Amblyopia is a medical condition in which one or both eyes see suboptimally because vision did not develop normally during infancy and/or childhood. If clear images are not transmitted from the eye(s) to the appropriate portions of the brain, the brain will underuse one or both eyes. The most important time for visual development is during the first two years of life, but the potential for visual maturation continues through approximately age nine. Although treatment can produce improved visual results after age nine, improvement in corrected vision is much more limited because the visual system between the eyes and the brain has already completed most of its development. Amblyopia, present in 1 to 4% of children, is the number one cause of decreased vision among the youth. Children should be evaluated early and commence treatment as soon as possible in order to achieve the best possible vision.
TYPES OF AMBLYOPIA
Refractive amblyopia represents the most common cause of improper vision development and results when the refractive error (farsightedness, nearsightedness, and/or astigmatism) of one or both eyes is not corrected at all or is inadequately corrected during the critical time of visual maturation. The brain favors the eye with the smaller refractive error. It occurs at a lower uncorrected level of farsightedness than of nearsightedness since nearsighted children can bring objects closer to them to see.
Strabismic amblyopia may develop if eye misalignment is left untreated. If one of a child’s eyes is not aligned with fixation targets during visual development, then visual information does not enter the misaligned eye or reach the brain as it does from the fixating eye during a critical time period. When the eyes are not aligned together, each eye of a non-amblyopic adult would see a separate image, but children typically suppress the image from the misaligned eye, and the brain ignores the visual stimulation from that eye.
Both refractive and strabismic amblyopia often develops because a refractive error is not addressed properly and the poorly seeing eye becomes misaligned.
Deprivation amblyopia, the most severe kind of lazy eye, occurs because the visual pathway is blocked, for example, by a droopy lid, a centrally opaque cornea, a malformed or scarred iris, or a cataract (usually central and greater than 3mm in diameter). Any condition which impedes vision in young children should be treated promptly to minimize the risk of developing amblyopia.
Amblyopia generally must be treated by age nine in order to be effective. Although treatment can still produce improved visual results after age nine, improvement is much more limited since the visual system between the eyes and the brain has already completed most of its development.
Treatment can include some combination of eye glasses, contact lens(es), patching, medication (usually atropine 1% eye drops), and a fogging lens (in glasses or with a contact lens).
Glasses or Contact Lenses Alone
If the child has bilateral amblyopia because of a significant symmetrical uncorrected refractive error, full time glasses or contact lens wear is the solution. If there is inequality between the best-corrected vision of the eyes, then a patching/eyedrop/fogging lens regimen (one or all) applied to the good eye stimulates the brain to use the affected “lazy” eye, especially with the correct lens over it to make the image as clear as possible.
Patching the stronger eye forces the child to use and strengthen the amblyopic eye. The patch can be applied to the skin with glasses over it. Alternatively, patches which slide over a lens of glasses, but which block seeing above, below, and to the sides, can be used. It is important not to select a patch that the child can see through or peek around.
This method most commonly entails instilling one drop of atropine 1% on the better seeing eye at bedtime (although variations of this may be recommended). It is typically easier than patching. This can be prescribed in conjunction with the correct glasses prescription for each eye, with patching, or with a fogging lens for one eye in more severe or recalcitrant cases.
Determining the appropriate treatment plan for amblyopia depends on a multitude of factors and may change based on the child’s response. Dr. Shin will discuss treatment options and make recommendations during your child’s visits.