Topcon OM-4, Instruction Manual, Page: 19 / 38

17
OPERATION PROCEDURES
When the readings of the horizontal and vertical scales are identical, it will not be necessary to
determine the axis. The test ball is supplied for the purpose of practicing measurements as
well as for checking the accuracy of the instrument which should be undertaken from time to
time.
The horizontal knob, vertical knob and axis rotating handle can be manipulated with one hand
after a little practice. Operations will be even simpler. In this case, if the auxiliary knob is
attached to the horizontal knob, in the case of a right-handed person, and to the vertical knob,
in the case of a left-handed person, it will make operations much easier.
MEASUREMENT OF THE RADIUS OF CURVATURE OF THE CORNEA
(1) Positioning the patient
Place a suitable quantity of papers on the chinrest and fix them in place, with the two chinrest
paper pins, as in step (4) of "ASSEMBLY PROCEDURE" (see pg. 12).
Have the patient sit in a relaxed position in front of the instrument. Next, move the adjustable
instrument table up or down (ex. AIT-10B, an optional accessory) to adjust the patient's eye
height point outline according to the canthus marker of the chinrest. Adjust the chinrest
adjuster accordingly. Instruct the patient to place his/her chin on the chinrest and his/her fore-
head against the forehead rest.
(2) Positioning the instrument in front of the patient
The same operations undertaken for positioning the instrument before the test ball should be
undertaken now, not for the test ball but for the patient's eye.
In other words, position the observer's eye so that the leveling pin, black-colored horizontal
index and patient's eye are all on the same line of sight, using the joystick if necessary, for this
purpose.