Short-sighted prescribing

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The practice of "under-correcting" children's eye problems could actually make them more short-sighted, according to new research.

For decades, opticians have prescribed slightly weaker glasses for children, in the hope that their eyes will strengthen.

Now, it seems that the opposite may be true.

On Breakfast at 7.10am, we talked to the man behind the research, Professor Daniel O'Leary

His study, reported in The New Scientist magazine this morning, suggests that millions are becoming more short-sighted than they need - and some may suffer serious complication such as a detached retina.

He explained in detail why people are short-sighted - and why glasses should be full strength.

People become short-sighted when their eye ball becomes slightly lengthened - meaning that light-rays are not perfectly in focus when they reach the retina at the back of the eye.

"Current theory is to leave the images focused slightly in front of the retina - but it was proved wrong," he told Breakfast.

"In short-sighted children, the eyes actually elongate faster (making short sight worse).

"My advice to parents is to wait until their child's next eye test and then ensure that their prescription is full strength"

He also added that there's no cure for short-sight: once the eyeball has elongated, it can't get shorter again.

click here to watch Professor O'Leary's interview in full

Further details from BBC News Online

Optometrist Daniel O'Leary, of Anglia Polytechnic University in Cambridge, studied 94 children in Malaysia.

The study was meant to run for three years, but was cut short after two years when it became clear that the children's eyesight was getting worse.

Strong evidence

Paul Adler, of the College of Optometrists, said: "It is the strongest evidence I have seen in this field.

"It could change prescribing practice worldwide."

Short-sightedness is caused by the inability of the muscles in the eye to flatten the lens enough to focus light from distant objects directly on to the retina.

Instead, the point of focus is in front of the retina, leading to a blurred image.

Glasses correct the problem by moving the focal point back onto the retina.

But when people wearing normal glasses look at close objects, the focus point is usually behind the retina.

The theory is that to try to "refind" this focal point for near objects, their eyeballs actually elongate.

Not only does this make distance vision even worse, it also increases the risk of serious eye diseases such as retinal detachment, glaucoma and retinopathy, all of which can lead to blindness.

According to this theory, undercorrection should help stop the eyeball elongating.

When they undercorrect, optometrists prescribe a lens that focuses light from distant objects just in front of the retina, rather than exactly on it.

Theory

No glasses is the worst option of all

Daniel O'Leary

However, the theory is based on the scantiest of evidence - a study of just 33 Japanese children in 1965, and animal studies involving chicks.

Mr O'Leary's team undercorrected the sight of half the children, and fully corrected the rest.

Then they measured the length of the eyeball with ultrasound every six months.

They found that the eyeball elongates faster when vision is undercorrected.

As a result, the vision of the children with undercorrected short-sightedness deteriorated more rapidly.

Mr O'Leary believes the eye cannot tell whether the focal point is in front of the retina or behind it. Instead, it just grows backwards if the image is out of focus.

"No glasses is the worst option of all," he said.

"But don't undercorrect. Go for full correction."

Frank Munro, president of the College of Optometrists, told BBC News Online that the practice of undercorrection was no longer used.

However, he said it had been employed by optometrists in the past.

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