Amblyopia (lazy eye), means that the eye has not developed normally and always has blurred vision, even with the best spectacle glasses or contact lenses your eye surgeon or the optometrist can prescribe.
Amblyopia is caused when the brain favors one eye and refuses to use the other. Simply stated, amblyopia is a dysfunction of the brain which blocks vision from one eye because it can’t use the two eyes together. Because the eye is "turned off, " clear vision does not develop in the lazy eye. Amblyopia affects 2 to 3 percent of the population.
Amblyopia (lazy eye) is a unilateral or bilateral reduction of corrected visual acuity without any visible defect in the eye commensurate with this loss. It is a common functional defect in children that can be very challenging to treat, caused by vision deprivation, abnormal binocular interaction, or both and for which no organic cause can be detected by physical methods. In many cases, it is reversible by therapeutic measures.
The brains of children who have a lazy eye, however, did not learn to use their two eyes together. At an early age, these children only used one eye, and their brain “turned off” or blocked the in-coming picture from the other eye. Turning off an eye is called suppression. Therefore, a child with a lazy eye not only sees out of just one eye, but as a result he also has poor depth perception and limited side vision in the eye he is suppressing.
Because the brain turned off the lazy eye very early in life, it did not develop normal sharpness of vision, called acuity. Therefore, a lazy eye has very poor eyesight; vision out of the weak eye is blurred. This “use it or lose it” syndrome means that the child has lost the ability to see clearly out of the lazy eye, even with the best pair of glasses or contact lenses, the eye surgeon can prescribe. How poor the vision is in the weak eye depends in part upon how early in the child’s visual development the brain turned the eye off.
Amblyopia is caused by various conditions that prevent the brain from using both eyes together. In some cases, the tendency for a lazy eye may be inherited. One type of lazy eye, called refractive amblyopia, is caused when each eye needs a different prescription, making it difficult for the eyes to focus together. In this situation, the best prescription for glasses or contact lenses is used to help equalize the vision in each eye.
One of the most common causes of a lazy eye, however, is strabismus ( squint ). Strabismus, commonly referred to as a crossed or wandering eye, is a condition in which the brain is unable to properly align the eyes. As a result, one eye may point in or out, up or down. When the eyes are not pointing at the same place, two different pictures are being sent to the brain. Because the brain can’t combine two obviously different pictures into a single image, the result is double vision. The brain is then forced to turn off the picture coming in from the misaligned eye to avoid seeing double. The child only uses his straight eye to see, and vision in the turned eye does not have a chance to develop.
To correct amblyopia, the weak eye must first be forced to work in order to allow the opportunity for clear vision to develop. This is usually done by patching the strong eye for specific periods of time, forcing the weak eye to “turn on” and practice working. Secondly, glasses are prescribed to provide the weak eye with the best support possible. Finally, squint—the underlying cause of the lazy eye in most of the cases must also be corrected.
In addition to glasses, there are three different approaches to the treatment of a lazy eye:
It is imperative that parents of a child with a lazy eye fully understand their treatment options so that they can make the best choice for their child. It is only with their cooperation and active participation that we can get the best results. It is imperative to assess the motivation of the child’s parents. Their understanding and willingness to co-operate in this complicated care of the child is essential if there is to be any hope for useful vision.