Sorry, as someone who has worked in VR and including with eye tracking for over 20 years, no. Eye or gaze tracking is definitely *not* an input device and should never be used as one.

At least not in the sense of using it as some sort of conscious, user controlled input. Using it to *passively monitor* where and what the user is looking at is fine and useful, though, but maybe less so than many think.

The reason for this is simple - humans don't consciously control eye movement to the same degree as e.g. their limbs. A lot of eye movement is completely automatic.

And even the little that we can consciously control would get extremely fatiguing fast - imagine not being able to move your gaze even a millimeter while driving a car without risking a crash! We have made such experiment around 2004 where the user was asked to guide a character walking on a projection screen (not HMD) by gaze. Most people got a horrible headache within few minutes and it was very uncomfortable.

Another aspect is that eye tracking isn't magic. There is literally an infrared camera looking at your eye from a close distance. This camera has a finite resolution and the eyeball/iris moves relatively little.

With the target the user is actually looking at being several meters away (whether in reality or VR makes no difference here), you could at best identify large objects or some sort of zones where the user is likely to be looking. Beyond 2-3 meters the errors grow fast because the same eye movement corresponds to much a larger displacement the farther the target is (think shining a torch at a distant wall - little hand movement makes it move a lot).

Oh and it still totally ignores the last detail - human eye is not a camera or gun that you aim at something and what the red crosshair aligns with is what the user is looking at. That only means that the thing is in the field of view but the user could be focused on something totally different in the same FOV.

Ever seen those experiments where you are asked to follow some ball or card or count how many objects of some kind are in the scene - and at the end you get asked whether you have noticed the gorilla walking through the stage. Most people won't, yet it was directly in their field of view. Our brain is a large part of the visual perception and yet we have no way to know what it is really "looking at".

So unless we are talking special cases like accessibility solutions for people with disabilities, eye tracking certainly isn't a good candidate for an input device.

And even for things like foveated rendering its utility is a disputable - the complexity, added latency and computational requirements may often outweigh the benefits. Foveated rendering can be done with a fixed, untracked FOV - not ideal but often good enough.

Where I could see it being genuinely useful for VR is eye contact between avatars. That's a big problem that this could solve. However, whether it would justify the extra cost of the headset, the required extra user discomfort (calibration, extra setup required for good results, etc.) I doubt.

Then there are obviously research and professional uses (e.g. tracking attention of a trainee during an instruction session) but those are niche application cases.

And, well, lets not get into the "big brother" stuff where one will be tracked, profiled and evaluated on whether or not they looked at ads, signs or even a cute girl/boy passing by. Companies like Facebook (err Meta) being involved with this should give anyone a pause.