PLUSOPTIX PowerRef 3 Instruction Manual page 15

Step 4: Press "Start camera" and be sure that the pupils will be detected continuously.
If the pupils are not found continuously please make sure the pupils are > 4mm
and no eye lit or eye shade will cover the eyes. In some cases it can be helpful
to deactivate the automatic brightness. And try to find a good regulation with
the manual brightness control.
Manual brightness control
Automatic Brightness
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