What Causes Blindness In Left Eye With Occasional Flashes Of Light?

Hello My husband has not been able to see out of his left eye for a few days now. He says that it is completely black. He says sometimes he can see little flashes of light when he blinks but that is it. This happened to him a long time ago and the doctor could not find anything wrong. He is also having other symptoms such as congestion in the nose and the whole side of his face (same side as the eye) is hurting and feels like pressure. Do you have any idea what might be causing this?