Ricoh PENTAX K-3 Mark III Faq page 11

You can set the camera operation when the eye sensor detects the user's eye in [Eye sensor] of
the C4 Menu.
Link Monitor
Display.
AE with Eye
Sensor.
Detection
Sensitivity
Turn off the monitor backlight when the eye sensor detects th
e user's eye.
Starts metering when the eye sensor detects the User's eye.
Sets the eye sensor detection sensitivity.
- 11 -