What is amblyopia?
The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.
Amblyopia is the most common cause of visual impairment in childhood. The condition affects approximately 2 to 3 out of every 100 children. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children and young and middle-aged adults.
Amblyopia may be caused by any condition that affects normal visual development or use of the eyes. Amblyopia can be caused by strabismus, an imbalance in the positioning of the two eyes. Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Sometimes amblyopia is caused when one eye is more nearsighted, farsighted, or astigmatic than the other eye. Occasionally, amblyopia is caused by other eye conditions such as cataract.
Treating amblyopia involves making the child use the eye with the reduced vision (weaker eye). Currently, there are two ways used to do this:
A drop of a drug called atropine is placed in the stronger eye once a day to temporarily blur the vision so that the child will prefer to use the eye with amblyopia. Treatment with atropine also stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.
An opaque, adhesive patch is worn over the stronger eye for weeks to months. This therapy forces the child to use the eye with amblyopia. Patching stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.
Previously, eye care professionals often thought that treating amblyopia in older children would be of little benefit. However, surprising results from a nationwide clinical trial show that many children age seven through 17 with amblyopia may benefit from treatments that are more commonly used on younger children. This study shows that age alone should not be used as a factor to decide whether or not to treat a child for amblyopia.
Studies are very limited at this time and scientists don’t know what the success rate might be for treating amblyopia in adults. During the first six to nine years of life, the visual system develops very rapidly. Complicated connections between the eye and the brain are created during that period of growth and development. Scientists are exploring whether treatment for amblyopia in adults can improve vision.
Findings from the clinical study, An Evaluation Of Treatment Of Amblyopia In Children 7 To (less than) 18 Years Old (ATS3), show that many children age seven through 17 with amblyopia (lazy eye) may benefit from treatments that are more commonly used on younger children. Previously, eye care professionals often thought that treating amblyopia in older children would be of little benefit.
The NEI is currently supporting the Amblyopia Treatment Study: Occlusion Versus Pharmacologic Therapy for Moderate Amblyopia (ATS) to determine whether patching or eyedrops is a better treatment for amblyopia. Recent results for the ATS found that the atropine eyedrops, when placed in the unaffected eye once a day, work as well as eye patching and may encourage better compliance. The study was conducted at 47 clinical sites throughout North America.
In addition, A Randomized Trial Comparing Part-time Versus Minimal-time Patching for Moderate Amblyopia (Two v. Six) is being conducted to determine whether the visual acuity improvement obtained with part-time (6 hours) patching is equivalent to the visual acuity improvement obtained with minimal patching (2 hours) for moderate amblyopia. Recent findings show that patching the unaffected eye of children with moderate amblyopia for two hours daily works as well as patching the eye for six hours. Shorter patching time should lead to better compliance with treatment and improved quality of life for children with amblyopia.
Courtesy: National Eye Institute, National Institutes of Health (NEI/NIH)