On the Scholl website, if you watch the day in the life of a pod student video, it talks about and shows footage of the Ghana trip. I just watched it about two weeks ago. I believe it said that students are there for a month. So, maybe that is an option instead of taking your "vacation" month during externships. Looks awesome doesn't it?
My best friend is an Optometrist. When she was in school I accompanied her and some classmates on a mission to Honduras. It was incredible! I would do it every year if I could. As a team (there were about 75 in all) we saw over 1,000 patients per day.
I really hope that once I am practicing, I will do something similar yearly. And it doesn't have to only be out of the country. My Mom's family is from super rural appalachia...I could see setting something up to go down there and provide treatment for people.