Hi!
You may try taking a look at this 3rd party project
http://iris.xcessity.at/
If your want to code such functionality yourself you should start with these samples:
– TobiiEyeXSdk-DotNet-1.7.480.zip\source\WpfSamples\ActivatableElements & SDK documentation
– TobiiEyeXSdk-Cpp-1.7.480.zip\samples\ActivatableButtons if you prefer C++
I also want to mention that we don’t recommend doing completely hands-free interactions in most of the cases except accessibility applications. Preferred way would be to activate elements by clicking a button on a mouse/keyboard/gamepad