When Sossan returns to Iran to do charity cases, he is usually there for a two-week window. During that time he sees 12-14 patients, does their complex surgeries and is there for the first all-important phase of healing.

"Two weeks is the most I can be away from home," he said. "Therefore, they try to book most of my cases at the front end so I can do their follow-up treatments. They don't give me the easy ones; they give me the ones that no one else wants to do."