Howling:An eye watching River?

In the episode Flesh and Stone, there appears to be an eye watching River Song from one of the ships monitors. The camera focuses on it a lot, and it is the only thing moving on the screen. It also emits some kind of static noise.

Interestingly, it moves in much the same way the Valtraxi eye moved when searching for Prisoner Zero. River Song has also been proved to be a prisoner.