Foveal and Parafoveal Reading
Human eyes do not move continuously along a line of text while reading; instead, they jump across the line in rapid movements (known as saccades), between these saccades the eyes stop for a fraction of seconds (fixations).
A diagram showing the saccades (jumps) and fixations (pauses) during the reading process.
In the retina, the fovea is a central pit composed of tightly packed cones in the eye which are responsible for the sharp central vision also known as foveal vision. The distance the eye moves in each saccade is between 1–20 characters with the average being 7–9 characters. The saccades last for 20–40ms, and during this time the vision is suppressed, no new information is acquired.
A diagram showing the foveal, parafoveal, and peripheral regions while reading a line of text. The dotted line in the middle represents the location of fixation. Diagram based on Parafoveal processing in reading, https://link. springer.com/article/10.3758/s13414–011–0219–2
According to studies along with the foveal area, the parafoveal area also has a vital role in continuous reading. O’Regan in his study stated that the next word influences the length of saccades: longer words result in longer saccades and short words have short saccades. Thus it can be said that the parafoveal region plays a critical role in continuous reading and should be taken into account while designing typefaces to be used in AR applications for longer text setting.
 K. O’Regan, Moment to Moment Control of Eye Saccades as a Function of Textual Parameters in Reading, cited in A. Kolers, M.E. Wrolstad & H. Bouma, (eds), Processing of Visible Language, New York: Plenum Press, 1979, pp. 49–60