Note:Please choose a well-lit environment.Keep the eyes of the two people at the same level when measuring, which will make the measurement more accurate.Do not move the machine while measuring, otherwise it will cause a large error.When measuring the distance between the eyes, keep the machine still, and check whether the left and right eyes are facing the vertical line in the field of view at the same time.Specification:Set auto shutdown time：0.5-3.0minSet aperture brightness：5.0-0.5Set accuracy：±0.5 - 0.1mmPower Supply: AA batteries (Not Included)Dimensions: 260 x 230 x 100mmNet Weight: 1kgPackage Includes: 1 X Digital PD MeterUsing steps：1. Boot:Install two of AA battery, press the power button（Main key）.2. Basic settings:According to the measurement needs, adjust the VD and select binocular/monocular measurement.3. Start measuring:Place the machine between the tester and the subject as shown above, with the machine facing up.Keep the machine level, the eyes of the two are at the same level, and the metal frame is placed on the forehead of the person being tested, so that the machine is facing the nose.The subject is visually in front, and the examiner observes from the front window, and moves the left and right sliders so that the vertical line faces the center of the pupil.Do not move the machine during the test, repeat the calibration, do not move the slider after the alignment.4. Reading:Remove the distance meter and read the data. The test procedure should be repeated at least 3 times and can be combined with monocular and binocular measurements t