FAQ: How can I calculate saccadic reaction times (RTs)?
#1
There are two methods to extract saccadic reaction times:
  1. During the Experiment

    If reaction times (RT) are required during the experiment (for example, to provide feedback based on saccade RT), you can compute the RT by updating a variable with a difference calculation between when the stimulus was displayed and the time the saccade trigger fired, as demonstrated in the image below. Please note that these time values will be relative to the Display PC clock, which starts at the beginning of the experiment. See How can I accurately keep track of reaction times (RT) for participant responses? for more details.

       

  2. After Data is Collected

    If reaction times are not required during the experiment, they can be extracted after data collection based on the EDF file time in Data Viewer. The EDF file times are based on the Host PC clock which starts when the EyeLink program began for that session. 
The results from these two approaches should be fairly close to each other, if not identical for the same events.