There are many new instruments used to measure biometric measurements in recent years, such as intraocular len-master(IOL Master), ultrasound biomicroscope(UBM), Pentacam, optical coherence tomography(OCT), Orbscan, Lenstar LS900, Galilei, specular microscope, confocal microscope, and so on. Among these instruments mentioned above, the principle and clinical application are different. This article will review the principle, usage, clinical application of the Lenstar which is a new optical low coherence reflectometry device.