Normally a combination of deficits, rather than just one, are at the root of a child’s reading difficulty. Reading requires the integration of a number of different vision skills: visual acuity, visual fixation, accommodation, binocular fusion, convergence, field of vision, and form perception. Often vision related reading deficits are overlooked due to children not complaining about how they see. Often they have passed school vision screenings which give them an “OK” on their acuity.
Visual acuity is the ability to see objects clearly. It is usually the only skill assessed in a school vision screening. The typical school eye chart is designed to be seen at 20 feet and measures how well or poorly the child sees at that distance.
Reading requires the integration of a number of different vision skills: visual acuity, visual fixation, accommodation, binocular fusion, convergence, field of vision, and form perception.
Fixation is the skill utilized to aim the eyes accurately. Static fixation is the ability to focus on a stationary object when reading a word or working a math problem. Saccadic fixation is the ability to move the eyes quickly and accurately across a page to read a line of print. Pursuit fixation is the ability to follow a moving object with the eyes.
These complex operations require split second timing for the brain to process the information received and to track the path of the moving object.
Accommodation is the ability to adjust the focus of the eyes as the distance between the individual and the object changes. Children frequently use this vision skill in the classroom as they shift their attention (and focus) between their book and the chalkboard for sustained periods of time. Being able to maintain focus at near for sustained periods of time is important for reading, writing and also taking tests.
Binocular fusion refers to the brain’s ability to gather information received from each eye separately and form a single, unified image. A child’s eyes must be precisely aligned or blurred or double vision, discomfort, confusion or avoidance may result.
If that occurs, the brain often subconsciously suppresses or inhibits the vision in one eye to avoid confusion. That eye may then develop poorer visual acuity (amblyopia or lazy eye).
Convergence is the ability to turn the two eyes toward each other to look at a close object. School desk work and reading are two instances in which a child depends on this vision skill.
Field of Vision
Field of vision is the wide area over which vision is possible. It is important that a child be aware of objects in the periphery (left and right sides and up and down) as well as in the center of the field of vision. Near central or Para-central vision is important for reading ability.
Visual perception is the total process responsible for the reception and understanding of what is seen. Good visual perception is necessary for successful school achievement.
Form perception is the ability to organize and recognize visual images as specific shapes. The shapes the child encounters are remembered, defined and recalled when development of reading skills begin.
Signs of reading-related vision problems
- holds book or paper too close
- frequent eye rubbing during reading or homework
- loses place or rereads lines when reading, which often gets worse with time
- omits or substitutes words
- uses finger to read
- homework is slow
- reading comprehension decreases with time
- avoids reading
- slow reading speed
- tilts or turns head
- closes or covers one eye
- squints or blinks during reading
- red or watery eyes after reading
- crossed or drifting eye
- clumsy, poor depth perception
Symptoms of reading-related vision problems
- headaches, worse later in the day
- eyestrain, sore eyes
- tired, burning or itchy eyes during reading
- double vision
- words move or run together when reading
- blurry vision when reading or copying
Treating reading-related vision problems
An optometrist will examine these vision skills and determine how well the child is using them together. When a vision problem is diagnosed, he or she can prescribe glasses, vision therapy or both.
Vision therapy has proved quite effective in treating reading-related vision problems through individualized programs designed to help a child acquire or sharpen vision skills that are necessary for reading.
Treating reading problems
Because reading problems usually have multiple causes, treatment must often be multidisciplinary. Educators, psychologists, optometrists and other professionals must confer and work together to meet each child’s needs.
The optometrist’s role is to help the child overcome the vision problems interfering with the ability to read. Once this is accomplished, the child is then more capable of responding to special education efforts aimed at treating the reading problem itself.