With the continuous release of electronic devices, an increasing number of people are suffering from myopia and other eye diseases. When our eyes develop myopia and other similar conditions, we must seek immediate treatment and correct the myopia as soon as possible. If we do not start treatment early, myopia will become increasingly severe. Myopia can be identified by the degree of myopia table. How can we determine whether we have myopia by looking at the myopia table?

1. Not wearing glasses to see the astigmatism chart:

If all the line frames are of equal size, it indicates that there is basically no astigmatism (50 degrees).

If at a certain distance, it is found that a line frame or two line frames around it on the astigmatism chart are black and clear, while the other line frames are lighter in color or even blurred, it indicates that there may be astigmatism. The more significant the difference between the clear line frame and the light-colored line frame, the more severe the astigmatism.

2. Wearing myopia glasses to see

The same principle can be used to determine whether your myopia glasses have adequately corrected your astigmatism.

Note that when the distance of the astigmatism chart is within the adjustment range of the eyes, the eyes may unconsciously adjust the lens focal length, causing the lens focal length to be between the long focal length and short focal length of the astigmatism, thus weakening the astigmatism effect. Therefore, people with myopia accompanied by slight astigmatism may be able to feel the effect of astigmatism more significantly at a certain distance without wearing glasses; while wearing glasses without astigmatism, because the adjustment distance becomes longer after wearing myopia glasses, it may feel that the astigmatism effect is not significant. However, people with higher astigmatism can feel it significantly regardless of how they think.

In fact, the basic principle of the astigmatism chart can be analyzed by integrating the Spherochromatic chart. According to the Spherochromatic chart, you can understand that the positions of the two vertically aligned frames on the astigmatism eye’s fundus are different, one in front and one in the back, with a distance difference in the middle. This distance difference is directly proportional to the degree of astigmatism. Which line frame is clearer to the human eye depends on their distance to the macula of the fundus. The one closer to the macula of the fundus will feel clearer.

For example, in the case of an astigmatism eye with -1.00DC*180, when looking at the astigmatism chart, due to the lack of diopter in the horizontal direction, the vertical line frame will immediately appear on the macula of the fundus, so the vertical line frame is clear. Conversely, there is -1.00DS in the vertical direction, so the line frame in the horizontal direction appears in front of the macula of the fundus, making the line frame in the horizontal direction blurred. In the actual operation of the vision examination, the patient will say that the line frame at 6 o’clock or 12 o’clock is the clearest.

This is an example of simple myopia with astigmatism, and the condition of mixed astigmatism is actually the same, except that the two vertical frames are not on the macula of the fundus. Assuming that a patient’s binocular diopter is -1.00DS-1.00DC*180, then the binocular vision of such a patient looking at the astigmatism chart will have both vertical and parallel lines in front of the macula of the fundus, but the line frame in the vertical direction is closer to the macula of the fundus, theoretically with a distance of 0.333mm, while the line frame in the parallel plane direction is farther from the macula of the fundus, theoretically 0.667mm. Since the line frame in the vertical direction is closer to the macula of the fundus, it will feel clearer, and in the actual operation of the vision examination, the patient will also say that the part at 6 o’clock or 12 o’clock is the clearest.