A person with amblyopia, or "lazy eye", has a condition in which the message sent from the affected eye or eyes to the brain is of low quality, making the sight of that eye poor. Sometimes the phrase "dimness of vision" is used to describe Amblyopia. A person with Amblyopia will have poor vision that cannot be corrected simply with spectacles.
Amblyopia has many different causes. Generally, if a person cannot use both eyes together when they are young, one eye may become amblyopic. Common causes of this are a turned eye or a large difference in the extent of short-sightedness, long-sightedness or astigmatism (refractive error) between a person's eyes. Rare causes of Amblyopia can include disease or injury to the nerve connecting the eye to the brain, some psychiatric conditions and excessive use of tobacco, alcohol or other drugs.
Although the basic components of the visual system are present at birth, a child's visual system continues to develop after birth in response to his or her visual environment. This development progresses rapidly in the first few years of life and continues until at least the age of seven years. Normally the message sent to the brain from both eyes is the same. In a person with Amblyopia, the message received be the brain from one eye is different from the message from the other eye, either because it is out of focus or because the eyes are pointing in different directions. The brain compensates for this difference by ignoring the message from the worse eye. If a child's visual system is not corrected early in life, the child may never develop the ability to process the image from the worse eye.
Up to four per cent of the population have amblyopia.
The most important sign is poor vision but because only one eye is affected and the other eye usually does the work of both, often parents are unaware of the problem. Other clues are a noticeable favouring of one eye, a "turned" eye and bumping into objects on one side of the body. A thorough eye examination is the only sure way of determining whether your child has amblyopia. If you think that there may be something wrong with your child's vision, discuss it with your optometrist.
The treatment depends on the particular cause of the amblyopia. Most commonly glasses, prisms, contact lenses and vision therapy programs are used to train the poor eye to function normally. Sometimes the better eye is covered with a patch to force the person to use and strengthen the lazy eye. Some special or rare types of amblyopia are treated simply by improving the person's general health. The earlier amblyopia is detected, the easier it is to treat.