How is astigmatism measured?
Nov 19, 2025
Source: Cainiu Health
Dr. Wang Lei
Introduction
In a prescription for eyeglasses or an optometry report, the astigmatism value is indicated first by a number (in diopters), followed immediately by the axis value (ranging from 0 to 180 degrees). For example, "-1.00 DC × 180°", where the number represents the degree of astigmatism and the axis notation specifies the direction of astigmatism, enabling precise correction of irregular corneal refraction during lens fitting and ensuring that the lenses accurately match the eye's actual condition.
Generally, astigmatism is expressed numerically in diopters, along with the axis notation, together forming a complete astigmatism prescription. There is no single fixed format for representation. If in doubt, it is recommended to consult a medical professional in advance. Detailed analysis is as follows:
In an eyeglass prescription or optical refraction report, astigmatism is typically indicated by a numerical value (in diopters) followed immediately by the axis value (ranging from 0 to 180 degrees). For example, "-1.00 DC × 180°", where the number represents the degree of astigmatism and the axis specifies its orientation. This allows precise correction of corneal irregularities during lens fitting, ensuring that the glasses accurately match the eye's actual condition.
When referring to astigmatism alone, it may be simply stated as a number with units, such as "100 degrees of astigmatism." This simplified expression is common in everyday conversation but lacks axis information and cannot be used directly for lens ordering. During eyeglass fitting or professional examination, both the degree and axis must be clearly specified; otherwise, inadequate correction may occur, potentially worsening visual discomfort.
After obtaining astigmatism measurements in daily life, confirm whether axis information is included—do not order glasses based solely on spherical power. Regularly visit qualified institutions for eye examinations to update astigmatism parameters. If symptoms such as increased double vision or frequent eye fatigue occur, promptly recheck both the degree and axis of astigmatism to ensure the corrective plan remains suitable for your current eye condition.
