vision + learning, the sequel

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. 

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.

Additional Recommended Resources:

• TEDx Talk: Overlooking our vision
• Eye Can Learn
• COVD: Vision and Learning
• AOA: Reading and Vision
• Vision and Learning

back-to-school eye exams

For many parents, the next few weeks will be filled with orientations, school supply lists, sports physicals, and immunizations.  If you are in that boat, be sure to include a visit to your eye doctor to have your child's eyes examined before starting the school year.  Experts estimate that as much as 80% of learning occurs through the visual system (1), so give your child every possible opportunity to succeed in school.  Learning, particularly in the form of reading, requires a combination of many visual skills.  There is far more to vision than just seeing 20/20.  

Vision screenings at the pediatrician's office and at school, though helpful in flagging some potential problems, usually only assess one or two aspects of vision.  Screenings are limited and non-diagnostic, so they are not a substitute for a comprehensive eye exam.  I regularly see kids who pass school screenings but have vision problems that need to be addressed.  Some states actually require a comprehensive eye exam before entering kindergarten, which is a fantastic idea.  The visual system is not fully developed in young children, and equal input from both eyes is necessary for proper development.  The earlier problems are detected, the better the chance of treatment being successful.  The American Optometric Association (AOA) recommends an eye exam at 6 months old, 3 years old, and again before entering first grade.  While in school, a child/teen should have an eye exam at least every 2 years if no issues exist, or yearly if he/she wears glasses or contact lenses.  Depending on the child and the condition, your eye doctor may recommend more frequent examinations.  

Some common signs and symptoms for parents and teachers to keep an eye out for:

• squinting
• eye(s) turning in or out
• sitting close to the TV 
• holding books close to the face
• complaining of seeing double
• complaining of headaches
• tilting head 
• avoiding reading and/or reading slowly
• losing place when reading and/or skipping words

While some children will have symptoms and signs that parents and/or teachers can pick up on, it is not uncommon to find children with issues that do not report any symptoms at all.  That is why the objective tests done during a comprehensive eye exam are so important for young children.    

According to the American Public Health Association, about one in four school-aged children has a vision problem that interferes with learning.  Here is a brief overview of some eye conditions that are relevant to this age group:

• Hyperopia, myopia, and astigmatism:  These are all types of refractive error.  A refractive error exists when the eye doesn't focus light exactly on the back of the eye (the retina).  An eye doctor measures the refractive error of the eyes and prescribes glasses/contact lenses if needed.  Correcting a child's refractive error when appropriate is the first step in addressing problems with the visual system because it may be the root cause of other vision problems, like those described later in this post.  
• Hyperopia, or farsightedness, is when the eye focuses light behind the retina.  Small amounts of hyperopia are normal in young children.  Kids can often compensate for this by using their eye muscles to bring images into focus.  But when the amount of hyperopia is substantial, it creates an unnecessary burden on the system and can result in blur, fatigue, eye strain, and headaches, especially when reading.  High amounts of uncorrected hyperopia can cause an inward eye turn to develop as well (accomodative esotropia).  
• Myopia, or nearsightedness, is when the eye focuses light in front of the retina.  Those with myopia have difficulty seeing far away.  Myopia is often first detected in school-aged children, and typically progresses through the adolescent years.
• Astigmatism is when the curvature of the cornea and/or the lens of the eye is different in one direction than it is in another, and light gets focused at two different points.  This can cause blur and distortion up close and far away.    
• Strabismus:  Commonly called crossed eyes, strabismus is a misalignment of one or both eyes, present in 2-5% of the general population.  The eye may turn in (esotropia), out (exotropia), up (hypertropia), or down (hypotropia).  It may happen all the time, or it may happen only some of the time (constant vs. intermittent).  The turned eye may be the same eye all the time, or it may alternate between the two (unilateral vs. alternating).  When the eyes are pointing in two different directions, they are sending the brain two different images.  Depending on the frequency and severity of the eye turn, it may cause double vision.  Alternatively, the brain may learn to ignore the image from the turned eye in an attempt to relieve the confusion.  This adaptation is called suppression.  If left uncorrected, strabismus can result in decreased vision in the turned eye (ambylopia) and loss of depth perception.     
• Amblyopia:  Sometimes referred to as lazy eye, amblyopia affects 2-3% of the general population.  Amblyopia is defined as reduced vision in one eye, or less commonly both eyes, in the absence of disease or structural abnormalities.  It can be caused by an eye turn (strabismic amblyopia), or a high prescription in one or both eyes that hasn't been corrected (refractive amblyopia), or something physically obstructing the line of sight (deprivation amblyopia).  Amblyopia occurs in the brain during the developmental stage, and it is often a preventable and treatable cause of vision loss.  The sooner it is diagnosed and treated, the better the chance of achieving normal visual function.  This is a big reason why eye exams are recommended early in life. 
• Ocular motor dysfunction (OMD):  Patients with OMD have problems keeping their eyes on a target (fixation), moving their eyes quickly and accurately from one target to another (saccades), and following a moving target with their eyes (pursuits).  These eye movements play an important role in reading and sports.  OMD usually does not present by itself; a child with OMD may also have issues with focusing and/or eye teaming.  The primary treatment here (assuming the appropriate glasses prescription has been given) is vision therapy.    

Vision therapy is a program of activities designed to help correct deficiencies and improve efficiency of the visual system.  Vision is a developed skill, and thus can be enhanced with guided training.  Vision therapy can be prescribed to help treat some conditions I mentioned above, as well as others relating to focusing and/or eye coordination.  Not all optometrists offer vision therapy, but all optometrists can direct you to one in your area that does provide such services.

CliffsNotes: Be sure to add a comprehensive eye exam to your child's yearly back-to-school checklist.  Clear, comfortable, single vision is important to a child's academic success!

     Additional recommended resources:

• Vision and Learning
• College of Optometrists in Vision Development

(1) Gazzaniga MS, Ivry RB, Jangun CR. Cognitive Neuroscience, the Biology of the Mind. New York, NY; WW Norton & Co, 1998.