( BBC ) - Children with a lazy eye do not need to wear an eye patch for the whole day to correct their vision, say experts.
A study carried out in two London hospitals found three to four hours a day for 12 weeks is enough to improve sight in affected children.
Wearing a patch can cause considerable distress and should be done as little as possible, the researchers said in the British Medical Journal.
Around one in 50 children in the UK suffers from the condition.
Screening is done in children of school age to identify children with lazy eye disease or amblyopia - a disorder where vision in one eye does not develop fully during early childhood.
It is commonly treated by making the lazy eye work harder to see by blocking the vision of the good eye with a patch
Glasses are also used to help correct the vision.
However, there is huge variation in practice and some experts advocate using the patch for the whole day.
Many others prescribe a patch for more than six hours a day.
Monitoring
To find out the best strategy, researchers from City University in London studied 80 children who were told to wear their patch for either six or 12 hours a day.
They also developed a device for monitoring how often the child did in fact wear the patch.
Before starting with the patch the children wore glasses for 18 weeks and vision was checked every two weeks.
Neither group wore the patch for as long as they were supposed to.
But wearing the patch for three to six hours a day was just as effective as wearing it for six to 12 hours a day, the researchers said.
The younger children were, the less patch time they needed to correct their vision.
Study leader, Professor Alistair Fielder, an expert in ophthalmology, said children did not like wearing an eye patch and were more likely to stick with it for just a few hours a day.
"Firstly you're asking a child to wear a patch on their face which separates them from their peers and secondly to use an eye which doesn't work very well so it's a pain for them."
He also recommended that glasses should be prescribed first to improve vision rather than at the same time as the patch as currently happens.
"What I'm really pleased about is we're getting an insight into how the treatment works and how quickly it works which means when you're entering discussions with parents they're better informed."
Anita Lightstone, head of services development at the RNIB said the issue had been debated for some time.
"To have a really good study to show you don't need to wear the patch all the time is brilliant and it will be a lot easier for children."
She said the earlier affected children were identified the better and urged parents to make use of free eye checks on the NHS if they had concerns.