Vision is our most important sensory modality: 80% of what we learn is achieved through our visual system. However, we easily underestimate this important information system (the visual system).
In many instances, children who manifest visual problems or whose visual abilities are not well integrated will have difficulties to perform properly at school.
Unfortunately, many still believe that a child who has “good vision” (a visual acuity of 20/20 or 100% at far) should be performing well in school and that learning or reading difficulties are then not related to their vision…
To really understand what we, optometrists specialized in visual training, mean by the word “vision”, we will discuss the four components of vision:
1- THE STRUCTURAL COMPONENT (OCULAR HEALTH)
This first component consists of eye health.
Fortunately, the frequency of eye diseases in school age children is very low. Approximately, 1% of children have eye diseases at birth. Needless to say, eye diseases are not related to learning or reading difficulties.
2- THE OPTICAL COMPONENT
This component determines if the child can see clearly at far: he may be nearsighted (myopia), farsighted (hyperopia) or have astigmatism. But “seeing clear” at far is not the whole aspect of vision. By experience, we know that 95% of children who have learning or reading disabilities, for example, can see clearly at far. Near vision is thus more important than far vision and has to be assessed.
Among the problems we find in this component are: child reads or writes very close, vision can be blurred in books, child cannot sustain proper concentration or attention, he does not understand easily what he reads.
Reading glasses (for the brain) can help children decode or perform better and sustain focus longer while reading.
3- THE FUNCTIONAL COMPONENT
Another aspect of vision is how the eyes function together. Here, we must assess how well the focusing mechanism of the eyes can perform (if not performing well, near vision will be blurred), how the eyes are aligned (visual-motor coordination), and if eye tracking (eye movements) is easy, smooth, precise. Needless to say adequate eye movements are essential to good reading! Unfortunately, this functional component is not always tested in a conventional eye examination.
Among the problems we find here are: the child cannot focus on what he reads or writes more than a few minutes (homework takes forever), the child tires easily when reading because of the muscular effort required, and eye movements are jerky, imprecise and head movements are most often used (instead of eyes).
“Saccades are the ability to switch fixation from one target to another. This skills permits easy shifting of the eyes along the line of print in a book, a rapid and accurate return to the next line, and quick and accurate shifts between desk and chalkboard, or from one distance to another. By the time child starts reading his eyes are capable to read at least 11 character letters at a time before his eyes start shifting. Inadequate eye movement control may cause a child to lose his place while reading, have difficulty copying from the blackboard, and skip or omit words when reading.”
(Jean Ayres, Sensory Integration and the child)
4- THE PERCEPTUAL COMPONENT
The perceptual abilities of the child are the refinement and the end-product of all visual abilities: perceptual-motor abilities are related more directly to the ability to decode visual information.
Among the perceptual abilities we must assess are: form perception (can child recognize basic forms?), eye-hand reproduction (can child reproduce with hands what eyes see?), eye-hand coordination (are eyes and hand matched to perform adequately?), visual memory, auditive memory, etc.
Among the perceptual problems we can find are: form perception is weak, eye-hand coordination is difficult, visual and/or auditive memory is low, fine motor control of the hand is inefficient.
All these visual and perceptual abilities are of great importance: they help make the child succeed in school. We must remember that for children, the most difficult task in life is to learn to read and write. A complete visual-perceptual examination is thus required to be able to analyse how the child performs visually and perceptually.
“Visual perceptual skills relate to the ability to understand and interpret symbols, shapes, numbers, and letters. For such skills as reading readiness, puzzle completion, and figure ground perception. In other words, it is the capacity to interpret or give meaning to what is seen. This includes recognition, insight, and interpretation. Visual perception is made
up of several categories.”
(Jean Ayres, Sensory Integration and the child)