More about eye movements

 When we read, our eyes move through the text with small bursts of movements, not a single sweeping movement – even though it might feel like a single movement to us. Put simply, our eyes do three things while reading: fixations, progressive saccades and regressive saccades. Fixations are when the eyes are still and take in information. Progressive saccades are movements forward from one fixation point in the text to the next. Regressive saccades are when the gaze returns to an earlier part of the text.

In the analysis of eye movements during reading, eye movements are first divided into fixations and saccades. The fixations and saccades are then subdivided, depending on whether they are progressive or regressive with regard to the reading direction. Numerous parameters are then calculated for each single movement. These parameters describe characteristics of the movement over time. 

In or assessment of reading ability, these calculations are compared with a statistical model for the grade at the time of testing. The model is based on analyses of eye movements in a large number of students that also include traditional tests for decoding and phonological awareness. This means that the model can make a correct assessment of whether there is a risk of reading and writing difficulties based on a brief recording of eye movements. All parameters are used in the assessment, and it is their mutual relationship that leads to a result. It is therefore not possible to explain the result based on a single parameter – just like the models used, you need  to take a comprehensive view.