What Is the Average Eye Measurement for Contact lenses?

Your eye care professional uses specific measurements to customize contact lenses so they will fit properly on your eyes. There are several types of measurements used to determine your individual contact lens prescription.

K-Readings

• An eye doctor will use a keratometer, also called an ophthalmometer, to measure the curves of your cornea, the clear outer layer of your eye. Based on the measurements, referred to as K-readings, the doctor determines the curve of your contact lenses. Average curvature measurements range between the numbers 41.00 and 45.00.

Curvature

• K-readings are transposed into a measurement called a base curve for contact lenses. The base curve is expressed in millimeters. The lower the number, the steeper the curve. Base curves average between 8.0 and 10.0 millimeters.

Power

• Lens power is the strength of your prescription, measured in diopters. The larger the number, the stronger the correction needed to improve your vision. Power can range from 0.00 to 20.00 or higher, but average contact prescription strength is between 2.00 and 4.00 diopters.

Diameter

• The diameter of a contact is the distance across the lens in millimeters. Average eye measurement for diameter yields a size between 12 and 14 millimeters. Diameter is important for proper fit of the lens. If the lens is too small or too big, it can cause irritation or damage to the eye.

Considerations

• Contact lens measurements are specific for each person, and although there are average sizes, many factors can influence the final fit of a lens. Eye doctors require new measurements every year or two because the fit and size of your lenses can change.