Amblyopia Amblyopia is a condition in which vision in an otherwise normal eye is poor. It occurs because the brain and the affected eye are not working together properly, causing the brain to ignore the images from that eye. The condition is sometimes called "lazy eye."

The American Academy of Ophthalmology estimates two to three percent of Americans have amblyopia. It has three main causes. The most common cause of amblyopia is strabismus, or misaligned (crossed) eyes. When one eye is not properly aligned, the brain gets mixed signals from the two eyes. The brain accommodates by turning "off" the vision from the misaligned eye and only using the information coming from the "good" eye. As a result, vision fails to develop in the misaligned eye.

Refractive errors are vision problems that cause nearsightedness, farsightedness or astigmatism. Amblyopia can occur when refractive errors affect one eye or when there is a difference in refractive error between the two eyes. The images that are more blurred are turned off by the brain.

Cloudiness of the lens (such as with a cataract) can prevent clear images from reaching the retina and being transmitted to the brain. The problem can also occur with any type of light deprivation to one eye, interfering with the ability of the brain to interpret information coming into that eye.

Amblyopia interferes with the development of normal, equal vision. Eventually, the brain may not use the affected eye to see and patients have good vision in only one eye. In adults, the condition is not treatable, even with corrective lenses, because the pathways between the brain and the eyes have already been established. Employment choices may be more limited because some occupations require good vision in both eyes. In addition, if the healthy eye is ever injured, the patient may be left with limited vision.

Treating Amblyopia To establish healthy vision, the brain must learn to work with and properly process information coming from both eyes. Thus, a child with amblyopia must make use of the "weaker" eye. To accomplish this, doctors may recommend patching of the "good" eye for several weeks to months. Patching forces the brain to use the images coming from the weak eye and strengthens the brain-eye connection. An alternative to patching is a medication called atropine. A drop of atropine placed in the good eye temporarily blurs the vision in that eye, forcing the child to use the weaker eye. In some cases, corrective lenses may be required to improve the clarity of images coming into the weaker eye. If a medical condition, like cataract, is causing the problem, the clouded lens must be removed and replaced with an intraocular lens, contact lens, or eyeglasses.

Detecting Amblyopia The earlier amblyopia can be detected, the greater the likelihood the condition can be reversed and vision restored. The American Academy of Ophthalmology recommends vision screening for all children between 3 and 3 ½ and a full testing of visual acuity by 5. Younger children (6 months to one year) should have a physical exam to assess ocular health (to look for signs of disease, like cataract).

Since early intervention is so important to develop healthy vision, researchers would like to detect signs of vision problems even earlier. However, since infants and small children are unable to respond to examiners, standard eye tests aren't useful.

Researchers have developed a new type of screening test to detect potential vision problems in children as young as six months. It's called the Enfant™ Pediatric Vision Testing System (DIOPHYSIS™). The test measures the brain's response to visual stimuli.

To use the test, three small electrodes are placed on the child's head. When the test is started, cartoon characters appear on a video display and music plays. Six attention-getting stimuli appear on the screen. The electrodes measure the responses from the brain (brain wave activity) and processes the information. Scientists have established that when a person is presented with visual stimuli, certain areas of the brain become more active with characteristic brain waves. This is an electrical response in the brain, or visual evoked potential (VEP). A computer compares the child's VEP with known standards and presents the results in a graphic and numeric formula. That data helps to detect potential refractive errors, like nearsightedness and farsightedness. The computer also compares the VEP from each eye to provide information about any discrepancies in the visual pathways (which could be an indication of amblyopia). Testing time is only about 36 seconds.

The Enfant™ Pediatric Vision Testing System is recommended for children six months and older. Currently, researchers are using the test on children up to age five or six, when they become old enough to participate in standard eye examinations.

For information about the eye test and a link to sites: DIOPSYS™, http://www.diopsys.doc

For general information about amblyopia and other vision problems in children: American Academy of Ophthalmology, public website, http://www.medem.com National Eye Institute, http://www.nei.nih.gov Prevent Blindness America, http://www.preventblindness.org