I. Visual acuity examination including bare eye visual acuity and best corrected visual acuity with glasses. Second, eye pressure examination to exclude the possibility of high eye pressure and glaucoma. Refractive examination includes computerized optometry, medical optometry and dilated optometry. The correctness of optometry directly affects the effect of surgery. 4.Ocular segment and fundus examination Focus on corneal transparency, corneal scars, cloudy crystals, fundus examination for vitreous turbidity and fundus lesions, etc. V. Wavefront aberration examination Check whether there are higher-order aberrations that seriously affect visual quality, in addition to lower-order aberrations such as myopia, hyperopia and astigmatism, and collect higher-order aberration data as the basis for diagnosis and surgery. Corneal curvature examination will be performed to exclude the possibility of conical cornea and flat cornea. Seven, corneal thickness measurement If the patient is highly myopic, attention should be paid to the central cutting depth of the cornea, and the relevant information should be explained to the patient before surgery. The main purpose of corneal topography is to understand the regularity and symmetry of the entire corneal surface and to exclude abnormalities such as cone corneas. LASIK is not suitable for all patients with refractive errors such as myopia, hyperopia, astigmatism, etc. Only patients with the following three conditions are suitable for LASIK: ①, age 18 years or older ②, relatively stable refractive status in the past two years (no significant change in prescription) ③, no contraindications to LASIK such as active inflammation of the eye, such as acute conjunctivitis, keratitis, etc. ③, no contraindications to LASIK such as active inflammation of the eye, such as acute conjunctivitis, keratitis, etc.; cone cornea, glaucoma, severe dry eye, etc.; severe amblyopia with very poor corrected visual acuity; scarring, diabetes, collagen disease; proptosis, incomplete eyelid closure; one-eyed patients, etc.