Children with amblyopia (commonly known as lazy eye) need only wear an eye patch for three to four hours a day for 12 weeks to improve vision, and those aged under four around three hours, rather than the six to 12 hours usually recommended by doctors, according to a new study as quoted by media reports Friday. 

The study involved 97 children aged 3-8 years with a confirmed diagnosis of amblyopia. All children had a full ophthalmic assessment and were instructed to wear glasses all the time for 18 weeks.

Three children are wearing eye patches. Children with amblyopia need only wear an eye patch for three to four hours a day for 12 weeks to improve vision, and those aged under four around three hours, rather than the six to 12 hours usually recommended by doctors. (photo: file photo from Xinhua)

On completion of this phase, researchers at City University in London and McGill University in Montreal asked 80 children who still met the study's definition of amblyopia to wear a patch for either six or 12 hours a day.

The patch was fitted with sensors that were wired to a data logger, which recorded how long the patch was actually worn. Visual function was recorded every two weeks.

The point of the study was to see which eye patch "dose" was more effective.

It is found that, on average, the six-hour group wore the patch for 4.2 hours a day, while the 12-hour group wore it for 6.2 hours.

However, the visual improvement between the two groups was the same.

Wearing the patch for less than three hours led to a much slower improvement across the two groups.

Children under four years of age required significantly less occlusion (under three hours a day) than older children to correct their vision. Patching beyond 12 weeks did not confer additional benefit.

This analysis suggests that achieving an initial dose rate of three to four hours a day should be a clinical priority.

Eye patching can cause considerable distress for both the child and family, researchers said, so doctors should try to minimize the "dosage" for the best expected outcome.

Blurred vision or crossed eyes are the typical symptoms of amblyopia, caused by a disturbance in the pathway of vision between the eyes and the brain.

(Agencies via Xinhuanet.com September 14, 2007)