Canon EOS R3 Advanced User's Manual page 84

Using Eye Control for AF
Caution
Always use eye control under the same eyewear conditions as when you
performed calibration (such as with or without glasses or contact lenses).
Note
Also read General eye control precautions
Menu settings
1.
Select [ : Eye control
2.
Select [Eye control
and Enhancing eye control
].
].
84
accuracy.