The term "lazy eye" refers to the condition amblyopia. An estimated 2-4 percent of children under age 6 have the condition--an underdeveloped nerve pathway from the eye to the visual processing center of the brain, the occipital cortex.

Amblyopia can be due to a muscle weakness, leading to a crossed or wandering eye; or to a large difference in eyeglass prescription between the two eyes.

Normally the images sent by each eye to the brain are identical. When one eye is turned or not in focus, two different images or double vision occurs. Rather than go through life with double vision, the brain learns to ignore the information from the abnormal eye. This affects the central vision. Peripheral vision is not compromised by amblyopia.

Current theory concludes that since signals from the weak eye are being actively suppressed by the brain, the optic nerve is not getting fully stimulated and the neural pathways never fully develop.

The underlying problem can be very subtle and not apparent to parents or teachers. For instance, one eye that is more near or farsighted may have no symptoms at all or just a slight decrease in depth perception.

If this problem isn’t corrected by about age six, the nervous system soon loses its ability to develop fully. Amblyopia is one of the main reasons we want to examine children by age three so treatment can be successful while the nervous system is still growing.

Symptoms may include:

• Covering one eye when reading
• A constant head turn.
• Bumping into objects or general clumsiness
• Among very young children, a strong objection to having their "good" eye covered.
• Risk factors such as family history of amblyopia or eye muscle misalignment.

Routine school visual screenings can miss amblyopia if it is subtle or if the child is not 100 percent cooperative. A complete annual exam with an eye doctor should involve reviewing of eye disease risk factors and family history, closely checking eye-muscle alignment, checking depth perception, determining whether eye glasses are needed or the prescription needs changing, and performing a general eye exam with pupils dilated.

Treatment of amblyopia can involve glasses or contact, patching the good eye, eye exercises or eye-muscle surgery to correct the misalignment. Fortunately, the earlier amblyopia is diagnosed, the quicker and more complete the cure.

The biggest concern with discovering amblyopia when it’s already too late in the chance of an accident or disease later in life that affects a person’s only good eye, leaving them handicapped. This can vary from the inconvenience of mild amblyopia to legal blindness, leading to job loss and lifestyle changes.

The saying "Prevention is the best medicine" is especially true in checking kid’s vision at ages three, five and then annually throughout the school years.