Tunnell Vision - A phenomenon that can render a individual unaware of impending or existing danger. There is an understanding that the individual has experienced or is experiencing some extraordinary sensory input, usually visual, and that the individual's attention is completely "tuned" into this extraordinary event. It can be a "deadly" practice for emergency care providers, for obvious reasons. It is easily avoided, inasmuchas the individual often only needs to be advised that it is occurring.
Note: I searched several dictionaries (via the web) and tried in several different places on the web to retrieve a "professional" definition of Tunnel Vision. I found nothing that was even close. The above definiton is an "aclsman special." It does, however, explain the phenomenon.