Accurate eye movement control, otherwise known as tracking, is required to follow a line of print and is especially important in reading.
Children with tracking problems tend to be slower readers. They often lose their place, miss and skip words and lines, have poor fluency, have difficulty copying from the blackboard, will often report that words appear to move on the page when reading, and tend to have difficulty comprehending because of their difficulty moving their eyes accurately. Many are forced to use their finger to follow the line because their eyes can’t.
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. After a fixation, we move our eyes to the next word or group of words another saccade.
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, reading will be jerky, loss of place will be common, and comprehension will be poor.
How Can Poor Tracking Control Affect Reading Skills?
Children with poor eye movement or tracking control tend to make a greater number of inaccurate saccadic eye movements when reading. When we perform a saccade, new information cannot be processed because the eyes are moving so quickly across the stable visual stimulus that only a blur is perceived. This phenomenon is known as saccadic suppression. Therefore, if a child is forced to make more saccades than the average child their age when reading, they will have greater periods where they are not processing new information, which results in a slower reading rate. Their reading rate will slow even further considering that it takes longer to initiate saccades in the first place and the fact that their saccades are also more inaccurate.
Can Poor Tracking Control Be Fixed?
Poor tracking can be remediated through vision therapy. If vision therapy is required it usually consists of six in-office visits spaced one week apart, along with home-based therapy between these visits. Treatment duration will depend on the particular patient’s condition.