Common refractive disorders of the eye such as nearsightedness or myopia, farsightedness or hyperopia, astigmatism, and the age dependent need for reading glasses or presbyopia are measured in units called diopters. Diopters represent the amount of correction you need to clear your vision. The more nearsighted, farsighted, or astigmatic you are, the higher your prescription in diopters.
Your prescription is written in three numbers:
For example, -5.00 -1.50 x 180 represents a typical prescription.
The first number (-5.00) identifies your degree of nearsightedness or farsightedness. The sign identifies whether you are nearsighted (- sign) or farsighted (+ sign).
The second number (-1.50) identifies your degree of astigmatism. The number can be written either with a + sign or a – sign.
The third number (180) is the axis, which indicates the direction of your astigmatism. An axis of 180 degrees, for example, means the astigmatism is horizontal.
Therefore, -5.00 -1.50 x 180 means that the patient is moderately nearsighted, with a moderate degree of astigmatism in a horizontal direction.
