Nagel color vision microscopy, a color vision microscope is a spectroscopic instrument designed based on the principle that red light and green light are properly mixed to form yellow light. Therefore, in clinical practice, Nagel color vision microscopy is commonly used to examine patients with green color blindness. 1.The examinee sits in front of the instrument and gazes from the observation hole, a circular disc is visible, the upper half is red or green and the lower half is yellow. 2, the inspector will adjust the right side of the yellow light brightness of the monochromatic knob to 12.5 scale, asked the examined person to rotate the left side of the mixed color knob, until the upper and lower halves of the circle color and brightness are identical. Note down the reading, the normal equalization point is about 70 scale. 3, the inspector will mix the color knob to 0 degrees, and asked the subject to rotate the monochrome knob. Each increase in the mixing knob 10 ° inspector rotate the monochrome knob until equal, record its equal point, re-test three times, take its average. 4, the results will be recorded in the special table, draw the parity curve.