According to the College of Optometrists in Vision Development (COVD), one in four children struggle with reading and learning unnecessarily because of undiagnosed vision problems, and approximately 60% of problem learners have undiagnosed vision problems contributing to their difficulties (1).
So what does a child need visually to be able to read well?
- Clear vision up close. Pretty obvious, right? It’s more difficult to discover problems here than it would seem. Children who can’t see well at near very often fall through the cracks during vision screenings, because many will read the distance chart and pass easily. Beyond just making reading and near tasks difficult, high amounts of farsightedness (hyperopia) in one or both eyes, if left uncorrected, can prevent the visual system from developing to its full potential (amblyopia). For more information about refractive errors and ambylopia, check out the back-to-school post. Problems with the focusing (accomodative) system of the eye can also make vision up close unclear.
- Single vision up close. Eye teaming refers to the ability of both eyes to work together. Convergence is the ability to move both eyes in when looking up close. Problems with convergence (either insufficiency or excess) can cause difficulty when reading. Double vision can result if one eye is aimed in a different direction than the other, causing the brain to receive two different images that it cannot fuse. To avoid seeing double, the visual system may suppress, or “turn off” an eye, or use the focusing system to compensate. As we will discuss below, these ways of coping often cause eyestrain, blur, headaches, and fatigue, and children are not likely to read for long periods of time if this is what they’re dealing with just to see the words on the page.
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| Image from Wow Vision Blog |
- Accurate and efficient eye movement. As we discussed in last year’s vision and learning post, the act of reading involves a series of eye movements called saccades and fixations. Saccades are the eye movements that allow us to quickly redirect our line of sight from one location to another. When reading, saccades allow us to move through a line of text. The normal reader averages about 7-9 letter spaces per saccade. Fixations occur when the eye is relatively still, allowing us to maintain a steady gaze. Regressions are eye movements in the right-to-left direction that occur when we reread a word or section. They occur 10-15% of the time in skilled readers. Less skilled readers typically have longer fixations, shorter saccades, and make more regressions than more skilled readers (2). When these ocular motor skills are deficient, it can lead to one losing their place when reading, skipping words, and reading slowly.
- Comfortable vision. Eyestrain, blur, headaches, and fatigue are common symptoms of problems with focusing and/or eye teaming. Any of the aforementioned conditions can cause reading and schoolwork to be uncomfortable, which often causes children to become disengaged and inattentive.
- Visual-perceptual skills. Visual perception is how we process and understand what we see, and it happens at the level of the brain. We don’t see with our eyes; we see through them. Problems with visual memory (the ability to recall what is seen), visual spatial skills (the ability to understand directional concepts and organize visual information), and visual discrimination (the ability to identify features of and discriminate between different letters, numbers, etc) can negatively affect a child’s ability to read and learn. A 2012 study found a correlation between visual spatial skills in preschoolers and their future reading skills (3). Integration between the senses is critical as well, as visual-motor and visual-auditory integration also affect learning.
It is important to note that vision is more than 20/20! Reading involves the integration of so many visual skills, and it is a visually demanding task. When the visual demands of a task exceed a child’s visual skills, symptoms/difficulties arise. In a great TEDx Talk on the subject (watch here), Dr. McCrodan likened the visual system to an engine: “If it is really inefficient, you’re going to burn out of gas a lot faster.” Children often don’t say anything because they don’t know any differently. If your child is struggling at school, see your optometrist to have their visual skills evaluated. If your optometrist does not perform these types of evaluations, they can certainly point you to an optometrist that does. You can also visit www.covd.org to find one in your area.
CliffsNotes: Vision is more than 20/20! Reading involves the integration of many visual skills.
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