The cornea is an important refractive medium of the eye. Corneal thickness can be used in the diagnosis of many diseases and in the preoperative preparation of keratoconus surgery. Under normal conditions, the central corneal thickness in adults is 0.5 mm and the peripheral thickness is about 1.0 mm. Corneal thickness can be examined by the following methods: i. Ultrasonic corneal thickness gauge, which is currently the most commonly used method; ii. Optical measurement; iii. Ultrasonic biomicroscopy measurement; iv. Optical coherence tomography examination; v. Contact or non-contact corneal endothelioscopy measurement method; sixth, Dr. Lund’s anterior segment analysis and diagnosis system. All of these methods can provide accurate measurements of corneal thickness.