Night-lights reprieved in new myopia study

Leaving a night-light on in a child's bedroom will not cause them to become short-sighted in later life, according to a study that contradicts earlier findings published last year.

Leaving a night-light on in a child's bedroom will not cause them to become short-sighted in later life, according to a study that contradicts earlier findings published last year.

An investigation of more than 1,200 children found no link between short-sightedness and whether they had slept with a night-light on before they were two years old.

A smaller survey of 479 children found last year that babies under two who slept in a partially lit room were up to five times more likely to develop myopia compared with children who slept in the dark.

However, the latest findings cast doubt on the conclusions drawn from the earlier research and will reassure parents who allow their children to sleep in a dimly lit room.

Karla Zadnick, a member of the research team at Ohio State University in Columbus, found there was a link between short-sighted parents, who probably used night-lights to compensate for the own eyesight, and short-sighted children

The study, published in the journal Nature, found that 20 per cent of the 417 children who had slept in the dark developed short sight. This compared with 17 per cent of those who had slept with a night-light and 22 per cent of those who had slept in a fully lit bedroom.

"Across nursery lighting conditions, the percent of children in our study who eventually developed myopia was very similar. Parents should be reassured by these results and not concern themselves with this unfounded risk," Dr Zadnick said.

Richard Stone, professor of ophthalmology at the University of Pennsylvania Medical Centre in Philadelphia, suggested in the earlier study that night-lights could stimulate eye growth, with bigger eyes being more prone to myopia.

However, Dr Zadnick and her colleagues believe Professor Stone should have investigated the short-sightedness of the parents in his study as myopia is known to run in families. She found that short-sighted parents are more likely to use a night-light in their child's bedroom. "We think this may be due to the parent's own poor eyesight," she said.

Another possible explanation is that parents in higher socio-economic groups are more likely to be short-sighted and are also more likely to buy night-lights for their children.

Dr Zadnick also pointed out that the children in Professor Stone's study were attending an eye hospital, and so were not a representative sample.