What Is the Astigmatism Axis?

The astigmatism axis represents the axial direction of the lens, which is based on the direction where your cornea has the greatest curvature and the weakest refractive power. Astigmatic eyes see lines in a certain direction are clear or blurred, depending on the axis and degree of astigmatism. In general, the direction of astigmatism on the watch's blurred lines is the direction of the axis of the negative cylinder lens worn by the eye. For example: a 1.ODC × 180 astigmatism eye, the astigmatism power is in the vertical meridian, and the horizontal meridian is face up. In other words, the astigmatic eye has stronger vertical meridian power than horizontal meridian power. 1. 1. When the astigmatism eye of ODC × 180 degree looks at the astigmatism table, the vertical lines are clear and the horizontal lines are blurred. This is the reason for using the astigmatism table to determine the astigmatism axis.

Astigmatism axis

The astigmatism axis represents the axial direction of the lens according to your cornea

Introduction to the astigmatism axis

The axial position of astigmatism can generally be determined by adjusting the lenses on the test frame, but this method is relatively subjective, and many people with astigmatism cannot easily distinguish between blur and clarity. Sometimes sleep, weather, emotions, and physical conditions can affect a patient's judgment. Coupled with long optometry times, the accuracy is lower. Astigmatic eyes see lines in a certain direction are clear or blurred, depending on the axis and degree of astigmatism.

Astigmatism axis parameters

Astigmatism axis

Astigmatism axial refractive error table

Maximum tolerance for refractive error in both eyes 2.50D

1. Symmetric astigmatism: 180

A symmetry law-10 / 170

B symmetry inverse law -85/95

C symmetry oblique astigmatism -130/50

Tolerable limit in oblique axis state 2.25D

Coaxial astigmatism

A coaxial coherent astigmatism 180

B coaxial inverse astigmatism 90

3. Asymmetry coaxial astigmatism, astigmatism is greater than the sum of 180

Degree of asymmetry ("30"

A Coaxial Astigmatism-180/30, 120/85

1) Coaxial astigmatism -5/155, 95/115

2) coaxial astigmatism in the same area-5/25, 95/115

B coaxial inverse astigmatism-90/65, 5/150

1) Astigmatism in different directions in the same direction -115/85, 25/175

2) Astigmatism-65/85, 150/175

3) Coaxial oblique astigmatism 55/145

Binocular tolerance limit 2.00D

4.Asymmetric astigmatism 180/100, 70/170

A Anisotropic astigmatism 110/5, 80/165

B Anisotropic astigmatism 85/5, 100/155

5. Heteroaxial astigmatism, one axis 180, one axis 90

Binocular tolerance limit 1.00D

6. Parallel astigmatism, 60/60

7.Oblique axial astigmatism. 135/45.

Binocular tolerance limit 1.25D

Astigmatism axis-relationship between astigmatism axis and age

Did you notice in clinical practice: Generally, astigmatism in young people is astigmatism (negative astigmatism is close to 180 degrees in the axial direction), and astigmatism in older people is often astigmatic astigmatism. What is the reason?

The tension of the eyelids of young people is large. The eyelids exert an upward and downward squeezing force on the cornea when blinking or when the eyes are closed. Long-term micro force causes the cornea to become steep in the vertical direction and flat in the horizontal direction. As a result, the direction of astigmatism is horizontal. (The direction of astigmatism is the direction in which the cornea is relatively flat).

With the increase of age, the eyelids gradually relax, and the squeezing force on the cornea gradually decreases, causing the astigmatism to shift from the axial direction to the vertical orientation.