10 How the C-Quant works
Instruction Manual C-Quant ( G/80000/1007/en) 29 / 56
To determine the amount of light that is scattered by the patient’s eye the test field is now
made to flicker itself, but counter-phase to the straylight source: When the straylight
source is off the test field is on and vice versa.
Now the test field appears gray both in the on-phase and in the off-phase.
On-phase
Off-phase
Now the brightness of the test field is adjusted until the patient no longer sees any flicker.
This yields his or her straylight value.
10.2 Compensation comparison method
Determining the exact straylight value by means of direct compensation has proven dif-
ficult in practice because many patients are unable to tell when the test field no longer
flickers.
For this reason the compensation comparison method was developed.
The stimulus field with this method is similar to that used with the direct compensation
method, except that the test field is divided in two.
straylight
compensation
light
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