vertical and horizontal scanning mirrors 4 and 4 39 by means of sawtooth wave generators 42 and 42 39 and vertical and horizontal scanning mirror drive circuits 43 and 43 39 the sawtooth wave generators 42 and 42 39 each produce the type of signal shown in fig4 a and 4b for the scanning of the laser beam in the drawing x1 indicates the starting point of the measurement and x2 the completion of the measurement if horizontal frequency is h f and vertical frequency is v f and the number of vertical scans is n then h f v f n the vertical and horizontal scanning mirrors 4 and 4 39 are scanned in accordance with the signal waveforms causing the laser beam to perform scanning with measurement point p at the center of the scan fig5 shows the actual scanning state as seen from the laser beam projector in order to remove noise components formed by light reflections in the eye and efficiently receive signals derived from the scattered light the width of the vertical scan is set smaller than the vertical width of the slit 26a thus the photomultiplier 27 receives the incident scattered laser light via the slit 26a detects the intensity of the light that has been scattered by floating particles in the anterior chamber 11a and converts this into a corresponding series of pulses which are counted by a counter 40 as number of pulses per unit time period and the count values are then.