Writing image (onto retina) is quite feasible, it's reading that is a problem now. A while back there was an experiment conducted to 'read' image in a person's mind, but what they had really done was mapping a certain image/video clip to a certain expression of the brain's activity. It can't read arbitrary image yet.

http://newscenter.berkeley.edu/2011/09/22/brain-movies/

Correction: we can read arbitrary images, but so far only with cat's brain:

http://www.youtube.com/watch?v=FLb9EIiSyG8