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Contact Lenses


Contact Lenses
Fitting Contact Lenses
Contact Lens Prescription
Contact Lens Complications
Caring for Contact Lenses

Contact Lens Prescriptions

For the untrained eye, prescription contact lenses can be very confusing. There are only a few simple details one needs to understand in order to understand what their prescription means.

A prescription will look something like this.

OD -6.40 -2.00 90 +1.10
OS -7.00 -1.00 180 +1.00
BC 8.6 DIA 14.2

Follow the legend below:

OD is for the right eye OS is for the left eye OU refers to both eyes



The first number (-6.40) refers to the refractive power. It is measured in diopters.

A negative value indicates myopia
A positive value indicates hyperopia
The number indicates the amount. The farther from zero the number, the greater the amount.

The second number (-2.00) indicates the amount of astigmatism (if any exists). It is measured in diopters. Astigmatism is present if the shape of your eye is like a football, as opposed to a sphere. The third number (90) is a measurement of the axis of astigmatism in degrees. An axis of 180 is horizontal. An axis of 90 is vertical.

The last number on the top line (+1.10) indicates reading power (if any exists) for a bifocal lens.

BC is the base curve (radius) of a contact lens. It is measured in millimeters.

DIA is the diameter, measured in millimeters. Consumers should be wary about buying contact lenses without a prescription. Only nonprescription lenses should be purchased without a contact lenses prescription. It is important to understand your prescription contacts so that you can ensure that you are getting the product you require to meet your vision requirements.


The National Eye Institute (A Division of the National Institutes of Health) offers excellent resources about vision, eye care and contact lenses. This site is available in both English and Spanish. The Optometrists Network provides detailed information for parents about children and vision care.




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