Okay, thanks! I guess what confuses me is that recently they added the criterion that the stall has to be present for the entire movie in order for the blood vessel to be considered as stalled. I guess what they mean by that is that the stall has to be visible for the entire movie. Well, here is a case where the stall is only visible immediately before it gets washed out by the luminescence. If the stall has been washed out by the luminescence, how do we know that it is still present?
For me, the assumption here is that the stall is still present even though it's not visible to the eye. I don't understand how we can know this just based upon what is visible. The expert knows based on some information, or knowledge that the stall is still there, but how are we supposed to know that? It just seems to me that this is one occasion, and I do believe there are many others, when the expert makes a determination based on something other than what is visible to the eye.