temporary blindness in the right eye

My friend had an episode of temporary blindness in his right eye for about 3 to 5 min. He had been suffering neck and back pain for several weeks that also occasionally caused pain in his right eye. His neck pain was causing him migraines. Since his work requires at least 12hours on the computer, we thought it was just muscle issues and bad back pain but since his episode we've been very worried. He is going to get an MRA and MRI tomorrow. Any suggestions as to what may have caused his temporary blindness?

Thank you