A serious issue that I’m facing is the lack of control over rhythmical timing when playing using the eyes. The research on the subject also points towards a maybe non-solvable problem

What is evident is that eye tapping differs from finger tapping and drumming in that subjects are more inaccurate [10]. The mean error in this study was 137 msec which is a quite noticeable error when beating out a rhythm. If implement- ing an eye controlled instrument one should be prepared for that the rhythmic accuracy of the users of your instrument might be quite low.

Eye Tapping : How to Beat Out an Accurate Rhythm using Eye Movements (Rasmus Bååth, Thomas Strandberg, Christian Balkenius), In Proceedings of the International Conference on New Interfaces for Musical Expression, 2011.

In the two videos below I have tried to first play a simple musical sequence with the mouse (which is not that easy), and afterwards with the eyes. It is worth noting that I don’t play a single wrong note in either of the two examples, however, sticking to the beat of the metronome is almost impossible for me when playing with the eyes (although I rehearsed it several times beforehand).