In the Shape Flesh ability for Biomancy, it notes that one of the traits a Psyker may give himself with the power is Dark Vision. How does this apply for a Psyker that uses a bionic eye (not both eyes being bionic but only one?)

For the purposes of the power is the Psyker treated as only having one eye when in complete darkness, as his bionic eye (assuming it isn't augmented in any way), cannot see in the dark?

In the same vein that a character with bionic eyes can visually Hallucinate via Psychic Powers, I would rule that Dark Vision affects the brain rather than the eyes themselves. A character with one natural and one bionic eye can still enjoy the full benefit of psychically-granted Dark Vision in my book.

I would assume that it is not just the eye which is altered, but the part of the brain which receives the impulses from the eye. Logically the mechanical eye would be connected to this part of the brain. The enhanced brain would be better equipped to translate the impulses the mechanical eye sends it. Yeah, if you wanted to run around with your good eye closed while the power was on, or you somehow got that eye shot out, I would make an argument that you might not get the bonus, but as long as you have something to shape, the power should work. You could also go with the idea that your good eye is doubly enhanced, compensating for the loss of your normal eye.