10 How the C-Quant works
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Instruction Manual C-Quant ( G/80000/1007/en)
These two fields are shown in black in the diagram below.
.
Fig. 10-1: Stimulus field
Now the outer ring starts to flicker.
The phase when the ring is on is referred to as the "on-phase" and the phase when it is
off is referred to as the "off-phase".
In the on-phase the ring of the straylight source is projected onto the retina.
However, some of the light is scattered by the lens and other parts of the eye and is thus
projected on the part of the retina onto which the test field projects (fovea).
On-phase
Off-phase
As a result of the light scatter the patient thus sees the test field flicker synchronously
with the straylight source even though it is actually dark.
Since only a small fraction of the light emitted by the straylight source is actually scat-
tered the test field appears to flicker gray.
straylight source (outer ring)
central test field
straylight
