This device is also used in order to investigate the corneal surface irregularities and diagnose the corneal ectatic diseases. The imaging technique in this device is computer keratoscope (placido disk-based), which computes the refractive power of different corneal points through analyzing the circles on the surface of the cornea and provides the indices intended by the physician. Considering such technique of the device, the features of the posterior corneal surface cannot be evaluated in this method.