What is amblyopia?
Amblyopia (or ‘lazy eye’) is blurred vision caused by one or both eyes not being stimulated properly in childhood. It is so common that it is the reason for more vision loss in children than all other causes put together.
Amblyopia can happen even when there is no problem with the structure of the eye. The decrease in vision occurs when one or both eyes send a blurry image to the brain. The brain then “learns” to only see blurry with that eye, even when glasses are used.
Only children can get amblyopia. If it is not treated, it can cause permanent loss of vision.
What are the causes of amblyopia?
There are several different types and causes of amblyopia:
- Stimulus deprivation amblyopia is caused by a reduction of light entering the eye, for example, in cases of cataract. If not treated very early, these children can have very poor vision.
- Refractive amblyopia is caused by a need for glasses. Glasses can be required in either one or both eyes, but there is often an unequal glasses prescription between the eyes. In these cases, the eye needing the stronger prescription (usually hyperopia and/or astigmatism) becomes amblyopic. These children sometimes, but not always, have squints.
How do I know if my child has amblyopia?
The end result of all forms of amblyopia is reduced vision in the affected eye(s). However, measuring vision in young children can be difficult.
Parents may not think there is a problem because their child’s eyes may look straight. Also, the “good” eye may have normal vision, so the child may appear to see as well as other children. For these reasons, amblyopia in some children may not be found until the child has a vision screening test.
Will glasses help a child with amblyopia to see better?
Maybe, but they may not correct it all the way to 100%. With amblyopia, the brain is “used to” seeing a blurry image and it cannot interpret the clear image that the glasses produce. With time, however, the brain may “relearn” how to see and the vision may increase.
The first step is prescribing the glasses and getting the child to wear them full-time. The earlier the child starts to wear the glasses, the quicker they will get used to them.
Following a period of time in full-time glasses, the child is reviewed in the eye clinic, usually about 3 months later. If there is amblyopia at this visit, the child may need to start patching.
When should amblyopia be treated?
Early treatment is always best.
How old is TOO old for amblyopia treatment?
If there is a squint, treatment will probably need to be completed by the age of 7. Other types of amblyopia may respond to treatment beyond this age. However, the earlier treatment commences, the better chance of success.
How is amblyopia treated?
One of the most important treatments of amblyopia is correcting the initial cause of the amblyopia, ie, the refractive error, the cataract, etc. This may improve vision.
Following this, treatment is started to encourage use of the non-dominant eye. This is usually done by patching the good eye, or using Atropine eyedrops to blur the good eye.
Treatment should be carried out under supervision, and with regular appointments to monitor progress.
Many parents find that coloured patches can improve compliance.
How long does amblyopia patching therapy take to work?
Although an improvement in vision frequently occurs within weeks of beginning patching treatment, optimal results often take many months. Once vision has been improved, part-time (maintenance) patching or periodic use of Atropine eyedrops may be required to keep the vision from slipping or deteriorating. This maintenance treatment may be advisable for several months or years.
Can surgery be performed to treat amblyopia?
Surgery on the eye muscles is a treatment for strabismus (squint) - it can straighten misaligned eyes. By itself, however, surgery does not usually help the amblyopia.
Amblyopia treatment is usually done before strabismus surgery is considered.
Children who have strabismus surgery under the age of 7 can still develop strabismic amblyopia afterwards, and still need close monitoring and treatment for this.
What happens if amblyopia treatment does not work?
In some cases, treatment for amblyopia may not succeed in substantially improving vision. It is hard to decide to stop treatment, but sometimes it is best for both the child and the family. Children who have amblyopia in one eye and good vision in their other eye, can wear safety glasses and sports goggles to protect the normal eye from injury. As long as the good eye stays healthy, these children function normally in most aspects of society.
Where can I learn more about amblyopia research?
There has and continues to be extensive research into the causes of and optimal treatments for amblyopia. The following are just a few examples of where to go for further reading:
The PEDIG group in the US have published papers on amblyopia treatment, see www.jaeb.org for details.
Interventions for unilateral refractive amblyopia. Cochrane Database Syst Review 2008
Conventional occlusion versus pharmacologic penalization for amblyopia. Cochrane Database Syst Rev. 2009
Interventions for strabismic amblyopia. Cochrane Database Syst Rev. 2011