Before the brain can make meaning from text, the eyes must deliver it clearly, steadily, and as a team. Here’s how that system works—and what happens when it doesn’t.
Reading begins as a visual task: the eyes must focus, move accurately across a line, and work together to send the brain a clean image of the print. When any part of that system falls short, students can struggle in ways that look like inattention, low ability, or reluctance. Below is an overview of the visual system and reading.
Visual Acuity
Can you see clearly?
Visual acuity relates to how clearly we can see close-up as well as at a distance. If a person has 20/20 vision it means that this person can see clearly at 20 feet what should normally be seen at that distance. If a person has 20/50 vision, on the other hand, it means that this person can see at 20 feet what a person with normal vision can see at 50 feet.
Vision screenings conducted in schools typically focus on visual acuity measures, using the Snellen chart (see above picture) to determine whether a child has satisfactory eyesight for the classroom (Zaba, 2011). Such screenings prioritize distance vision, when in fact the majority of schoolwork involves near vision.
20/20 vision does not mean that we have perfect vision, it simply means that we can see clearly at that distance. While some people may be able to see well at a certain distance, they may struggle to focus on nearer objects. This condition is called hyperopia (farsightedness). People who are able to see clearly close up but struggle to bring objects at a distance into clear focus are experiencing myopia (nearsightedness) (American Optometric Association, 2022).
It is important to note that people can experience focusing problems even without being nearsighted or farsighted. Measuring accommodation is also important because it is a critical skill that is required to establish and sustain target clarity at all distances. Symptoms of a possible accommodation problem include: short attention span, reduced reading comprehension, task avoidance, excessive time completing assignments, daydreaming, fatigue, headaches, and blurred print (College of Optometrists in Vision Development, 2017).
Eye-Movement Control and Vergence/Binocularity
Are your eyes working as an efficient team?
Efficient readers move their eyes reasonably sequentially along lines of print, ideally taking in words as units without much visual wandering or excessive eye movements and fixations (eye stops).
If students have poor text navigation skills, making multiple fixations per word to capture visual impressions in an attempt to unlock the meaning of words, they will experience reading as a very labor-intensive and exhausting process.
For example, in the following passage, the red dots indicate that the reader often made 2 to 4 fixations to take in invididual words. Efficient readers, on the other hand, typically take in between 1 to 1.5 words per fixation.
Text Navigation Skills
When readers extensively re-fixate on the same words as they read, passage comprehension will be greatly diminished as excessive attention is dedicated to the mechanics of reading rather than information processing and understanding. These students typically will not enjoy reading and avoid it whenever possible.
The ability to align eyes accurately on a target to fuse images from both eyes into a single image is essential to be able to effectively locate targets and achieve depth perception (College of Optometrists in Vision and Development, 2022). If students struggle to converge their eyes at the right depth, reading will become a very confusing and exhausting task.
For example, in the following passage, the red and blue dots indicate the fixation positions of the reader’s left and right eye. As you can see, the eyes often did not meet at the same fixation points or land on the lines of text. Larger circles indicate that the reader spent more time associating meaning with the visual impressions. Efficient readers, on the other hand, typically display greater alignment between their eyes both in regard to fixation position and duration time.
Aligned Eyes and Depth Perception
Students who exhibit the reading pattern displayed above typically experience one or more of the following symptoms: words moving on the page, skipping words, creating (i.e., seeing) words that do not match the print, complaining about headaches and fatigue, poor handwriting, motion sickness, closing or covering one eye, being inattentive, clumsy, or feeling excessively challenged engaging in sports that require aim and eye-hand coordination (College of Optometrists in Vision and Development, 2022).
Visual Processing
Can you understand what you are looking at?
As part of the meaning-making process, we transform visual images into mental images. To achieve this we involve our memory, our visualization capabilities, and connect background knowledge.
However, distorting the visual input phase can greatly hinder, or even prevent, the meaning-making process, regardless of a student’s adequate intellectual capabilities.
Limitations of acuity impact visual processing. This acuity peaks in the fovea (the central 2° of a fixation). Vision loses clarity in the parafovea (which extends out to 5° on either side of fixation) and degrades even further in the perifovea and periphery (the regions beyond the parafovea) (Iwasaki & Inomata, 1986; Rayner, 1998). This means that we end up with an average perceptual span (i.e., the number of letters a person can perceive and process during a single eye stop (fixation)) that includes about four to six letters to the left of the fixation point and about eight to twelve letters to the right. This is the extent to which we can see crisply. Beyond this area, we are relying on word shape information.
The average perceptual span of beginning readers and of most people who struggle with reading is smaller than the span of efficient readers (Rayner, 1986). This means that efficient readers perceive larger word impressions per fixation, which contributes to automaticity in word recognition and paves the way for more efficient text navigation and streamlined visual processing.
Perceptual Span of Efficient and Inefficient Readers
