Both eyes must receive clear images during the critical period of birth to 6 years of age. Anything that interferes with clear vision in either eye during this critical period can result in amblyopia.

The most common causes of amblyopia are constant strabismus (turn of one eye), anisometropia (different vision/prescriptions in each eye), and/or blockage of an eye due to trauma, lid droop, congenital cataracts, etc.

If one eye sees clearly and the other sees a blur, the good eye and brain will inhibit (block, suppress, ignore) the eye with the blur. The good eye becomes stronger, suppressing the image of the other eye. Thus, amblyopia is a neurologically active process. The inhibition process (suppression) can result in a permanent decrease in vision that cannot be corrected with glasses, lenses, or LASIK surgery, rendering the weaker eye useless.

Early treatment is usually simple, employing glasses, drops, vision therapy, and/or using an eye patch. Detection and correction before the age of two offers the best chance for a cure.

According to current research, amblyopia cannot be cured (to normal 20/20 stereo vision) without early detection and treatment. However, treatment for older children and adults is usually successful in improving vision and should be attempted. Treatment of amblyopia in older children and adults requires more effort, including vision therapy. Regardless of age, every amblyopic patient deserves an attempt at treatment.