Your Prescription - What Does It Mean?

Have you ever left your eye exam appointment wondering what all the numbers and terms on your prescription for eyeglasses really mean? Here are common terms that will help you understand your prescription:

Sphere

The large back-side sphere-like curve which is the foundation of most lens corrections, sometimes also called "power." Sphere is measured in units called diopters and can be positive or negative, representing the severity of the curve of the lens. Generally, positive (+) number diopters correct farsightedness (hyperopia), and negative (-) number diopters are shaped to correct nearsightedness (myopia).

Cylinder

A cylinder shaped band of high or lower diopter, that may be added to a lens to correct for astigmatism. It may be left blank or have "DS" meaning no Cylinder correction is necessary.

Axis

A further definition of Cylinder to correct an astigmatism that signifies the angle of the correction, ranging between 1 and 180 degrees. Without a Cylinder this will be left blank.

Prism

A correction to assist the eyes in working together, for example to correct an eye muscle imbalance, or in cases of strabismus or binocular diplopia. Prism works by moving the perceived location of what is being seen relative to the other eye. Prism will be left blank if this type of correction is not recommended.

Base

The measurement of the curvature or diopter of the front of a lens, sometimes used to allow certain prescriptions in specific frames depending on the surface area of the lens. Base may be diffrent from one pair of frames to another even though the rest of the prescription is the same, so it is often left blank at the time a prescription is written.

Multifocal

Some eyeglass prescriptions (such as those that correct presbyopia) have multiple Spheres each correcting for different ranges of vision. For more information on Multifocal, Bifocal, Trifocal, and Progressives click here.