Amblyopia is the clinical term for lazy eye.  An amblyopic eye is looks normal, but vision is poor, even with corrective glasses.  The extent of vision loss may range from very slight to severe. Amblyopia occurs when an infant's or child's vision system in one eye does not completely work together with the brain. The eye is not being used normally because the brain is favoring the other eye. This is often due to the brain suppressing a blurred or double image, caused by strabismus (eye turning in or out), anisometropia (excess difference in glasses prescription between the 2 eyes) or blockage in the line of vision.  Strabismus in a pre-verbal child can be diagnosed by determining which eye the child prefers.  If the child prefers looking at objects with one eye, then the fellow eye is the amblyopic eye.  Focusing devices such as brightly colored objects or toys and other eye covering tests are used for this purpose. If anisometropia is the underlying cause, the eye with the uncorrected larger refractive error usually becomes amblyopic.  Anisometropia is often diagnosed by two to three years of age by different techniques, depending on the cooperation of the child.

Amblyopia affects approximately 2 out of every 100 children and develops sometime between birth and 8 or 9 years of age. This is the critical time period when the visual system develops and matures.  Amblyopia must be identified and usually needs to be treated by 8 or 9 years of age, or the vision loss becomes irreversible.  Even with successful treatment, amblyopia may recur if treatment is discontinued before 10 years of age. In many cases, the pediatrician or other health care provider is the first to suspect amblyopia during a visual acuity screening test at age three.  If there is any suspicious of abnormal vision, the child is typically referred for an ophthalmic and amblyopic evaluation.

The most common and successful treatment of amblyopia may be to cover or patch the better eye, either full or part-time, until vision in the amblyopic eye recovers to the same level as the normal eye.  As a general rule, one-week of full-time patching is required for every year of life.  For example, a three year old with amblyopia in the right eye should wear a patch over the left eye for three weeks, and then be re-evaluated.  This guideline is a conservative estimate, since most children must wear a patch for a longer time to achieve a full recovery.  A recent study has determined that amblyopia may also be successfully treated with eye drops to slightly blur the near vision of the non-amblyopic eye, which forces the amblyopic eye to focus on objects, especially at near. The drops are used daily until vision in the amblyopic eye is the same or nearly the same as the vision in the opposite eye. The extent of the recovery, if any, depends on the age when the treatment is started and the underlying cause of the amblyopia.  Many children also require glasses as part of their visual therapy.  This is usually determined by examining the child's eyes while they are dilated.

Patching the eye during visual activities

Some children do not tolerate patching because vision in the amblyopic eye is so poor that they continually remove the patch from the "good" eye.  For others, the adhesive in the patch may cause irritation.  In these cases, an alternative method of occlusion may be recommended such as a "pirate's patch," (some children enjoy wearing this type), occlusive or opaque tape on the spectacle lens of the better eye.  It is important for the child to use the amblyopic eye during times of maximum visual stimulus, such as during reading, watching television or drawing and not at bed time. Generally, the earlier the amblyopic treatment is initiated, the better the prognosis for correcting the amblyopia. Parent's cooperation and assistance in helping their child through amblyopia therapy is very important in determining the final outcome of the treatment.

Amblyopia associated with strabismus cannot be corrected only by strabismus surgery (realignment of the eyes).  Patching or eye drops therapy to reverse the amblyopia is generally completed first.  Strabismus surgery is performed afterward to improve eye alignment.  Some children require additional amblyopia therapy following strabismus surgery.