Tuesday September 18 2007
Eye patches are used to correct amblyopia
Children with a lazy eye (amblyopia) do not need to wear an eye patch all day to improve their vision, reported the BBC. The news report said there was huge variation in the treatment of lazy eye, which involves wearing a patch over the good eye to force the lazy eye to compensate, and therefore improve. The report was based on a study that found that wearing a patch for 3 to 6 hours was as effective as wearing it for 6 to 12 hours.
This study was a good quality randomised controlled trial. It shows that children told to wear an eye patch for 6 hours will achieve similar benefits to children who are told to wear one all day. However, children who are told to wear a patch all day actually wear it for only about half this time.
This study shows that getting children to wear an eye patch all day is probably not feasible in most cases, and that prescribing 6 hours a day instead is not detrimental to vision, and is more likely to be acceptable to the child.
Where did the story come from?
Doctor Merrick Moseley and colleagues from City University, London, and McGill University, Montreal carried out this research. The study was funded by Fight for Sight, UK. The study was published in the peer-reviewed British Medical Journal.
What kind of scientific study was this?
This was an unblinded randomised controlled trial, and part of the randomised occlusion treatment of amblyopia study (ROTAS).
Researchers recruited children aged 3 to 8 years old who had amblyopia (lazy eye), and significantly poorer sight in one eye than the other. The children received a thorough eye examination, and glasses were given to the children who needed them. The children given glasses and those who already had glasses before the eye examination, but had worn them for less than 18 weeks, were then asked to wear them for an 18-week period.
The 90 children who still had a lazy eye after 18 weeks of wearing glasses, and those who did not need glasses, were then randomly assigned to one of two groups. One group was asked to wear an eye patch on the non-lazy eye for 6 hours a day and the other for 12 hours a day. To measure how long the patches were actually worn, electronic monitoring devices were placed within each patch.
Researchers tested the children’s eyes every 2 weeks, and the children continued to wear the patch until their eyesight stopped improving. Researchers then compared improvements in eyesight between the two groups.
What were the results of the study?
It was found that children needed to wear the patch for nine weeks on average, to achieve the best results. Both groups showed similar improvements in vision in the lazy eye.
On average, the children in the 6 hours group only wore for the patch for about 4 hours, and the children in the 12 hours group wore it for 6 hours. Further analysis of the results showed that children who wore the patch for less than three hours a day had less improvement in their vision than those who wore it for longer.
What interpretations did the researchers draw from these results?
Researchers concluded that prescribing an eye patch for 6 hours a day has a similar effect on vision to prescribing 12 hours a day in children with a lazy eye, and that wearing a patch for 12 hours is “almost certainly excessive”. They also found that children wear their patches for much less time than they had been prescribed.
What does the NHS Knowledge Service make of this study?
This was a well-designed study, and so should provide reliable results.
The objective measurement of the length of time that children will wear an eye patch, shows that they do not wear it for significantly longer if they are told to wear it all day than if they are told to wear it for only 6 hours a day. It is important to note that in both groups children did not achieve their prescribed duration of wearing an eye patch. This suggests that for children to benefit from wearing an eye patch, which apparently requires a minimum of 3 hours a day, children will still need to be prescribed at least 6 hours of daily wear.
The results of the analysis by actual duration of eye patch wearing as measured by the monitoring device, which suggests that a minimum of three hours daily wear is required to achieve benefit, should be interpreted with some caution. The actual duration of wear was not randomly allocated, but was determined by the children themselves. This means that unknown factors could have influenced the results.
Too few children in this study complied with the prescribed 12 hour dose of eye patch wear (only 7 out of 40 children were 90% compliant) to draw any firm conclusions about its potential benefit, or lack of benefit, compared with shorter wear. Therefore the authors’ conclusions that “patching for all waking hours is almost certainly excessive” is probably premature. However, what this study has shown is that getting children to wear the eye patch for this long is not feasible, and that prescribing 6 hours a day instead is not detrimental to vision, and is more likely to be acceptable to the child.
Sir Muir Gray adds...
Every patient is unique and so treatment should be tailored to each patient’s needs. Patients need bespoke treatment plans, not off–the-peg solutions. Bespoke treatment often uses less resource and is always more acceptable, and unlike the rag trade, it does not have to cost more than off-the-peg. In fact, as this study shows, it can cost less.