Amblyopia, often called lazy eye, is a condition that negatively affects the vision in only one of the patient’s eyes.  This reduced vision is a result of reduced visual development due to one of, or a combination of, factors.  Amblyopia usually develops during early childhood (birth to 7 years) and is the leading cause of decreased vision amongst children.  

Causes of amblyopia

Amblyopia usually develops due to an inability for the patient’s two eyes to work together properly.  Ideally both eyes should be aligned with their visual target and deliver similar visual inputs to the brain which can then be processed into a single image.  If for whatever reason the visual input from the two eyes differ significantly, the brain will not be able to combine these visual inputs.  In these cases, there will usually be a stronger eye that develops normally and a weaker eye which is then suppressed and becomes amblyopic due to decreased visual stimulation and development.

Several reasons might cause the two eyes not to work together properly.  An imbalance in the muscles responsible for eye movements might cause a misalignment of the eyes, resulting in one eye being aligned with the visual target, while the other eye remains misaligned.  This would then result in suppression of the misaligned eye and amblyopia development.

A large difference in the clarity of vision between the two eyes can also prevent them from working together.  If one eye has a much higher refractive error than the other eye, this will result in a difference in clarity between the eyes and the weaker eye might become suppressed, once again leading to amblyopia. 

A final possible reason that amblyopia might develop is due to deprivation of visual stimulation from one eye altogether.  A congenital (from birth) cataract could result in this type of deprivation and the eye would develop amblyopia due to a lack of visual stimulation and development. 

Treatment and prevention of amblyopia

Early detection and intervention could help prevent amblyopia from developing.  Intervention include optical correction such as glasses or contact lenses, patching of one of the eyes to provide visual stimulation to the other, therapy, as well as several other possible strategies.  Amblyopia that has already developed can also be reversed if treatment is initiated during the crucial developmental period. Various studies have shown visual improvement in eyes with amblyopia when appropriate treatment strategies are followed.  While early detection is key in the positive treatment of amblyopia, studies have also shown that older persons with amblyopia might also respond positively to treatment.  

Conclusion

Amblyopia is the most common cause for visual loss in children and can cause permanent visual loss if left unaddressed.  Several factors could lead to the development of amblyopia and early detection is crucial in the prevention or treatment of this condition.  For this reason, it is important that children are seen by an optometrist or ophthalmologist at an early age.