Cornea 490 refers to the thickness of the cornea of 490 microns, if the myopia is high, it is not recommended to do semi-femtosecond surgery, and those with low myopia should ask the doctor carefully whether the surgery can be performed, so the specific ability to perform femtosecond surgical treatment is related to the condition of the patient. Corneal thickness of 490 microns is lower than the normal population, while the semi-femtosecond surgery needs to cut the corneal tissue, the higher the myopia, the more corneal tissue is cut off, the cornea is too thin, which will lead to corneal edema, and complications such as cone cornea and rupture of the cornea can also occur. Therefore, if the patient is highly myopic, semi-femtosecond surgery may not be recommended, while those with lower myopia can choose according to the doctor’s advice. There are many ways to correct myopia, semi-femtosecond surgery is only one of them, patients can also use IOL implantation and other ways to correct myopia. It is recommended that myopia patients seek timely medical attention to assess their condition and follow the doctor’s instructions to choose the appropriate treatment.