Visual acuity S, C, A refers to the degree of spherical lenses, the degree of cylindrical lenses and the direction of astigmatism axis respectively, which are the main indexes tested in optometry.
1.S: Spherical lens, that is, myopia or hyperopia, commonly used + on behalf of hyperopia, – on behalf of myopia, the normal value is generally related to age, such as 3-year-old children generally have 300 degrees of hyperopia reserve, 12-year-old children S generally reach 0 degrees.
2.C: the degree of column lens, the normal value is 0, if the degree is abnormal, it means that the phenomenon of astigmatism, commonly used + on behalf of the number of degrees of hyperopic astigmatism, – on behalf of the number of degrees of myopic astigmatism.
3.A: astigmatism axis direction, usually related to the corneal curvature, generally have astigmatism have astigmatism axis, if the direction of astigmatism axis is inaccurate when matching glasses, it may cause blurred vision, plus fatigue.
The above three indicators can help determine the condition of myopia, hyperopia and astigmatism, and you should pay attention to the scientific use of eyes to protect your eyesight.