By Sam Sokol, Ph.D.
In 1890, the psychologist William James said, 'The baby, bombarded by sensations from the eyes, ears, nose and skin all at once, feels that all the world is one great blooming, buzzing confusion."
At the time, Professor James' eloquent statement about babies was quite reasonable. Actually, we know now that his statement is not true – the world is not all one big, buzzing confusion to babies, at least not when one talks about babies' vision.
While the visual capacities of the human baby are not fully developed at birth, babies do see and recognize large objects – such as a human face – and can distinguish colors such as red and green. During the first six months of life the infant's visual system develops rapidly; after six months, vision develops more slowly and reaches full maturity by four to five years of age.
One of the most important aspects of visual development is the ability to distinguish fine detail. In adults, the most common test of vision is the Snellen chart – the chart at the end of the eye exam room with which everyone is familiar. Since infants cannot read the Snellen chart, other techniques that do not require the baby to talk to us are used. At New England Eye Center we most commonly use the Visually Evoked Potentials test (VEP) and the Preferential Looking test (PL).
The VEP test measures the brain waves coming from the vision center of the brain. A small electrode is taped to the back of the baby's head (this is where the ''Vision Center" is located). The baby sits on the parent's lap in front of a television and watches black and white squares move back and forth on the screen. The electrode records electronically the signals that are sent from the eye to the brain. The smaller the size of the squares that can produce an electrical signal from the brain, the better the vision. The strength of the brain wave signals is converted to standard vision notation (the "20/20" type of designation).
The Preferential Looking test (PL) is based on the fact that an infant, given a choice, looks at a pattern of stripes rather than at no stripes at all. The baby is shown a card with stripes on one side of it, either to the baby's left or to his right. An observer behind a partition watches the baby's eyes to see if they look at the target with the stripes. If so, smaller stripes are used until the child no longer looks at the striped card. The size of the stripes that the child can see determines the baby's vision.
At what age does a child see as well as an adult? At birth, an infant sees between 20/400 and 20/800 (which means that the child can see an object seven inches wide at twenty feet). By one month the vision improves to 20/300, and by six months to 20/50-that's almost Driver's License vision!
Perhaps if William James were alive today, he'd tell us: 'The baby, bombarded by sensations from the eyes and the other senses, sees that all the world is one big, blooming, beautiful place!"
The Pediatric Ophthalmology and Strabismus Service is located in the same office as the Electrophysiology Service, which measures vision in preverbal children using visual evoked potentials and preferential looking techniques.
Pediatric patients with cataracts, glaucoma, corneal and retinal disorders are provided a full range of diagnostic and therapeutic services in conjunction with other New England
Schedule an appointment or contact us at 617-636-6769.