Blindsight is a syndrome, which can have a number of organic causes, in which the sufferer has no experience of some aspect of visual perception but whose behaviour is such that it is evident that the visual information has been processed by some area of the brain - the person who can navigate obstacles whilst reporting that they cannot see them for example. However, it is not really an all or nothing kind of thing - we all, all the time, process visual information of which we have no conscious experience of perceiving. I'm not sure what the nature of the link with LCD refresh rates is though
