I'm not sure how being a "full-time student" differs from bearing a "full course-load." Nonetheless, in response to the spirit of your query, I think most schools just want to see you can take several courses simultaneously, and do well in all of them. I believe they'd consider a candidate who took a class or two, per semester, to make room for working/life/family/etc., but they're likely to favor the applicant who's shown he or she has the capacity to undertake a rigorous curriculum (as that is what an O.D. program will present).