Understanding your prescription
Your prescription can be written in different ways. Here is a short explanation as to how to interpret your prescription.
Right and left eyes
The right eye may be written as right, R, RE or OD. The left eye may be written as left, L, LE or OS.
Base Curve
Base curve (BC) is sometimes included on contact lens prescriptions. The BC is the overall curvature of the lens. If it is not included on your prescription, leave this field blank.
Diameter
Diameter is the measure of the distance across the contact lens.
Sphere
The sphere (SPH) is usually a + (plus) or - (minus) number, and may be the first number on your prescription (after BC and diameter). If there is a fraction, it is the top number. The sphere may be 0.00 (or plano or pl) or sometimes left blank.
Cylinder
The cylinder (CYL) is usually the second number in the prescription, after the sphere. If there is a fraction it is the bottom number. Not every prescription includes a cylinder, or sometimes there may be a cylinder in only one eye.
Axis
You will only see an axis if you have a CYL. The axis is the number shown after the CYL, usually preceded by an X. It will be between 0 and 180.
Add
An add is included in some contact lens prescriptions. The add is the additional power that provides a reading prescription for those who need it. With contact lenses, this may be a number, or it may be written as Low (L), Med (M) or High (H). If there is only one value on your prescription, enter this for both eyes.