Prescribing spectacles for very young children may alter the way that their eyeballs grow and affect their vision later in life, US research has indicated.
Earl Smith and his colleagues from the University of Houston, Texas, found that putting lenses over the eye of a young monkey to change the eye's focus would also change the way the eye grows. The eyeball grew to compensate for the effect of the lens so that when the lens was removed the eye had grown "naturally" out of focus.
Their experiments demonstrate that in early life visual feedback - whether images are in focus or not - controls the growth of the eye.
Their results suggest that it may one day become possible to correct myopia (short-sightedness) or far-sightedness by altering the way the eye grows so it returns itself to normal vision.
The researchers' measurements corresponded to approximately the first two to three years of a human infant's life. But Dr Smith warned it would be wrong to interpret his results as suggesting that spectacles do young children harm. "In certain very young infants, spectacle lenses are critical for the prevention and treatment of conditions, like amblyopia or lazy eye, that can otherwise lead to permanent and severe defective vision." These children need and benefit from spectacles, he said.
At birth, infants are usually moderately far-sighted, Dr Smith said. Over the first few years of life their eyes develop into near-perfect optical states.
His research shows that if a lens artificially made the eye far-sighted then the eyeball would grow longer than normal and so become less far- sighted, reducing the amount of defocus produced by the lens.
"We simply do not know if the results that we obtained from our very young monkeys can be used to explain why schoolchildren often develop near-sightedness," Dr Smith said. But "it may be possible to promote normal eye growth via spectacle lens correction".Reuse content