision Toric has only one possible base and diameter it could be written as follows.
Purevision Toric R -1.00/-0.75 x 180 L -1.75/-1.25 x 10

Only the possible options for base and diameter are displayed on the lens ordering page.


Common Prescription Parameters Explained

Lens Type is the brand name of your lens and will be specified on your prescription. Some examples are Acuvue Advance, Focus Night & Day and Freshlook Colors

R - indicates the right eye. Sometimes written as O.D. 
L - indicates the left eye. Sometimes written as O.S.

Power sign Either + (plus) or - (minus)

Sphere (Sph) is a number between +20.00 and -20.00. Plano means the lens has no optical power and does not correct vision.

Cylinder (CYL) is a number between -0.50 and -4.00 and is only found in Toric Prescriptions to correct astigmatism.

Axis (Axis) is a number between 1 and 180 and is only found in Toric Prescriptions to correct astigmatism.

Often the Sphere, Cylinder and Axis of prescriptions will be written all together in the following form:
 SPH / CYL x AXIS and will look something like -1.00/-0.75 x 90.

ADD (Add) is a number between +0.50 and +4.00 only found in Bifocal or Multifocal lens prescriptions

Base Curve (BC) is a number between 7.0 and 9.5 which determines the looseness or tightness of a contact lens.

Diameter (DIA) is a number between 13.0 and 15.0 and is the diameter of the contact lens.

Lens Tinting is the tint or colour of the contact lens. Some lenses are clear and most have a very light tint called a visitint which allows you to see the contact lens slightly more easily when handling it. Tinted contact lenses have a variety of colours to choose from to change your natural eye colour.