After more than 20 years of development, keratoconus surgery is recognized for its safety, effectiveness and predictability. Strict preoperative examination is the foundation of the surgery. Before the examination, we should pay attention to: 1. Rest well before the examination, do not stay up late and overuse your eyes. 2. Patients who often wear corneal contact lenses need to stop wearing contact lenses until the cornea is edema-free, refractive status and corneal topography are stable before undergoing surgery. It is recommended to stop wearing soft spherical lenses for more than 1 week, soft toric lenses and rigid lenses for more than 3 weeks, and keratoplasty lenses for more than 3 months before surgery. History of refractive error and correction – History of eye surgery – History of eye diseases – History of systemic diseases and family history, medication history – History of adverse drug reactions and allergies – Occupation, life and eye habits, etc. 1.2 The following tests should be done before surgery: – Naked eye distance and near visual acuity – Subjective and objective optometry – Best corrected visual acuity – Eye position – Primary eye – External eye Slit-lamp eye examination – Posterior pole and peripheral fundus examination – Intraocular pressure measurement – Corneal thickness measurement – Corneal topography 1.3 The following tests are recommended for those who are able: – Ciliary muscle palsy optometry – Anterior and posterior corneal surface morphology and analysis of anterior and posterior eye segment measurements – Contrast sensitivity and glare examination – Corneal endothelial examination – Wavefront aberration examination – Eye axis measurement – Tear function examination – Pupil diameter measurement; including Pupil diameter in dark light – Eye adjustment amplitude examination.