Loss of vision after pituitary tumor removal surgery

My dad, 59 had a brain surgey 5 months ago (removal of pituitary tumor) and immediately after the surgery we learnt that he lossed his vision in both eyes. Prior to the surgery he was able to see from his right eye as the tumor was pressing against the optic nerve of his left eye. The doctor was confident and said that he will regain his vision slowly but surely. Immediately after the surgery he was not able to even see light but now he can see shadows and shapes and at times he can see a few colors. He is depressed and cannot get about. Has anyone experienced anything of this sort? what might have caused this to happen? One eye doctor was of the opinion it could be due to a clot in the optic chiasm. Since he can see some objects there is no reason to believe that his optic nerves are damaged?