The principle of how the eye sees starts with the structure of the eye, from front to back, the eye can be divided into cornea, lens, vitreous humor, retina, and optic nerve. If we compare the eye to a camera, the lens is equivalent to the lens of the camera and the retina is equivalent to the negative of the camera. The refraction of parallel light rays through the lens and cornea results in an image that falls on the retina, and the resulting information is transmitted through the optic nerve to the visual center. This then feeds back to the surface of the retina to form an object image, and the eye can see things, and this is the principle of how the eye sees things. Therefore, if there are lesions in different locations of the eye, it will lead to different degrees of vision loss, and a detailed examination is needed to clarify the cause of the disease before symptomatic treatment can be given.