Myopic arcs are the most common fundus change in myopic eyes. The smallest are not easily visible, and the largest can reach the size of the optic disc. Some surround the optic disc, or even reach the macula. If the myopic arc does not invade the macula, it has little effect on visual acuity; if it invades the macula, visual acuity (including near vision) is significantly reduced. Generally speaking, it is difficult to affirm whether myopia is still in progress based on the shape of the arc alone. However, based on fundus observation, if the margins are clear, it can be presumed that myopia has stopped progressing; conversely, if the margins are irregular, the elongation of the eye may still be in progress. When the extent of the myopic arc is large, especially when a scleral cone or post-scleral staphyloma has formed, it appears that the optic disc is not squarely round but becomes a longitudinal oval due to the tilting of the optic nerve canal. The degree of myopia and the myopic arc are diagnosed based on: 1. The width of the myopic arc is positively correlated with the degree of myopia; 2. The mild myopic arc spot is only jaw side change, except for the atrophic arc of high myopia, which can appear in the upper and lower part of the optic disc, even on the nasal side; 3. This method is objective and sensitive in evaluating the axial changes of myopia.