- 1). Check the sphere section of your eyeglass prescription. Abbreviated as SPH, the information in this section is typically represented by a decimal with a plus sign or minus sign in front of it. The decimal represents the power of your lens, measured in increments called diopters and the plus and minus signs mean that you are either farsighted or nearsighted, respectively. Thus, -3.00, for example, in the sphere portion of your eyeglass prescription would mean that you have three diopters of nearsightedness. Conversely, a reading of +3.00 would mean that you have three diopters of farsightedness.
- 2). Notice if there is any information listed in the cylinder and axis sections of your glasses prescription. Cylinder and axis refer to information regarding astigmatism, which is an irregular curvature in your cornea. Cylinder, abbreviated CYL is represented by either a positive or negative decimal and is also measured in diopters. According to Eye Buy Direct, "the axis value indicates where your astigmatism is located along your eye's horizontal axis." Axis is expressed as a numerical value ranging from one to 180 degrees. If you do not have astigmatism, your optometrist will leave the cylinder and axis boxes of your prescriptions blank.
- 3). Review the prism and base sections of your prescription."While the prism value refers to the displacement of the image through the lens, the base value refers to the direction of this displacement," according to Eye Buy Direct. If you do not suffer from muscular abnormalities in the eye, such as strabismus, your ophthalmologist will not fill in these boxes.
- 4). Check the add box of your prescription. Short for addition, add refers to the power added to prescription bifocals or multifocal glasses. Add power is measured in diopters.
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