Corneal thickness was more and more valued by ophthalmologists in the preoperative examination of corneal refractive surgery.Currently,there are many instruments used to measure corneal thickness,and most of them can be roughly divided into two categories.One is based on the principle of ultrasound,including the traditional ultrasonic corneal pachymetry and ultrasound biomicroscope(UBM),and the other is based on the optical principle,such as Orbscan,Pentacam,Optical Coherence Tomography(OCT,including time domain-OCT and fourier domain-OCT),corneal endothelium microscope,Lenstar and so on.Among these instruments above,each has its advantages and its disadvantages.However,the measurement of corneal thickness trends is in the development of noncontact,high repeatability and good accuracy.This paper describes the clinical significance of corneal thickness and the progress of the measurements,and all the measurement methods mentioned are analyzed and summarized for ophthalmologists in the clinical reference.