Myopia of 600 degrees or more is called high myopia. The division of myopia is: less than 300 degrees is called low myopia, 300 degrees to 600 degrees is moderate myopia, and 600 degrees or more is high myopia. Because the perimeter of the eye is longer in high myopia, people with high myopia can also have combined eye diseases such as retinal degeneration, retinal fissures, retinal detachment, vitreous liquefaction, and other diseases. High myopia is not only a refractive problem, but also often results in structural lesions of the eye, so people with high myopia often have retinal detachment. The causes of high myopia are as follows: 1. Genetic causes: It is common to see a family wearing high myopia glasses, which is determined by genetic factors; 2. Environmental factors: The parents are not highly myopic, but the child is highly myopic, which is an acquired factor, high myopia caused by environmental factors. In short, myopia of 600 degrees or more is called high myopia.