How a child learns to see…
“Vision” encompasses far more than visual acuity. Vision is a dynamic process that is constantly in flux – not only the complex nature of rods for peripheral vision and cones for central acuity is taken into account, but also that there are two eyes that must learn to team together. Vision must address accommodation and convergence/divergence and the relationship between them, fixation ability, saccadic eye movements, and pursuit eye movements. Also considered are vision perception skills – form and shape recognition, figure-ground appreciation (the crowding phenomenon), visual attention span, vision-auditory matching, rhythm, centration, bilaterality, directionality, and eye-hand coordination as well as all eye – body motor integrations.
“Vision” is a learned process. An infant is born with a potential to see, and genetics that help guide or influence that development – sometimes for the good and sometimes for the bad. Learning to see involves experiencing visual stimuli to enforce the ability of neuro-connections to become active and work properly. Not only for “acuity,” but also for development of vision skills – fixation ability, eye alignment, tracking and saccadic eye movements, as well as various vision perceptual skills. Vision skills are integrated into the other motor systems of the body.
Six major developmental processes or patterns are involved:
1) The child is born with the potential to see. For visual acuity to develop, each eye must be stimulated with light and moving objects. Interaction with the baby’s environment is critical for this process to occur. Any physical or neurological event that prevents stimulation of one or both eyes can seriously jeopardize visual acuity development.
To see a simulation of how a baby develops visual acuity in the first year of life, click on the link below. This is in a pdf format.
2) The second process is the hierarchy of motor skills: Large motor skills, fine motor skills, eye motor skills, visualization. Each level is built on the base of the previous levels. This is best explained with this simple analogy. A baby hears a knock on the door. As an infant, the baby turns his body to “see.” As motor skills develop, as the baby hears the knock he turns his head to “see.” As motor skills refine, a baby hears a knock and turns his eyes to “see.” And as a baby becomes a toddler with experience, a child can visualize a person at the door without having to look because that is what happens when he hears a knock on the door.
3) The third pattern is “space awareness.” Three basic questions are answered: Who am I? -what is this body I was born with and what can I do with it? A baby learns to move arms, legs, hands, all motor functions of the body. Where am I? - where do I fit into the world? Where is the world in relation to me? – how can I judge my surroundings, my location, other items in relation to my position. Vision is the sense that allows the best ability to achieve this space awareness. Deficiencies in this development can lead to disruptive behavior, even emotional fears of new settings or surroundings.
4) The fourth developmental pattern is that of “midline.” This critically applies to eyes because we have two eyes, two eyes that must make a decision to work together, fight each other, or learn to eliminate one or the other (suppression). The body has two sides; do they work together or fight each other? It is a learned pattern of motor movements. If that development is delayed, disrupted, or is not experienced, a sense of midline may not be established. It is this midline that gives each person a sense of left and right. If there is no midline, often the two eyes will not learn to work together either. This may be expressed by amblyopia, or perhaps via eye alignment with exo or eso postures, either as phorias or strabismus. Also, a person fails to get a sense of laterality (understanding “sides”), and that will translate into failure to understand and project directionality (left-right awareness). This is a source of reversals and sequencing errors. Left and rights have no meaning to these kids because they have no point of reference to draw from. A “b” and a “d” are essentially the same letter because they are loops on sticks. The fact that the loops are on different sides really does not matter because sides do not matter.
5) Understanding the visual world. Vertical lines come first, then horizontal, then oblique. This acceptance occurs both in the visual world and in the eye-hand coordination process. On copying tasks vertically oriented lines are easiest to copy, then horizontal, then oblique. On copy forms it is common to see children turn their paper, their heads, or even their bodies to orient horizontal or oblique lines into up and down positions
6) The final developmental pattern is the hierarchy of senses. Babies find taste and touch very important as they explore their new world. Hands must be on everything, and when they get a hold it goes straight to the mouth. If a child is to succeed, vision must take over as the dominant sense of the body, guiding that individual though life. Children that struggle with this pattern are the kids who continue to have to touch everything. Even if they use “vision,” they still need that tactile feedback of touching to allow them to concentrate visually on whatever it is they are analyzing. Eyes must learn to lead the body – we call it EYE-HAND coordination, not HAND-EYE coordination.
Recognizing the importance of these skills, it is prudent to recognize early that early intervention of any of these patterns of processes that have gone awry can be much more effective treatment than trying to address problems after three, five, ten, even twenty years of poor performance and frustration in school, athletic, or vocational struggling. Vision development is far too complex to be left to chance, and why the early infant eye health and vision assessment is so important.