About normal visual development
We are born with a wonderful visual equipment set that includes: the sensory system – the two eyes, that focus and detect light and patterns and translate the light impulses into nervous activity; the motor system – 12 ocular muscles (6 for each eye) that move the eyes in a coordinated way; and the brain, the organ which registers and interprets vision and controls and coordinates the motor and sensory systems. These act as a harmonious whole to enable meaningful vision.
Whereas the eye of newborn baby is mostly fully developed at birth, the brain is still in a very plastic stage and still needs to ‘learn’ to see and interpret the visual world. Neural connections evolve in response to visual input from both eyes, in much the same way as with speech and language. The ‘plastic’ period for speech and language acquisition is up until 8-12 years of age. After this, it becomes progressively more difficult for instance to learn a new language as a mother tongue. Visual development is similar. The brain requires equal focused input from two eyes and good alignment of the two eyes stabilised by the ocular muscles during the developmental or plastic stage. If the two eyes are not properly aligned, or if there is a large difference in refractive error between the two eyes, it is possible for the brain to make use of the input from one eye tat the expense of its fellow and for the fellow eye to lose its competitive advantage. This is what we refer to colloquially as a ‘lazy’ eye. But it could be that the ‘lazy’ eye is in fact normal, but the brain has merely not learnt to use the information from this eye. Treatment is aimed at redressing this imbalance.
For this reason it is important to attend to childhood eye conditions in a timely fashion. If the eyes are not properly aligned at birth, commonly known as a squint, this needs to be assessed and treated appropriately and early. It is also important that children be screened at 3.1/2-4 years of age, before starting school, when the child is generally cooperative enough to assess acuity of vision and refractive error, but while there is still sufficient brain plasticity to correct the situation with glasses and occasionally patching of one eye to allow the brain to learn to see equally well with each eye.
If there is any concern about an infant’s or child’s eyes or vision, it is important to seek ophthalmic consultation.