Next, cover the other eye with the occluder so the patient can not see with it.
Once the height of the instrument and patient's eye have been properly adjusted in the above
manner, use the joystick to produce the mire images.
In case the image is dark and hard to see, turn the brightness control switch to the "H" posi-
tion. However, do not make the image too bright, as it will not only tire the patient but also will
shorten the lamp life.
For the purpose of making measurements easier and for obtaining accurate results, the
patient should be warned against moving his/her face. The patient should look at the pupil
image reflected in the reflection mirror directly in front, without shifting the eye. The instrument
will be set to the correct distance when the double images, in the center of field of view, are
unified into a single image by turning the joystick.
(a) When there is corneal astigmatism
Tu rn t h e a xis ro ta t i n g h a n d l e , w h e n c o r n e a l a s t i g m a t i s m e x i ts . T h e " ---|---" m a r k o f t h e t o p
mire image and the "--|--" mark of the center mire image will be seen in the displaced posi-
8.5 8.6 8.7
8.5 8.6 8.7