Contact Lens Info

When you visit your eye doctor, he’ll jot down a number of different numbers down on paper during your eye exam to describe what you’re seeing and what you can’t see. Knowing some contact lens info about your prescription can help you quickly comparison shop for your contact lenses over the phone or on the internet.

When you read your prescription for your contact lens info, you’ll see O.D. and O.S. O.D. means your right eye, and O.S. means your left eye. You might see the abbreviations RE and LE, too, beside your right eye numbers and your left eye numbers.

Contact Lens Info

Your contact lens information O.D. line might appear something like sphere +2.50, cylinder +1.00 and axis 180. The sphere is how nearsighted or farsighted you are. Cylinder is the measurable degree of astigmatism of your central cornea. The cylindrical number describes the dioptric difference between your cornea’s steepest and lowest curves. If you have astigmatism, your cornea is shaped like the back of a spoon and is curved more on one side than on the other.

The power of your lens is measured in unites called iopters. Diopters are based on the extent that light rays pass through the lens will be bent. As the power of the lens increases, so does the thickness of the lens.

Toric Contact Lens Information

In the above example, your right eye has 1 ¼ diopters of nearsightedness with 2 ½ diopters of astigmatism. The axis is the orientation of the cylindrical area of the lens. The axis can be anywhere from 1 to 180 degrees, with 90 being the vertical meridians.

Convex lenses are thicker in the center than at the edges, like magnifying glasses. Light rays are gathered together toward a central point. Convex lenses are used in glasses for farsighted eyes that can’t bend light rays as much as they need to. They are illustrated with a + sign on prescriptions.

Concave lenses are thinner at the center than at the edges and spread light rays apart. These lenses are used for eyes that are nearsighted. Concave lenses are indicated with a – symbol.

Cylindrical lenses are curved more in one direction than the other. To tell if your lenses are cylindrical, hold your glasses at arm’s length and sight a straight line through the lens. Rotate the glasses clockwise and counterclockwise. If the line bends, it’s a cylindrical lens.