(1) Use a room which is dimly lit. Total darkness is not recommended, as you will be unable to
perform the required adjustments.
If a special room cannot be prepared, use a room without direct sunlight and cover the win-
dows with dark thick curtains.
Furthermore, locate the instrument so that the patient does not face the window.
(2) Connect the power cable to the outlet, if it has not been connected yet.
(3) Turn on the power switch and check whether the pilot lamp is lit.
(4) Set the brightness control switch to the "N" position.
(5) Adjust the instrument to the observer's eye. First, draw out the eyepiece as far as possible, by
turning it counterclockwise to its limit.
Next, place a piece of white paper before the mire plate at the position of the patient's eye, as
shown below, and a blurred black circle image will be seen, as shown below. Turn the eye-
piece slowly in the clockwise direction until the circle image is seen distinctly as a double cir-
(6) Set 0° or 180° of the protractor scale to the black-colored horizontal index.