Lazy eye, or amblyopia, is an eye condition in which disuse causes reduced vision in an otherwise healthy eye. The affected eye is called the lazy eye. This vision defect occurs in 2–3% of American children. If not corrected before age eight, amblyopia will cause significant loss of stereoscopic vision, the ability to perceive three-dimensional depth.
In some children, one eye functions better than the other. When a child begins to depend on the stronger eye, the weaker eye can become progressively weaker. Eventually, the weaker eye grows "lazy" from disuse. If left untreated beyond the early child-development years (from birth to seven years old), vision in the affected eye will be underdeveloped due to lack of use.
The impairment of vision in the lazy eye occurs in three phases. In the first (suspension) phase, the brain turns the weaker eye on and off. In the second (suppression) phase, the brain turns off the lazy eye indefinitely. At this point, the eye still has usable vision and can function well if the other eye is covered. In the last (amblyopia) phase, which occurs after age seven, the eye loses all the sensitivity that is essential for good vision because it has not been used for so long.
Lazy eye is a visual problem with potentially serious consequences. If left untreated, the affected child may have permanent loss of vision in the lazy eye. Because of loss of vision in one eye, these children cannot see three-dimensional images very well—all images appear flat. They also have problems with depth perception. This has serious consequences in their future ability to work in professions that require good vision in both eyes. Affected children also have increased risk of blindness should something happen to the good eye.
Mai Tran, Rebecca J. Frey PhD, The Gale Group Inc., Gale, Detroit,