Mixed astigmatism is a condition in which light rays are refracted through the refractive interstitium of the patient’s eye to form a focal line into the eye, with the anterior and posterior ends of the focal line being located in front of and behind the plane of the retina, respectively. Astigmatism is a common ophthalmologic condition and is a type of refractive error. It is usually caused by abnormal corneal development, i.e., a difference in the refractive power of the cornea in the vertical direction and the horizontal direction, which results in the refracted rays of light entering the eyeball not being able to converge to form a focal point but rather forming a line of focus. There are three types of astigmatism: myopic astigmatism, hyperopic astigmatism and mixed astigmatism. If all the lines of focus are in front of the retina, it is called myopic astigmatism, if all the lines of focus are behind the retina, it is called hyperopic astigmatism, and if both ends of the lines of focus are in front of the retina and one end is behind the retina, it is called mixed astigmatism. Mixed astigmatism has a greater impact on vision, so it is recommended to go to a formal institution for examination and prescription of corrective lenses.