Hidden Oblique Checker This instrument is mainly used to check the degree of the secret oblique prism of the human eye, (adding a single prism can expand the inspection range) is one of the instruments for diagnosing abnormal eye position. Inspection range: 020 ( is the degree of the prism), the value of each division is 1. Operation method: Hold the handle 1 of the instrument with your hand, align the index mark on the rotating prism 2 with the "0" mark on the reading ring 3 (hereinafter referred to as zero), and look at the front 3~5 meters at the same time. The light source of the bulb (can be used as the light source of ordinary flashlight). Then lean on the end face of the Markov frame 4 with one eye, observe the point light source through the instrument, and observe the point light source directly with the other eye. At this time, one sees a bright red ray, and the other sees a light spot of the light source. If the light does not pass through the light spot, it means that there is a cryptic skew in both eyes. At this time, turn the small handwheel 5 until the bright red light passes through the light spot, and then read on the reading ring. The value read is the degree of the cryptic prism to be checked. After resetting to zero, place the instrument in front of the left (right) eyes according to the vertical position of the Markov stripe slot. At this time, the left (right) eye sees a horizontal bright red light, and the right (left) eye sees the light source. point. The light spot is located above (below) the bright red light, that is, it is cryptic on the left eye; otherwise, it is cryptic on the right eye (see Figure 2). Turn the small handwheel 5 so that the bright red light passes through the light spot of the light source. Then read on the reading ring.