OCULUS Easygraph 70620 Instruction Manual page 22

Page 22
Provided that the Easygraph is nearly in releasing
position, the Easygraph then automatically measures
This graphical display gives a side view and a top
view of the measuring process and also shows the
direction in which the unit can be moved in order to
arrive at releasing position (fine adjustment).
Measurement is carried out automatically if the
Easygraph is in releasing position. For this, however,
it is first necessary to give the go-ahead for
measurement.
Before this go-ahead for measurement is given, the
patient should be asked to open his eye wide so that
as large a region of the corneal surface will be
measured as possible.
The go-ahead is carried out by pressing the space
bar of the PC keyboard.
Note: ⇒ If the measurement system does not
release (for example in the presence of a very
pronounced keratoconus), measurement can be
forced by pressing the RETURN key on the PC
keyboard.
After measurement has been activated the image is
transferred in digital form to the PC and displayed.
Then the processing
automatically.
Instruction Manual Easygraph
of the image begins
the distance to the patient's eye and shows it
graphically next to the camera image.
Now the geometric surface of the cornea and the
local radii of curvature are calculated from the
reflection image of the Placido system, stored
automatically, and presented on the screen in the
form of an overview display.
Note: ⇒ The user can first familiarize himself with
this procedure by carrying out the measuring
process a few times with the glass globe which is
delivered with the unit.
Note: ⇒ The patient's nose and forehead may cast
shadows on the ring system. These areas are then
inaccessible for measurement, making interpolation
necessary (black dots or white areas in the color
topographic image, see also 7.5.2.2 page 25).
Overshadowing of the ring system can be minimized
by placing the patient's head in the chin-and-
forehead rest in such a way that his nose is as far
away from the Easygraph as possible (turn head,
measure more from the side). However, it is
essential that the patient still keeps his eyes fixed on
the fixation LED.