MEASURING THE 
                  TEAR FILM 
              BREAK-UP TIME

Immediately following the instillation of fluorescein the B.U.T. should be measured.  The room lights should be out and the filters in place on the biomicroscope.  A wide light beam should be used.  The patient is asked to blink 3 or 4 times and then to look straight ahead and not blink.  The time (in seconds) from the last blink until a dark spot or streak develops in the tear film is the B.U.T.  Do not hold the lids open.