You may be unfamiliar with the cylindrical lens, or you may not have heard of it. One surface of the cylindrical lens is a flat surface, and the other surface is a lens with an arc surface. What is the function of the cylindrical lens, and what does the cylindrical lens mean? Today, I will take you to understand it. In addition to concave and convex lenses, cylindrical lenses are also a type of vision correction. In life, there are many types of refractive errors, the most common of which are myopia, hyperopia, astigmatism and so on. For myopia, a concave lens can be used to shorten the distance between the object and the retina, and the imaged object can be seen in front of the retina, so that distant objects can be seen clearly. The convex lens is mainly for hyperopia, its principle is exactly the opposite of that of the concave lens, but the function is to enable the eyes to see the object clearly, but the concave lens is to see the distance, and the convex lens is to see the near. In addition to myopia and hyperopia, astigmatism is one of the most common types of refractive errors in people's lives. The cylindrical lens is developed for astigmatism, which can effectively correct astigmatism and remove astigmatism in the eye. Because the cylinder has no curvature, when the light passes through the cylinder, there is no curvature in this direction, but the direction perpendicular to the axis has the greatest curvature, so the light is subject to the greatest curvature when passing through the cylinder. It is to use this feature to correct astigmatism, and the effect is also obvious. To sum up, the cylindrical lens, like the concave lens and the convex lens, also has the effect of correcting the refractive errors that are common in life. Refractive errors mainly include myopia, hyperopia and astigmatism. Among them, astigmatism is corrected by cylindrical lenses, which is currently the most widely used and the best way to correct astigmatism.