Lazy Eye Health Article

Definition

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.

Description

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.

Causes & symptoms

The following are probable causes of lazy eye:

• Strabismus, or misalignment of a child's eyes (crossed eyes). This is the most frequent cause of lazy eye. Approximately half of all children with crossed eyes will develop a lazy eye. In children with crossed eyes, the images do not coordinate, thus confusing the brain. Therefore, the brain will suppress the image that comes from one eye and predominantly use the image from the stronger eye.
• Anisometropia (unequal refractive power). In this case, there is difference in image quality between the two eyes because one eye is severely nearsighted or farsighted. In other words, one eye focuses better than the other. The brain will mostly use the clearer image from the good eye. The other eye will become underdeveloped due to neglect.

• Congenital cataract. The lazy eye can not see well because its lens is already cloudy at birth.
• Ptosis (drooping eyelid). Vision in the lazy eye is blocked or impaired by the drooping eyelid.
• Corneal scarring. The image quality of the affected eye is poor due to scarring in the cornea.

The following are risk factors for amblyopia:

• rubella (German measles) or other infections in the mother during pregnancy
• premature birth
• other family members with vision problems in childhood

Lazy eye may not present obvious symptoms. For this reason, it is important for small children to have regular eye examinations.

Diagnosis

Diagnosis of amblyopia is often made during visual screening during routine infant check-ups and in the preschool years (aged three to five). Premature babies need to have more frequent eye exams during early childhood to prevent this and other vision problems. A new photoscreening instrument that has been recently introduced appears to significantly increase the accuracy of diagnosis of these eye problems.

Treatment

The following alternative methods may complement conventional treatment of lazy eye. However, they are not replacements for conventional treatments. Because their effectiveness is not proven, parents should consult their child's ophthalmologist about the appropriate use of these methods (if any) in their child's overall eye treatment program.

Orthoptics (eye exercises)

Eye exercises can be helpful. Orthoptic exercises are designed to help the eyes move together and assist the fusing of the two images seen by the eyes. It can help correct faulty vision habit due to misalignment of the eyes and can teach the child to use both eyes effectively and comfortably. This form of therapy can be used before or after eye-realignment surgery to improve results.

Vision therapy

Vision training is a form of physical therapy for the brain and the eyes. It is a more extensive form of eye exercise and requires more frequent visits.