Amblyopia ('lazy eye')

Amblyopia means a reduction in an eye's ability to see. It occurs when something disrupts the development of the visual pathway between the eye and the brain, and is the most common visual disorder in children.

Newborn infants have very poor vision. However, as they use their eyes during the first few months of life their vision starts to improve. Children's visual systems continue to develop until about the age of 8. If, in early life, an eye has obstructed or poorly focussed vision, or is misaligned (strabismus), the brain may "switch off" or suppress the signals from this eye and use only the better eye to see, thus failing to develop the vital connection between eye and brain.

It is essential that children with eye problems be treated during these fragile years to prevent or reduce the effects of amblyopia.

Types of amblyopia

• Deprivational amblyopia is caused by something obstructing the passage of light through the eye, most commonly a congenital cataract. A baby with cataracts sees as if looking through a tissue and can only identify light, dark and colour, or very close objects. This is not sufficient to enable good visual development.
• Strabismus can also cause amblyopia. The image from the turned eye is ignored or suppressed by the brain to avoid double vision and confusion.
• Anisometropic amblyopia is a result of untreated poorly focussing eyes. This is may be due to long-sightedness (hypermetropia), short-sightedness (myopia), astigmatism or unequally focussing eyes (anisometropia). The brain suppresses the image from the poorly focussing eye, resulting in arrested development of the visual system.

How can amblyopia be treated?

Untreated amblyopia can lead to permanent visual problems and lack of depth perception. Also, if a person's "good eye" develops disease or is injured later in life, the amblyopic eye will not see well enough to provide adequate vision.

Orthoptists and paediatric ophthalmologists specialise in the treatment of amblyopia. The aim is to correct the vision in the amblyopic eye. If amblyopia is due to a cataract, this should be removed urgently. If it is due to strabismus it can be treated with a combination of eyedrops, glasses, patching and/or eye muscle surgery. Anisometropic amblyopia is treated with glasses to correct the focussing problem.