Its a myth. In 2007, two doctors (Rachel Vreeman and Aaron Carroll ) published a study debunking a series of well known medical myths, including the idea that reading in dim lightcauses eye damage.  The only negative effects are eye strain, which may cause headaches, and dry eyes since people blink less in dim light. Both of these are short-term.

I suspect your mother may be more concerned about you not getting enough sleep if you are reading too late.

It is nice to know of a youngster who is as fond of reading as some of our friends used to be, but although I have always been inclined to pooh pooh that Urban legend, I am bothered. Neither my wife or I needed glasses till well advanced in years, whereas both out children needed glasses by the time they were halfway through primary school. Like us, only more so, they were early readers and they both read in bed and a lot of time besiides. One of them read with one eye buried in his pillow, and he wound up with "lazy eye".

Not so long ago I read this in NS:

Remember when your mum told you that playing outside was good for you?

She may have had a point, at least as far as your eyesight is concerned. Researchers in Australia have found an association between high levels of outdoor activity and low rates of short-sightedness, or myopia, in children.

The prevalence of childhood myopia has increased dramatically in recent decades. With rates of 80% in some East Asian populations, the search is on for possible causes.

"We know that there are genetic associations with myopia," says Kathryn Rose of the University of Sydney in Australia. "But the rapid changes in myopia prevalence are not consistent with a simple genetic determination, since gene pools do not change sufficiently fast."

Suspecting that environmental factors might also be involved, Rose and colleagues set about investigating the effect that time spent outdoors has on the prevalence of myopia. In the study, 2367 12-year-old Australian schoolchildren underwent eye examinations and completed questionnaires about their daily activities.

The lowest rates of myopia were associated with the highest rates of outdoor activity, irrespective of how much near work, such as reading, the children did.

The children with the worst eyesight did lots of near work and spent very little time outside. Interestingly, the study found no benefit from playing sports indoors. "The crucial factor was being outdoors," says Rose.

"Time spent outdoors, as a protective factor, now appears to be the strongest environmental factor that has yet been documented."

The researchers think the reason for this might be the light intensity children are exposed to outside. Rose explains that children's eyes grow as they get older but, for reasons not yet understood, the eyes of children who develop myopia grow excessively, leading to a mismatch between the optical power of the eye and its axial length.

"The release of dopamine from the retina is promoted by higher light intensities, and there is also evidence that dopamine can act as an inhibitor of eye growth," says Rose. "This provides a very plausible mechanism by which time spent outdoors could prevent the development of myopia."

But Karla Zadnik of the Ohio State University College of Optometry points out that other explanations are possible. "Perhaps myopic children are simply more comfortable indoors, engaged in more sedentary activity," she says.

Journal reference: Ophthalmology (DOI: 10.1016/j.ophtha.2007.12.019)

So...

I dunno, but if we had our chance over again, we would have given this matter some thought.

You think too!

Cheers,

Jon