Amblyopia – “Lazy Eye”

Birth to Three article by:  Carol E. Marusich, OD, MS, FCOVD

Amblyopia or “Lazy Eye” as it is sometimes called, affects about four million people in the United States.  If left untreated, this condition can interrupt your child’s normal visual development and cause visual dysfunctions that will last a lifetime.

Amblyopia means an inability to see clearly, usually with one eye, which does not immediately improve with eyeglasses or contact lenses.  Amblyopia is diagnosed when eyesight cannot be corrected to at least 20/40 (legal driving vision) even though the eye is healthy and no disease is present.

A number of conditions can cause amblyopia including uncorrected farsightedness, astigmatism or significant nearsightedness; a large difference in refraction between the two eyes; strabismus, where the eyes do not remain properly aligned; and deprivation, where the vision in one eye has been obstructed for a period of time.

Most forms of amblyopia appear early, usually before age six, but a significant, long-term interference in vision of one eye at any age can cause decreased vision.

In all of these situations, something has prevented the child from using the two eyes together as a team.  Rather than allow a distorted picture from one eye to interfere with a good picture from the other eye, these children quickly learn to ignore or suppress the visual input from the blurred eye.  The same is true when the eyes do not align properly.  Rather than have the confusion of seeing double, they learn to pay attention to only one image and eventually suppress the non‑dominant eye which is turned.  It is worth the extra energy it takes to actively block the visual messages from the poorer eye in order to preserve the clearer, single image seen by the dominant eye and avoid confu­sion.  With prolonged disuse, the ability to see clearly through the non-dominant eye gradually diminishes.

In some children, the “Lazy Eye” may wander, alerting parents and care givers that something is wrong.  These children are often examined, diagnosed and treated early, before visual‑motor development is significantly delayed.  Children with amblyopia who’s eyes remain straight even though they are only using one eye for most of their visual tasks may go undetected and untreated through their most important developmental years. Because there are no outward signs, the eyes may look perfectly normal, and these young children are usually unaware that one eye is blurred.  Often in these cases the amblyopia may go unrecognized until the child first enters school unless early testing reveals the difference in function between the two eyes.

How can we prevent amblyopia from interfering with our child’s normal visual development?  Early diagnosis and treatment are our best resources.

Concerned parents can check their family history for amblyopia or the conditions that can predispose a child to devel­op amblyopia.  They can also be alert and watch for symptoms of vision problems in young children such as unusual blinking; winking; poor eye teaming or extreme light sensitivity.  Be aware, however, that both family history and symptoms may be absent in the child with amblyopia.  For that reason it has been recommended that all children have a comprehensive eye examination between six months to one year of age.

With today’s technology and specialized pediatric tests, comprehensive examination of visual acuity, eye health, refractive condition, and eye teaming can be successfully completed on very young infants.  Your child does not need to be old enough to “read the chart” to have an accurate assessment of his or her eyesight and vision development.

What happens when amblyopia is diagnosed?  Once the difference between the two eyes is detected, the underlying cause must be identified and treated.  Glasses or a contact lens may be necessary to correct the refractive condition in one or both eyes.  In addition to refractive correction, treatment may also include the use of prisms, patching or penalization (blocking all or part of the vision of the preferred eye to encourage use of the amblyopic eye), vision therapy activities or a combination of these.

The goal of treatment is to not only encourage the child to develop vision in the amblyopic eye, but to learn to use the two eyes together as a team.  Unless eye teaming (binocularity) is well established, the child will continue to use only the dominant eye out of habit and the amblyopia will return once patching is discontinued.  Results are permanent, however, when both the amblyopia and underlying eye teaming problems are corrected.

For many years doctors thought that amblyopia could not be treated past six years of age.  Current research has conclusively demonstrated that effective treatment can take place at any age, but the length of the treatment period increases dramatically the longer the condition has existed prior to treatment.  The earlier amblyopia is successfully treat­ed, the less likely it is to interfere with your child’s long‑term visual development.  Research has also demonstrated that patients with amblyopia are more likely to sustain injuries resulting in the loss of their better eye than individuals with two good eyes.  This is one of the many reasons that early childhood examinations are essential.