I'm not so sure about that. A small infrared camera and led mounted near the eye can track the eye. Along with tracking, you can also calculate the depth field

I'm not so sure about that. A small infrared camera and led mounted near the eye can track the eye. Along with tracking, you can also calculate the depth field by determining the circumference of the retina. This in turn allows for software-defined focus to be built in on applications. I also see an interesting future for light-depth-field cameras and displays that capture all depths and allow user controlled focus. The question is: can we replay this data format in a single display?