Understanding your Prescription
A prescription for eyeglasses or contacts indicates the degree your eyes are out of focus and contains the specifications of lens strength required to correct your vision.
O.D. and O.S. are latin abbreviations for the right and left eye, respectively. A prescription from your optometrist may contain one or more numbers for each eye. An example would be: -2.00 / -1.00 x 180
The first number (i.e. -2.00 in the example) refers to the lens power required to correct your nearsightedness or farsightedness. A negative number means you are nearsighted, or that you have difficulty seeing distant objects. A positive number indicates farsightedness, or difficulty seeing close objects comfortably. The higher the first number is, the stronger the lens power will be.
The second number (i.e. -1.00 in the example) is a measure of your astigmatism, an uneven shape of the surface/s in your eye that results in blurred vision. Many people who are nearsighted or farsighted also have some astigmatism.
The third number (i.e. 180 in the example) ranges from 0 to 180 and represents the axis (in degrees) of your astigmatism.
Contact Lens Prescriptions
Your contact lens prescription differs from an eyeglass prescription and can only be obtained during a contact lens consultation and fitting.
In addition to the information in your eyeglass prescription, your contact lens prescription also contains:
Information specifying the central curve of the contact lens’ back surface
The contact lens diameter
The manufacturer and/or brand name of the contact lens
As contact lenses rest directly on your eye, the strength of your contact lens prescription can differ from your eyeglass prescription.
If you have further questions about your prescription, speak to your doctor.