Yes, I also went on Goenka retreat recently (last November) and I help myself to concentrate on a particular body area by focusing my eyes all the time!!! I didn't know that it was a problem! I never told about it to assistant teachers. And when I remove my visual focus it feels like my concentration weakens somewhat, so I actually intentionally maintained the focus. It never really bothered me, though a couple of times I had thought that it might be bad for the eyes to be focused on one spot for prolonged periods of time (of course I have my eyes closed, and it's more mental than visual, but eyes muscles are working anyway). When I have full body awareness, I usually still have my innner visual focus on the area of the nostrils. So, do I really have to break this habit? and what should I do with my eyes instead? wow, I didn't know I had a bad habit to break