VERIS
™
Service Manual
EMS & FMS Stimulators
VG-119-D / 21-Jan-2017
Page 11 of 16
10.
Stimulus Grid Calibration (FMS Stimulators only)
The retina does not reflect enough light to make it possible to see the stimulus in the IR fundus
image
.
To make it possible for the operator to monitor where the subject is fixating on the multifocal
stimulus array, Veris™ overlays an outline of the stimulus grid on the fundus image. This grid must
be calibrated to match the actual stimulus. This is achieved using a model eye (Grid Calibrator) with
a highly reflective fundus using the following procedure:
1.
With a test subject folder open, select the protocol containing the words ‘for grid calibration’.
from the "FMS Microdisplay" Analysis Settings folder.
2.
Open a recording window.
3.
Place the Grid Calibrator on the FMS
front lens.
4.
Turn off IR illumination with the toggle
switch at the back of the black
microdisplay tube.
5.
Select the fundus camera by toggling the up or down arrow keys of the computer keyboard.
6.
Double-click on the fundus image in the window to open the camera controls.
7.
Adjust the image brightness by means of and contrast controls and by rotating the Grid Calibrator
as necessary. Fluctuations of image brightness are normal. If you can still not see the stimulus
well enough, you may open the lens aperture. To do so, move the camera back out of the FMS IV
housing using the focusing knob until the black aperture lever is accessible.
8.
Focus the video image
9.
Open the "Stimulus" tab of the camera
control window and adjust the size and
position of the grid to match the stimulus as
closely as possible. (Holding the "
shift
"
key down on the keyboard while clicking
on the size and position controls produces
larger changes.)
10.
Click OK to exit from the controls dialog,
then exit from the recording window when
the grid matches the stimulus as closely as
possible. Contact EDI if a satisfactory
match cannot be achieved.
11.
Reposition the CCD camera aperture to the
position you normally use for fundus monitoring and switch the IR fundus illumination back on.
This calibration will be correct for any multifocal stimulus array and for any refractive
correction.
EDI recommends repeating this procedure every 3-4 months or whenever a new version of the
software has been installed.
