In addition to poor distance vision, high myopia is often associated with poor night vision, flying mosquitoes, floating objects in front of the eyes, flashing sensation and other symptoms, and can occur with varying degrees of fundus changes. The risk of retinal detachment, tears, fissures, macular hemorrhage and neovascularization is much higher compared to normal people. Posterior scleral staphyloma is often formed due to a longer anterior and posterior diameter of the eye, a more prominent eye, and dilatation of the posterior pole of the eye. Those with the above clinical manifestations are called pathological myopia, while those without obvious above manifestations are called simple myopia. The main danger of high myopia lies in the complications. In addition to the general low visual function such as distance vision and the characteristic signs (leopard-like fundus and arcuate spots of the optic disc), there are various complications of myopia. They usually increase and worsen with increasing refractive error and age, leading to more visual impairment. In addition, chorioretinal degeneration, macular degeneration and retinal detachment can lead to blindness. The pathological basis of complications is mainly the prolongation of the eye axis, impaired blood circulation, malnutrition and specific tissue degeneration. The common types include: 1) vitreous, choroidal and retinal degeneration due to structural abnormalities and nutritional disorders; 2) macular degeneration and atrophy and posterior pole staphyloma due to prolongation of the eye axis, scleral elongation and biomechanical abnormalities; 3) amblyopia and strabismus due to low visual acuity, refractive aberration and convergence dysfunction, which can be considered as complications of myopia. They can also be attributed to the signs of degenerative myopia itself, which has a complex causal relationship.