Amblyopia
Amblyopia (often referred to as “lazy eye”) is a developmental disorder beginning in childhood where a perfectly healthy eye is unable to be corrected to 20/20 even with glasses. Two ocular conditions, when left untreated as a child, are primary risk factors fo
r the development of amblyopia. These are anisometropia (a large difference in prescription between the two eyes) and strabismus (an “eye turn”).
Risk factors
- Anisometropia
The two eyes cannot focus independently. So if a person’s prescription is vastly different between the two eyes, the brain will receive a constantly clearer image from one eye than the other. For the eye with the clearer image, its visual pathway will develop normally. However, for the eye with the more blurry image, its visual pathway will be developmentally slowed, causing the visual pathway to the brain to not develop the connections necessary to resolve perfect 20/20 vision even with glasses.
A child with anisometropia will often claim to parent that they see just fine, but this is only because they are only using the better seeing eye, many times without even being aware of it. More often than not parents do not even realize that their child is only seeing well with only one of their eyes.
- Strabismus
The brain does not like to see double. So in the case of a child with an eye turn, the brain will suppress the eye creating the second image. If the eye turn is constant, this constant suppression will stunt the development of the visual pathway from that eye to the brain. And as in the case where there is a large prescription difference between the two eyes, this suppression over the course of enough years will lead to an eye that cannot be correctable to 20/20. Although many times an eye turn in a child requires only glasses to correct the turn, surgical intervention is sometimes required.
Treatment
The earlier the diagnosis, the better the chance of being able to restore the ability to see 20/20. This is why it is recommended that a child’s first eye exam be by age 6 months. The longer the anisometropia or strabismus is allowed to persist uncorrected, the greater the chance that the person will never be correctable to 20/20. Although studies vary, if diagnosed and corrected by age 8 permanent amblyopia can be prevented with glasses or muscle surgery alone. After age 8, often several years of vision therapy (such as patching the better seeing eye) is required to regain 20/20 vision in the amblyopic eye. After about age 15, even though vision therapy can still improve the level of vision in an amblyopic eye, perfect 20/20 vision is not likely to be achieved.
Diagnosing amblyopia, and its risk factors, early is key at preventing permanent vision loss. Amblyopia can not only limit career choices, but also increase the risk of profound vision disability if illness or injury should ever affect the better seeing eye. Amblyopia is preventable only if caught early. For these reasons, it is strongly recommended that children have their first eye exam by age 6 months and yearly thereafter.
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