When we read, our eyes don’t move smoothly across the line. Instead, our eyes make a series of jumps and pauses as we read. The small jumps between words or groups of words are called saccades. The brief pause we make while looking at the words is called a fixation A fixation lasts between 1/10 and 3/10 of a second. After a fixation, we move our eyes to the next word or group of words, another saccade. The saccadic movements allow our visual system to scan and will typically move 7-9 characters along the line of text. A large saccade will make the eyes go to the next line of text.
This very precise coordination of jumps and pauses is controlled by our central and peripheral visual systems. Our central vision processes what we’re seeing in clear detail and defines what we’re looking at. Our peripheral, or side vision, simultaneously locates surrounding objects and lets us know where to look. (These two systems are sometimes referred to as the “Where is it?” and “What is it?” systems.) In reading, our central vision processes the word, while our side vision locates the following word and tells us where to aim our eyes next. The integration of these two systems is what allows us to efficiently move our eyes along a line of print without overshooting or undershooting, or mistakenly aiming our eyes at lines above or below. If there is not continuous, fluid, simultaneous integration between these two systems (or too much time on a fixation), reading will be jerky, loss of place will be common, and comprehension will be poor.
At Fitzroy North Eye Centre, we use a Readalyzer to critically analyse a child’s eye movements while reading. The Readalyzer uses infrared to track exactly how the eyes move with reading.