(1) Simple myopic astigmatism: a major meridian of parallel rays imaged on the retina, and another meridian of parallel rays perpendicular to it in front of the retina focus imaging. (2) Simple hyperopic astigmatism: a major meridian of parallel rays on the retina is imaged, and another meridian of parallel rays perpendicular to it is imaged in the retina posterior focus. (3) Astigmatism symptoms of compound myopic astigmatism: two parallel rays on the main meridian perpendicular to each other are imaged in front of the retina, but their refractive power is not equal. (4) Astigmatism symptoms of compound hyperopia astigmatism: the parallel rays are imaged behind the retina on two mutually perpendicular major meridians, but their refractive power is not equal. (5) Astigmatism symptoms of mixed astigmatism: two mutually perpendicular major meridians, one parallel ray is imaged in front of the retina, and the other meridian parallel ray is focused behind the retina. The symptoms of astigmatism include visual fatigue, headache, and blurred double vision. Because the retina cannot form a clear image, patients often squint their eyes into a slit in order to see more clearly. Many patients do not know the reason for this, and often complain that their glasses are low. If your vision is diminished and you have symptoms of visual fatigue, you should have a dilated eye exam. Through the examination, you can accurately know the presence or absence of astigmatism, the degree of astigmatism, and also check whether there is a combination of myopia or hyperopia, and can be corrected with glasses according to the results of the examination. Myopia or hyperopia can be corrected at the same time as astigmatism. Currently, the most effective solution is to correct the astigmatism with glasses in time. (1) The patient often has the habit of squinting the eyelids into slits in an attempt to make the object clearer. (2) Visual acuity loss: The color of the visual marker in the direction of the focal line away from the retina becomes lighter, the edge of the focal line becomes blurred, and it is not easy to recognize, the visual acuity decreases, and in severe cases, diplopia occurs. In addition to physiological astigmatism, all kinds of astigmatism can easily cause vision loss. Farsighted astigmatism has better vision than myopic astigmatism due to the effect of adjustment. For example, if the astigmatism is 1.00 degrees, the visual acuity of farsighted astigmatism is about 0.8, while that of myopic astigmatism is about 0.5. When looking at the sight mark with oblique astigmatism, the sight mark is easily distorted. The phenomenon of “long hair” often results in reduced visual acuity because of the distortion. Therefore, it is especially important to correct the axis of oblique astigmatism. (3) Visual fatigue; astigmatic eyes due to the different refractive power of each meridian on the refraction of parallel light can not form a focal point but two focal lines, so the brain is easy to produce a selective reading of the image. The reason is that astigmatism tends to produce a scene in the direction of the focal line of the near retina; in addition, astigmatism uses the adjustment to reduce the size of the diffusion circle as much as possible to improve the quality of the image in order to see the scene clearly; high astigmatism is easy to cause headache if it is not corrected properly or not wearing a lens. Therefore, astigmatism is easy to produce visual fatigue. (4) Amblyopia: Mostly seen in high astigmatism, especially hyperopic astigmatism, because it is not clear to see far and near, vision is not exercised. Amblyopia easily occurs, followed by a tendency to strabismus.