Makindo Medical Notes

Amblyopia results in permanent decreased vision in the pathological eye if not treated early enough, even if the ocular pathology is removed later on in life. It is the most common cause of decreased vision in a single eye among children and younger adults.

About

• Amblyopia is the failure of the normal neurological development required for good visual acuity

Aetiology

• Inadequate visual stimulation during the development of the normal neurological pathway
• Consequences of amblyopia include poor stereovision, visual acuity, pattern recognition, and low sensitivity to motion and contrast
• Failure of development of the neural networks needed for vision and image processing
• MRI shows a decreased visual cortex size in patients with amblyopia.

Causes

• The three major causes of amblyopia are refractive error, strabismus, and media opacity
• By far the most common form is unilateral amblyopia due to refractive difference (anisometropia) between the two eyes
• Hypermetropic anisometropic patients are at much higher risk of amblyopia
• Amblyopia is much less common in myopic patients, focused vision when reading seems protective against the development of amblyopia, even in the context of significant anisometropia
• Causes of media opacity include congenital corneal dystrophies and congenital cataract, these may cause bilateral amblyopia

Clinical

• In many cases, amblyopia may not be picked up until later in life when vision is formally tested for the first time. This is problematic as the child will often have already reached the age where the vision cannot be salvaged
• All forms of amblyopia often need to utilize visual penalization of the non-amblyopic eye to force visual development in the amblyopic eye. The most common form of visual penalization is patching the non-amblyopic eye
• Beyond 8 years old, an amblyopic eye can no longer be saved

Prevention

• Screening is essential to ensure early detection and prevent the development of amblyopia
• All children in the UK should have their vision screened when they first start school at the age of 4. Free annual vision checks are also available to all children of school age.

References

• Amblyopia
• Amblyopia at Stat pearls