1 Composition And Function Of Astigmatism Meter

The astigmatism meter is composed of some lines representing a certain direction. The included angles of two adjacent lines are equal, and the thickness of the lines is the same as that of the sight mark line in the far vision table 1.0 (1 point of view). The commonly used astigmatism meters are clock type and radiation (sector). The astigmatism meter is helpful to check whether there is astigmatism, the axial position of astigmatism correcting cylindrical lens, the refractive power of astigmatism correcting cylindrical lens, etc.

2 Operation Steps

a. Objective examination of both eyes and preliminary correction (astigmatism meter may not be used if there is large astigmatism). First the right eye, then the left eye.

b. Fog optometry: gradually reduce the added spherical mirror and observe whether the visual acuity is significantly improved. If it is not significantly improved, there may be large astigmatism.

c. Project red and green visual markers to prevent myopia from being overcorrected. Generally, red and green are equal or red visual markers prefer a little (further determine the spherical lens).

d. The projection astigmatism meter allows the subject to observe whether there is a difference in the depth of the lines.

e. Instruct the subject to point out the axial direction of the black, thin and clear lines, and apply the 30x rule to determine the axial direction of the cylindrical lens test piece.

f. After the axial direction is determined, increase the focal power of the cylindrical lens with a gradient of -0.25d until the line clarity of each axial direction of the astigmatism meter is consistent.

3 Note

a. If the existence of large astigmatism can be accurately judged by objective optometry, it can be checked without astigmatism meter.

b. If there is high myopia or hyperopia and low astigmatism, the myopia or hyperopia shall be preliminarily corrected to make its vision above 0.7, and then the astigmatism meter shall be used.

c. Before the application of astigmatism meter, it should be combined with fog for preliminary correction, and then combined with red and green visual mark detection.

d. The method of measuring the degree of astigmatism and axial position with astigmatism meter has its limitations. For large astigmatism, due to poor vision, it is difficult to distinguish the lines of astigmatism meter.

e. The astigmatism meter only preliminarily determines the axial position and refractive power of astigmatism. If some subjects have mild astigmatism and have no obvious reaction when looking at the astigmatism meter, they should be judged in combination with objective optometry and the rotation axis position of the equivalent spherical lens.